﻿ Euler Math Toolbox - Reference

## Maxima 5.35.1 Manual

Maxima is a computer algebra system, implemented in Lisp.

Maxima is derived from the Macsyma system, developed at MIT in the
years 1968 through 1982 as part of Project MAC.  MIT turned over a copy
of the Macsyma source code to the Department of Energy in 1982; that
version is now known as DOE Macsyma.  A copy of DOE Macsyma was
maintained by Professor William F. Schelter of the University of Texas
from 1982 until his death in 2001.  In 1998, Schelter obtained
permission from the Department of Energy to release the DOE Macsyma
source code under the GNU Public License, and in 2000 he initiated the
Maxima project at SourceForge to maintain and develop DOE Macsyma, now
called Maxima.

Maxima infrastructure

Introduction to Maxima      Sample Maxima sessions.
Bug Detection and Reporting Finding and reporting bugs in Maxima.
Help                        Asking for help from within a Maxima session.
Command Line                Maxima command line syntax, Input, and Output.
Data Types and Structures   Numbers, Strings, Lists, Arrays, and Structures.
Expressions                 Expressions in Maxima.
Operators                   Operators used in Maxima expressions.
Evaluation                  Evaluating expressions.
Simplification              Simplifying expressions.
Mathematical Functions      Mathematical functions in Maxima.
Maximas Database            Declarations, Contexts, Facts, and Properties.
Plotting                    2D and 3D graphical output.
File Input and Output       File input and output.

Support for specific areas of mathematics
Polynomials                 Standard forms for polynomials, and
functions operating on them.
Special Functions           Special functions
Elliptic Functions          Elliptic Functions and Integrals
Limits                      Limits of expressions.
Differentiation             Differential calculus.
Integration                 Integral calculus.
Equations                   Defining and solving equations.
Differential Equations      Defining and solving differential equations.
Numerical                   Numerical integration, Fourier
transforms, Equations, ODE's, etc.
Matrices and Linear Algebra Matrix operations.
Affine
itensor                     Indicial Tensor Manipulation.
ctensor                     Component Tensor Manipulation.
atensor                     Algebraic Tensor Manipulation.
* Sums Products and Series::    Sums, Products, Taylor and power series.
Number Theory               Number theory.
Symmetries
Groups                      Abstract algebra.

Runtime Environment         Customization of the Maxima environment.
Miscellaneous Options       Options with a global effect on Maxima.
Rules and Patterns          User defined pattern matching and
simplification rules.
Sets                        Manipulation of sets.
Function Definition         Defining functions.
Program Flow                Defining Maxima programs.
Debugging                   Debugging Maxima programs.

alt-display                 Alternative display package.
asympa                      Asymptotic analysis package.
augmented_lagrangian        augmented_lagrangian package.
Bernstein                   Bernstein polynomials.
bode                        Bode gain and phase plots.
clebsch_gordan              Clebsch-Gordan and Wigner coefficients
cobyla                      Nonlinear optimization with inequality constraints.
descriptive                 Descriptive statistics.
diag                        Jordan matrices.
distrib                     Probability distributions.
draw                        A Maxima-Gnuplot interface.
drawdf                      Direction fields with Gnuplot.
dynamics                    3D visualization, animations and dynamical systems.
ezunits                     Dimensional quantities.
f90                         Maxima to fortran translator.
finance                     Financial package.
fractals                    Fractals.
ggf                         Generating function of sequences.
graphs                      Graph theory package.
grobner                     Functions for working with Groebner bases.
impdiff                     Implicit derivatives.
interpol                    Interpolation package.
lapack                      LAPACK functions for linear algebra.
lbfgs                       L-BFGS unconstrained minimization package.
lindstedt                   Lindstedt package.
linearalgebra               Functions for linear algebra.
lsquares                    Least squares.
makeOrders                  Polynomial utility.
minpack                     MINPACK functions for minimization and roots
mnewton                     Newton's method.
opsubst                     Substitutions utility.
orthopoly                   Orthogonal polynomials.
romberg                     Romberg method for numerical integration.
simplex                     Linear programming.
simplification              Simplification rules and functions.
solve_rec                   Linear recurrences.
stats                       Statistical inference package.
stirling                    Stirling formula.
stringproc                  String processing.
to_poly_solve               to_poly_solve package.
unit                        Units and dimensions package.
zeilberger                  Functions for hypergeometric summation.

Index
* Function and Variable Index:: Index.

--- The Detailed Node Listing ---

Introduction
Introduction to Maxima

Bugs
Bug Detection and Reporting

Help
Documentation
Functions and Variables for Help

Command Line
Introduction to Command Line
Functions and Variables for Command Line
Functions and Variables for Display

Data Types and Structures
Numbers
Strings
Constants
Lists
Arrays
Structures

Expressions
Introduction to Expressions
Nouns and Verbs
Identifiers
Inequality
Functions and Variables for Expressions

Operators
Introduction to operators
Arithmetic operators
Relational operators
Logical operators
Operators for Equations
Assignment operators
User defined operators

Evaluation
Functions and Variables for Evaluation

Simplification
Functions and Variables for Simplification

Mathematical Functions
Functions for Numbers
Functions for Complex Numbers
Combinatorial Functions
* Root Exponential and Logarithmic Functions::
Trigonometric Functions
Random Numbers

Maximas Database
Introduction to Maximas Database
Functions and Variables for Properties
Functions and Variables for Facts
Functions and Variables for Predicates

Plotting
Introduction to Plotting
Plotting Formats
Functions and Variables for Plotting
Plotting Options
Gnuplot Options
Gnuplot_pipes Format Functions

File Input and Output
Files
Functions and Variables for File Input and Output
Functions and Variables for TeX Output
Functions and Variables for Fortran Output

Polynomials
Introduction to Polynomials
Functions and Variables for Polynomials

Special Functions
Introduction to Special Functions
Bessel Functions
Airy Functions
Gamma and factorial Functions
Exponential Integrals
Error Function
Struve Functions
Hypergeometric Functions
Parabolic Cylinder Functions
Functions and Variables for Special Functions

Elliptic Functions
Introduction to Elliptic Functions and Integrals
Functions and Variables for Elliptic Functions
Functions and Variables for Elliptic Integrals

Limits
Functions and Variables for Limits

Differentiation
Functions and Variables for Differentiation

Integration
Introduction to Integration
Functions and Variables for Integration

Equations
Functions and Variables for Equations

Differential Equations
Introduction to Differential Equations
Functions and Variables for Differential Equations

Numerical
Introduction to fast Fourier transform
Functions and Variables for fast Fourier transform
Functions for numerical solution of equations
Introduction to numerical solution of differential equations
Functions for numerical solution of differential equations

Matrices and Linear Algebra
Introduction to Matrices and Linear Algebra
* Dot::
* Vectors::
* eigen::
Functions and Variables for Matrices and Linear Algebra

Affine
Introduction to Affine
Functions and Variables for Affine

itensor
Introduction to itensor
Functions and Variables for itensor

ctensor
Introduction to ctensor
Functions and Variables for ctensor

atensor
Introduction to atensor
Functions and Variables for atensor

Sums, Products, and Series
Functions and Variables for Sums and Products
Introduction to Series
Functions and Variables for Series
Introduction to Fourier series
Functions and Variables for Fourier series

Number Theory
Functions and Variables for Number Theory

Symmetries
Introduction to Symmetries
Functions and Variables for Symmetries

Groups
Functions and Variables for Groups

Runtime Environment
Introduction for Runtime Environment
Interrupts
Functions and Variables for Runtime Environment

Miscellaneous Options
Introduction to Miscellaneous Options
Share
Functions and Variables for Miscellaneous Options

Rules and Patterns
Introduction to Rules and Patterns
Functions and Variables for Rules and Patterns

Sets
Introduction to Sets
Functions and Variables for Sets

Function Definition
Introduction to Function Definition
Function
Macros
Functions and Variables for Function Definition

Program Flow
Lisp and Maxima
Garbage Collection
Introduction to Program Flow
Functions and Variables for Program Flow

Debugging
Functions and Variables for Debugging

alt-display
Introduction to alt-display
Functions and Variables for alt-display

asympa
Introduction to asympa
Functions and variables for asympa

augmented_lagrangian
Functions and Variables for augmented_lagrangian

Bernstein
Functions and Variables for Bernstein

bode
Functions and Variables for bode

clebsch_gordan
Functions and Variables for clebsch_gordan

cobyla
Introduction to cobyla
Functions and Variables for cobyla
Examples for cobyla

contrib_ode
Introduction to contrib_ode
Functions and Variables for contrib_ode
Possible improvements to contrib_ode
Test cases for contrib_ode
References for contrib_ode

descriptive
Introduction to descriptive
Functions and Variables for data manipulation
Functions and Variables for descriptive statistics
Functions and Variables for statistical graphs

diag
Functions and Variables for diag

distrib
Introduction to distrib
Functions and Variables for continuous distributions
Functions and Variables for discrete distributions

draw
Introduction to draw
Functions and Variables for draw
Functions and Variables for pictures
Functions and Variables for worldmap

drawdf
Introduction to drawdf
Functions and Variables for drawdf

dynamics
The dynamics package
Graphical analysis of discrete dynamical systems
Visualization with VTK

ezunits
Introduction to ezunits
Introduction to physical_constants
Functions and Variables for ezunits

f90
Functions and Variables for f90

finance
Introduction to finance
Functions and Variables for finance

fractals
Introduction to fractals
Definitions for IFS fractals
Definitions for complex fractals
Definitions for Koch snowflakes
Definitions for Peano maps

ggf
Functions and Variables for ggf

graphs
Introduction to graphs
Functions and Variables for graphs

grobner
Introduction to grobner
Functions and Variables for grobner

impdiff
Functions and Variables for impdiff

interpol
Introduction to interpol
Functions and Variables for interpol

lapack
Introduction to lapack
Functions and Variables for lapack

lbfgs
Introduction to lbfgs
Functions and Variables for lbfgs

lindstedt
Functions and Variables for lindstedt

linearalgebra
Introduction to linearalgebra
Functions and Variables for linearalgebra

lsquares
Introduction to lsquares
Functions and Variables for lsquares

makeOrders
Functions and Variables for makeOrders

minpack
Introduction to minpack
Functions and Variables for minpack

mnewton
Introduction to mnewton
Functions and Variables for mnewton

numericalio
Introduction to numericalio
Functions and Variables for plain-text input and output
Functions and Variables for binary input and output

opsubst
Functions and Variables for opsubst

orthopoly
Introduction to orthogonal polynomials
Functions and Variables for orthogonal polynomials

romberg
Functions and Variables for romberg

simplex
Introduction to simplex
Functions and Variables for simplex

simplification
Introduction to simplification
Package absimp
Package facexp
Package functs
Package ineq
Package rducon
Package scifac
Package sqdnst

solve_rec
Introduction to solve_rec
Functions and Variables for solve_rec

stats
Introduction to stats
Functions and Variables for inference_result
Functions and Variables for stats
Functions and Variables for special distributions

stirling
Functions and Variables for stirling

stringproc
Introduction to string processing
Functions and Variables for input and output
Functions and Variables for characters
Functions and Variables for strings

to_poly_solve
Functions and Variables for to_poly_solve

unit
Introduction to Units
Functions and Variables for Units

zeilberger
Introduction to zeilberger
Functions and Variables for zeilberger


## 1 Introduction to Maxima

Start Maxima with the command "maxima".  Maxima will display version
information and a prompt.  End each Maxima command with a semicolon.
End the session with the command "quit();".  Here's a sample session:

[wfs@chromium]$maxima Maxima 5.9.1 http://maxima.sourceforge.net Using Lisp CMU Common Lisp 19a Distributed under the GNU Public License. See the file COPYING. Dedicated to the memory of William Schelter. This is a development version of Maxima. The function bug_report() provides bug reporting information. (%i1) factor(10!); 8 4 2 (%o1) 2 3 5 7 (%i2) expand ((x + y)^6); 6 5 2 4 3 3 4 2 5 6 (%o2) y + 6 x y + 15 x y + 20 x y + 15 x y + 6 x y + x (%i3) factor (x^6 - 1); 2 2 (%o3) (x - 1) (x + 1) (x - x + 1) (x + x + 1) (%i4) quit(); [wfs@chromium]$

Maxima can search the info pages.  Use the describe' command to show
information about the command or all the commands and variables
containing a string.  The question mark ?' (exact search) and double
question mark ??' (inexact search) are abbreviations for describe':

(%i1) ?? integ
0: Functions and Variables for Elliptic Integrals
1: Functions and Variables for Integration
2: Introduction to Elliptic Functions and Integrals
3: Introduction to Integration
4: askinteger  (Functions and Variables for Simplification)
5: integerp  (Functions and Variables for Miscellaneous Options)
6: integer_partitions  (Functions and Variables for Sets)
7: integrate  (Functions and Variables for Integration)
8: integrate_use_rootsof  (Functions and Variables for Integration)
9: integration_constant_counter  (Functions and Variables for
Integration)
10: nonnegintegerp  (Functions and Variables for linearalgebra)
Enter space-separated numbers, all' or none': 5 4

-- Function: integerp (<expr>)
Returns true' if <expr> is a literal numeric integer, otherwise
false'.

integerp' returns false if its argument is a symbol, even if the
argument is declared integer.

Examples:

(%i1) integerp (0);
(%o1)                         true
(%i2) integerp (1);
(%o2)                         true
(%i3) integerp (-17);
(%o3)                         true
(%i4) integerp (0.0);
(%o4)                         false
(%i5) integerp (1.0);
(%o5)                         false
(%i6) integerp (%pi);
(%o6)                         false
(%i7) integerp (n);
(%o7)                         false
(%i8) declare (n, integer);
(%o8)                         done
(%i9) integerp (n);
(%o9)                         false

askinteger (<expr>, integer)' attempts to determine from the
assume' database whether <expr> is an integer.  askinteger'
prompts the user if it cannot tell otherwise, and attempt to
install the information in the database if possible.  askinteger
(<expr>)' is equivalent to askinteger (<expr>, integer)'.

askinteger (<expr>, even)' and askinteger (<expr>, odd)'
likewise attempt to determine if <expr> is an even integer or odd
integer, respectively.

(%o1)                                true

To use a result in later calculations, you can assign it to a
variable or refer to it by its automatically supplied label.  In
addition, %' refers to the most recent calculated result:

(%i1) u: expand ((x + y)^6);
6        5       2  4       3  3       4  2      5      6
(%o1) y  + 6 x y  + 15 x  y  + 20 x  y  + 15 x  y  + 6 x  y + x
(%i2) diff (u, x);
5         4       2  3       3  2       4        5
(%o2) 6 y  + 30 x y  + 60 x  y  + 60 x  y  + 30 x  y + 6 x
(%i3) factor (%o2);
5
(%o3)                      6 (y + x)

Maxima knows about complex numbers and numerical constants:

(%i1) cos(%pi);
(%o1)                          - 1
(%i2) exp(%i*%pi);
(%o2)                          - 1

Maxima can do differential and integral calculus:

(%i1) u: expand ((x + y)^6);
6        5       2  4       3  3       4  2      5      6
(%o1) y  + 6 x y  + 15 x  y  + 20 x  y  + 15 x  y  + 6 x  y + x
(%i2) diff (%, x);
5         4       2  3       3  2       4        5
(%o2) 6 y  + 30 x y  + 60 x  y  + 60 x  y  + 30 x  y + 6 x
(%i3) integrate (1/(1 + x^3), x);
2 x - 1
2            atan(-------)
log(x  - x + 1)        sqrt(3)    log(x + 1)
(%o3)    - --------------- + ------------- + ----------
6             sqrt(3)          3

Maxima can solve linear systems and cubic equations:

(%i1) linsolve ([3*x + 4*y = 7, 2*x + a*y = 13], [x, y]);
7 a - 52        25
(%o1)              [x = --------, y = -------]
3 a - 8       3 a - 8
(%i2) solve (x^3 - 3*x^2 + 5*x = 15, x);
(%o2)       [x = - sqrt(5) %i, x = sqrt(5) %i, x = 3]

Maxima can solve nonlinear sets of equations.  Note that if you don't
want a result printed, you can finish your command with $' instead of ;'. (%i1) eq_1: x^2 + 3*x*y + y^2 = 0$
(%i2) eq_2: 3*x + y = 1$(%i3) solve ([eq_1, eq_2]); 3 sqrt(5) + 7 sqrt(5) + 3 (%o3) [[y = - -------------, x = -----------], 2 2 3 sqrt(5) - 7 sqrt(5) - 3 [y = -------------, x = - -----------]] 2 2 Maxima can generate plots of one or more functions: (%i1) plot2d (sin(x)/x, [x, -20, 20])$

(%i2) plot2d ([atan(x), erf(x), tanh(x)], [x, -5, 5], [y, -1.5, 2])$(%i3) plot3d (sin(sqrt(x^2 + y^2))/sqrt(x^2 + y^2), [x, -12, 12], [y, -12, 12])$


## 2 Bug Detection and Reporting


Functions and Variables for Bug Detection and Reporting


## 2.1 Functions and Variables for Bug Detection and Reporting

Function: run_testsuite ([<options>])

     Run the Maxima test suite.  Tests producing the desired answer are
considered "passes," as are tests that do not produce the desired
answer, but are marked as known bugs.

run_testsuite' takes the following optional keyword arguments

display_all'
Display all tests.  Normally, the tests are not displayed,
unless the test fails.  (Defaults to false').

display_known_bugs'
Displays tests that are marked as known bugs.  (Default is
false').

tests'
This is a single test or a list of tests that should be run.
Each test can be specified by either a string or a symbol.
By default, all tests are run.  The complete set of tests is
specified by testsuite_files'.

time'
Display time information.  If true', the time taken for each
test file is displayed.  If all', the time for each
individual test is shown if display_all' is true'.  The
default is false', so no timing information is shown.

For example run_testsuite(display_known_bugs = true,
tests=[rtest5])' runs just test rtest5' and displays the test
that are marked as known bugs.

run_testsuite(display_all = true, tests=["rtest1", rtest1a])' will
run tests rtest1' and rtest2', and displays each test.

run_testsuite' changes the Maxima environment.  Typically a test
script executes kill' to establish a known environment (namely
one without user-defined functions and variables) and then defines
functions and variables appropriate to the test.

run_testsuite' returns done'.


Option variable: testsuite_files

     testsuite_files' is the set of tests to be run by
run_testsuite'.  It is a list of names of the files containing
the tests to run.  If some of the tests in a file are known to
fail, then instead of listing the name of the file, a list
containing the file name and the test numbers that fail is used.

For example, this is a part of the default set of tests:

["rtest13s", ["rtest14", 57, 63]]

This specifies the testsuite consists of the files "rtest13s" and
"rtest14", but "rtest14" contains two tests that are known to
fail: 57 and 63.


Function: bug_report ()

     Prints out Maxima and Lisp version numbers, and gives a link to
the Maxima project bug report web page.  The version information
is the same as reported by build_info'.

When a bug is reported, it is helpful to copy the Maxima and Lisp
version information into the bug report.

bug_report' returns an empty string ""'.


Function: build_info ()

     Returns a summary of the parameters of the Maxima build, as a
Maxima structure (defined by defstruct').  The fields of the
structure are: version', timestamp', host', lisp_name', and
lisp_version'.  When the pretty-printer is enabled (via
display2d'), the structure is displayed as a short table.

See also bug_report'.

Examples:

(%i1) build_info ();
(%o1)
Maxima version: "5.26.0_16_gb72c64c_dirty"
Maxima build date: "2012-01-29 12:29:04"
Host type: "i686-pc-linux-gnu"
Lisp implementation type: "CMU Common Lisp"
Lisp implementation version: "CVS release-19a 19a-release-20040728 + minimal debian patches"
(%i2) x : build_info ()$(%i3) x@version; (%o3) 5.26.0_16_gb72c64c_dirty (%i4) x@timestamp; (%o4) 2012-01-29 12:29:04 (%i5) x@host; (%o5) i686-pc-linux-gnu (%i6) x@lisp_name; (%o6) CMU Common Lisp (%i7) x@lisp_version; (%o7) CVS release-19a 19a-release-20040728 + minimal debian patches (%i8) x; (%o8) Maxima version: "5.26.0_16_gb72c64c_dirty" Maxima build date: "2012-01-29 12:29:04" Host type: "i686-pc-linux-gnu" Lisp implementation type: "CMU Common Lisp" Lisp implementation version: "CVS release-19a 19a-release-20040728 + minimal debian patches"  ## 3 Help  Documentation Functions and Variables for Help  ## 3.1 Documentation The Maxima on-line user's manual can be viewed in different forms. From the Maxima interactive prompt, the user's manual is viewed as plain text by the ?' command (i.e., the describe' function). The user's manual is viewed as info' hypertext by the info' viewer program and as a web page by any ordinary web browser. example' displays examples for many Maxima functions. For example, (%i1) example (integrate); yields (%i2) test(f):=block([u],u:integrate(f,x),ratsimp(f-diff(u,x))) (%o2) test(f) := block([u], u : integrate(f, x), ratsimp(f - diff(u, x))) (%i3) test(sin(x)) (%o3) 0 (%i4) test(1/(x+1)) (%o4) 0 (%i5) test(1/(x^2+1)) (%o5) 0 and additional output.  ## 3.2 Functions and Variables for Help Function: apropos (<string>)   Searches for Maxima names which have <string> appearing anywhere within them. Thus, apropos (exp)' returns a list of all the flags and functions which have exp' as part of their names, such as expand', exp', and exponentialize'. Thus if you can only remember part of the name of something you can use this command to find the rest of the name. Similarly, you could say apropos (tr_)' to find a list of many of the switches relating to the translator, most of which begin with tr_'. apropos("")' returns a list with all Maxima names. apropos' returns the empty list []', if no name is found. Example: Show all Maxima symbols which have "gamma"' in the name: (%i1) apropos("gamma"); (%o1) [%gamma, gamma, gammalim, gamma_expand, gamma_greek, gamma_incomplete, gamma_incomplete_generalized, gamma_incomplete_regularized, Gamma, log_gamma, makegamma, prefer_gamma_incomplete, gamma_incomplete_generalized_regularized]  Function: demo (<filename>)   Evaluates Maxima expressions in <filename> and displays the results. demo' pauses after evaluating each expression and continues after the user enters a carriage return. (If running in Xmaxima, demo' may need to see a semicolon ;' followed by a carriage return.) demo' searches the list of directories file_search_demo' to find filename'. If the file has the suffix dem', the suffix may be omitted. See also file_search'. demo' evaluates its argument. demo' returns the name of the demonstration file. Example: (%i1) demo ("disol"); batching /home/wfs/maxima/share/simplification/disol.dem At the _ prompt, type ';' followed by enter to get next demo (%i2) load(disol) _ (%i3) exp1 : a (e (g + f) + b (d + c)) (%o3) a (e (g + f) + b (d + c)) _ (%i4) disolate(exp1, a, b, e) (%t4) d + c (%t5) g + f (%o5) a (%t5 e + %t4 b) _  Function: describe   describe (<string>) describe (<string>, exact) describe (<string>, inexact) describe(<string>)' is equivalent to describe(<string>, exact)'. describe(<string>, exact)' finds an item with title equal (case-insensitive) to <string>, if there is any such item. describe(<string>, inexact)' finds all documented items which contain <string> in their titles. If there is more than one such item, Maxima asks the user to select an item or items to display. At the interactive prompt, ? foo' (with a space between ?' and foo') is equivalent to describe("foo", exact)', and ?? foo' is equivalent to describe("foo", inexact)'. describe("", inexact)' yields a list of all topics documented in the on-line manual. describe' quotes its argument. describe' returns true' if some documentation is found, otherwise false'. See also *note Documentation::. Example: (%i1) ?? integ 0: Functions and Variables for Elliptic Integrals 1: Functions and Variables for Integration 2: Introduction to Elliptic Functions and Integrals 3: Introduction to Integration 4: askinteger (Functions and Variables for Simplification) 5: integerp (Functions and Variables for Miscellaneous Options) 6: integer_partitions (Functions and Variables for Sets) 7: integrate (Functions and Variables for Integration) 8: integrate_use_rootsof (Functions and Variables for Integration) 9: integration_constant_counter (Functions and Variables for Integration) 10: nonnegintegerp (Functions and Variables for linearalgebra) Enter space-separated numbers, all' or none': 7 8 -- Function: integrate (<expr>, <x>) -- Function: integrate (<expr>, <x>, <a>, <b>) Attempts to symbolically compute the integral of <expr> with respect to <x>. integrate (<expr>, <x>)' is an indefinite integral, while integrate (<expr>, <x>, <a>, <b>)' is a definite integral, [...] -- Option variable: integrate_use_rootsof Default value: false' When integrate_use_rootsof' is true' and the denominator of a rational function cannot be factored, integrate' returns the integral in a form which is a sum over the roots (not yet known) of the denominator. [...] In this example, items 7 and 8 were selected (output is shortened as indicated by [...]'). All or none of the items could have been selected by entering all' or none', which can be abbreviated a' or n', respectively.  Function: example   example (<topic>) example () example (<topic>)' displays some examples of <topic>, which is a symbol or a string. To get examples for operators like if', do', or lambda' the argument must be a string, e.g. example ("do")'. example' is not case sensitive. Most topics are function names. example ()' returns the list of all recognized topics. The name of the file containing the examples is given by the global option variable manual_demo', which defaults to "manual.demo"'. example' quotes its argument. example' returns done' unless no examples are found or there is no argument, in which case example' returns the list of all recognized topics. Examples: (%i1) example(append); (%i2) append([x+y,0,-3.2],[2.5e+20,x]) (%o2) [y + x, 0, - 3.2, 2.5e+20, x] (%o2) done (%i3) example("lambda"); (%i4) lambda([x,y,z],z^2+y^2+x^2) 2 2 2 (%o4) lambda([x, y, z], z + y + x ) (%i5) %(1,2,a) 2 (%o5) a + 5 (%i6) a+2+1 (%o6) a + 3 (%o6) done  Option variable: manual_demo   Default value: "manual.demo"' manual_demo' specifies the name of the file containing the examples for the function example'. See example'.  ## 4 Command Line  Introduction to Command Line Functions and Variables for Command Line Functions and Variables for Display  ## 4.1 Introduction to Command Line ## 4.2 Functions and Variables for Command Line System variable: __   __' is the input expression currently being evaluated. That is, while an input expression <expr> is being evaluated, __' is <expr>. __' is assigned the input expression before the input is simplified or evaluated. However, the value of __' is simplified (but not evaluated) when it is displayed. __' is recognized by batch' and load'. In a file processed by batch', __' has the same meaning as at the interactive prompt. In a file processed by load', __' is bound to the input expression most recently entered at the interactive prompt or in a batch file; __' is not bound to the input expressions in the file being processed. In particular, when load (<filename>)' is called from the interactive prompt, __' is bound to load (<filename>)' while the file is being processed. See also _' and %'. Examples: (%i1) print ("I was called as", __); I was called as print(I was called as, __) (%o1) print(I was called as, __) (%i2) foo (__); (%o2) foo(foo(__)) (%i3) g (x) := (print ("Current input expression =", __), 0); (%o3) g(x) := (print("Current input expression =", __), 0) (%i4) [aa : 1, bb : 2, cc : 3]; (%o4) [1, 2, 3] (%i5) (aa + bb + cc)/(dd + ee + g(x)); cc + bb + aa Current input expression = -------------- g(x) + ee + dd 6 (%o5) ------- ee + dd  System variable: _   _' is the most recent input expression (e.g., %i1', %i2', %i3', ...). _' is assigned the input expression before the input is simplified or evaluated. However, the value of _' is simplified (but not evaluated) when it is displayed. _' is recognized by batch' and load'. In a file processed by batch', _' has the same meaning as at the interactive prompt. In a file processed by load', _' is bound to the input expression most recently evaluated at the interactive prompt or in a batch file; _' is not bound to the input expressions in the file being processed. See also __' and %'. Examples: (%i1) 13 + 29; (%o1) 42 (%i2) :lisp$_
((MPLUS) 13 29)
(%i2) _;
(%o2)                          42
(%i3) sin (%pi/2);
(%o3)                           1
(%i4) :lisp $_ ((%SIN) ((MQUOTIENT)$%PI 2))
(%i4) _;
(%o4)                           1
(%i5) a: 13$(%i6) b: 29$
(%i7) a + b;
(%o7)                          42
(%i8) :lisp $_ ((MPLUS)$A $B) (%i8) _; (%o8) b + a (%i9) a + b; (%o9) 42 (%i10) ev (_); (%o10) 42  System variable: %   %' is the output expression (e.g., %o1', %o2', %o3', ...) most recently computed by Maxima, whether or not it was displayed. %' is recognized by batch' and load'. In a file processed by batch', %' has the same meaning as at the interactive prompt. In a file processed by load', %' is bound to the output expression most recently computed at the interactive prompt or in a batch file; %' is not bound to output expressions in the file being processed. See also _', %%', and %th'.  System variable: %%   In compound statements, namely block', lambda', or (<s_1>, ..., <s_n>)', %%' is the value of the previous statement. At the first statement in a compound statement, or outside of a compound statement, %%' is undefined. %%' is recognized by batch' and load', and it has the same meaning as at the interactive prompt. See also %'. Examples: The following two examples yield the same result. (%i1) block (integrate (x^5, x), ev (%%, x=2) - ev (%%, x=1)); 21 (%o1) -- 2 (%i2) block ([prev], prev: integrate (x^5, x), ev (prev, x=2) - ev (prev, x=1)); 21 (%o2) -- 2 A compound statement may comprise other compound statements. Whether a statement be simple or compound, %%' is the value of the previous statement. (%i3) block (block (a^n, %%*42), %%/6); n (%o3) 7 a Within a compound statement, the value of %%' may be inspected at a break prompt, which is opened by executing the break' function. For example, entering %%;' in the following example yields 42'. (%i4) block (a: 42, break ())$

Entering a Maxima break point. Type 'exit;' to resume.
_%%;
42
_


Function: %th (<i>)

     The value of the <i>'th previous output expression.  That is, if
the next expression to be computed is the <n>'th output, %th
(<m>)' is the (<n> - <m>)'th output.

%th' is recognized by batch' and load'.  In a file processed by
batch', %th' has the same meaning as at the interactive prompt.
In a file processed by load', %th' refers to output expressions
most recently computed at the interactive prompt or in a batch
file; %th' does not refer to output expressions in the file being
processed.

See also %' and %%'.

Example:

%th' is useful in batch' files or for referring to a group of
output expressions.  This example sets s' to the sum of the last
five output expressions.

(%i1) 1;2;3;4;5;
(%o1)                           1
(%o2)                           2
(%o3)                           3
(%o4)                           4
(%o5)                           5
(%i6) block (s: 0, for i:1 thru 5 do s: s + %th(i), s);
(%o6)                          15


Special symbol: ?

     As prefix to a function or variable name, ?' signifies that the
name is a Lisp name, not a Maxima name.  For example, ?round'
signifies the Lisp function ROUND'.  See *note Lisp and Maxima::
for more on this point.

The notation ? word' (a question mark followed a word, separated
by whitespace) is equivalent to describe("word")'.  The question
mark must occur at the beginning of an input line; otherwise it is
describe'.


Special symbol: ??

     The notation ?? word' (??' followed a word, separated by
whitespace) is equivalent to describe("word", inexact)'.  The
question mark must occur at the beginning of an input line;
otherwise it is not recognized as a request for documentation.


Input terminator: $  The dollar sign $' terminates an input expression, and the most
recent output %' and an output label, e.g. %o1', are assigned
the result, but the result is not displayed.

Example:
(%i1) 1 + 2 + 3 $(%i2) %; (%o2) 6 (%i3) %o1; (%o3) 6  Input terminator: ;   The semicolon ;' terminates an input expression, and the resulting output is displayed. See also $'.

Example:
(%i1) 1 + 2 + 3;
(%o1)                           6


Option variable: inchar

     Default value: %i'

inchar' is the prefix of the labels of expressions entered by the
user.  Maxima automatically constructs a label for each input
expression by concatenating inchar' and linenum'.

inchar' may be assigned any string or symbol, not necessarily a
single character.  Because Maxima internally takes into account
only the first char of the prefix, the prefixes inchar',
outchar', and linechar' should have a different first char.
Otherwise some commands like kill(inlables)' do not work as
expected.

Example:

(%i1) inchar: "input";
(%o1)                         input
(input2) expand((a+b)^3);
3        2      2      3
(%o2)               b  + 3 a b  + 3 a  b + a
(input3)


System variable: infolists

     Default value: []'

infolists' is a list of the names of all of the information lists
in Maxima.  These are:

labels'
All bound %i', %o', and %t' labels.

values'
All bound atoms which are user variables, not Maxima options
or switches, created by :' or ::' or functional binding.

functions'
All user-defined functions, created by :=' or define'.

arrays'
All declared and undeclared arrays, created by :', ::', or
:='.

macros'
All user-defined macro functions, created by ::='.

myoptions'
All options ever reset by the user (whether or not they are
later reset to their default values).

rules'
All user-defined pattern matching and simplification rules,
created by tellsimp', tellsimpafter', defmatch', or
defrule'.

aliases'
All atoms which have a user-defined alias, created by the
alias', ordergreat', orderless' functions or by declaring
the atom as a noun' with declare'.

dependencies'
All atoms which have functional dependencies, created by the
depends', dependencies', or gradef' functions.

gradefs'
All functions which have user-defined derivatives, created by

props'
All atoms which have any property other than those mentioned
above, such as properties established by atvalue' or
matchdeclare', etc., as well as properties established in
the declare' function.

let_rule_packages'
All user-defined let' rule packages plus the special package
default_let_rule_package'.  (default_let_rule_package' is
the name of the rule package used when one is not explicitly
set by the user.)


Function: kill

          kill (<a_1>, ..., <a_n>)
kill (labels)
kill (inlabels, outlabels, linelabels)
kill (<n>)
kill ([<m>, <n>])
kill (values, functions, arrays, ...)
kill (all)
kill (allbut (<a_1>, ..., <a_n>))
Removes all bindings (value, function, array, or rule) from the
arguments <a_1>, ..., <a_n>.  An argument <a_k> may be a symbol or
a single array element.  When <a_k> is a single array element,
kill' unbinds that element without affecting any other elements
of the array.

Several special arguments are recognized.  Different kinds of
arguments may be combined, e.g., kill (inlabels, functions,
allbut (foo, bar))'.

kill (labels)' unbinds all input, output, and intermediate
expression labels created so far.  kill (inlabels)' unbinds only
input labels which begin with the current value of inchar'.
Likewise, kill (outlabels)' unbinds only output labels which
begin with the current value of outchar', and kill (linelabels)'
unbinds only intermediate expression labels which begin with the
current value of linechar'.

kill (<n>)', where <n> is an integer, unbinds the <n> most recent
input and output labels.

kill ([<m>, <n>])' unbinds input and output labels <m> through
<n>.

kill (<infolist>)', where <infolist> is any item in infolists'
(such as values', functions', or arrays') unbinds all items in
<infolist>.  See also infolists'.

kill (all)' unbinds all items on all infolists.  kill (all)' does
not reset global variables to their default values; see reset' on
this point.

kill (allbut (<a_1>, ..., <a_n>))' unbinds all items on all
infolists except for <a_1>, ..., <a_n>.  kill (allbut
(<infolist>))' unbinds all items except for the ones on
<infolist>, where <infolist> is values', functions', arrays',
etc.

The memory taken up by a bound property is not released until all
symbols are unbound from it.  In particular, to release the memory
taken up by the value of a symbol, one unbinds the output label
which shows the bound value, as well as unbinding the symbol
itself.

kill' quotes its arguments.  The quote-quote operator '''
defeats quotation.

kill (<symbol>)' unbinds all properties of <symbol>.  In contrast,
the functions remvalue', remfunction', remarray', and remrule'
unbind a specific property.

kill' always returns done', even if an argument has no binding.


Function: labels (<symbol>)

     Returns the list of input, output, or intermediate expression
labels which begin with <symbol>.  Typically <symbol> is the value
of inchar', outchar', or linechar'.  If no labels begin with
<symbol>, labels' returns an empty list.

By default, Maxima displays the result of each user input
expression, giving the result an output label.  The output display
is suppressed by terminating the input with $' (dollar sign) instead of ;' (semicolon). An output label is constructed and bound to the result, but not displayed, and the label may be referenced in the same way as displayed output labels. See also %', %%', and %th'. Intermediate expression labels can be generated by some functions. The option variable programmode' controls whether solve' and some other functions generate intermediate expression labels instead of returning a list of expressions. Some other functions, such as ldisplay', always generate intermediate expression labels. See also inchar', outchar', linechar', and infolists'.  System variable: labels   The variable labels' is the list of input, output, and intermediate expression labels, including all previous labels if inchar', outchar', or linechar' were redefined.  Option variable: linechar   Default value: %t' linechar' is the prefix of the labels of intermediate expressions generated by Maxima. Maxima constructs a label for each intermediate expression (if displayed) by concatenating linechar' and linenum'. linechar' may be assigned any string or symbol, not necessarily a single character. Because Maxima internally takes into account only the first char of the prefix, the prefixes inchar', outchar', and linechar' should have a different first char. Otherwise some commands like kill(inlables)' do not work as expected. Intermediate expressions might or might not be displayed. See programmode' and labels'.  System variable: linenum   The line number of the current pair of input and output expressions.  System variable: myoptions   Default value: []' myoptions' is the list of all options ever reset by the user, whether or not they get reset to their default value.  Option variable: nolabels   Default value: false' When nolabels' is true', input and output result labels (%i' and %o', respectively) are displayed, but the labels are not bound to results, and the labels are not appended to the labels' list. Since labels are not bound to results, garbage collection can recover the memory taken up by the results. Otherwise input and output result labels are bound to results, and the labels are appended to the labels' list. Intermediate expression labels (%t') are not affected by nolabels'; whether nolabels' is true' or false', intermediate expression labels are bound and appended to the labels' list. See also batch', load', and labels'.  Option variable: optionset   Default value: false' When optionset' is true', Maxima prints out a message whenever a Maxima option is reset. This is useful if the user is doubtful of the spelling of some option and wants to make sure that the variable he assigned a value to was truly an option variable. Example: (%i1) optionset:true; assignment: assigning to option optionset (%o1) true (%i2) gamma_expand:true; assignment: assigning to option gamma_expand (%o2) true  Option variable: outchar   Default value: %o' outchar' is the prefix of the labels of expressions computed by Maxima. Maxima automatically constructs a label for each computed expression by concatenating outchar' and linenum'. outchar' may be assigned any string or symbol, not necessarily a single character. Because Maxima internally takes into account only the first char of the prefix, the prefixes inchar', outchar' and linechar' should have a different first char. Otherwise some commands like kill(inlables)' do not work as expected. See also labels'. Example: (%i1) outchar: "output"; (output1) output (%i2) expand((a+b)^3); 3 2 2 3 (output2) b + 3 a b + 3 a b + a (%i3)  Function: playback   playback () playback (<n>) playback ([<m>, <n>]) playback ([<m>]) playback (input) playback (slow) playback (time) playback (grind) Displays input, output, and intermediate expressions, without recomputing them. playback' only displays the expressions bound to labels; any other output (such as text printed by print' or describe', or error messages) is not displayed. See also labels'. playback' quotes its arguments. The quote-quote operator ''' defeats quotation. playback' always returns done'. playback ()' (with no arguments) displays all input, output, and intermediate expressions generated so far. An output expression is displayed even if it was suppressed by the $' terminator when
it was originally computed.

playback (<n>)' displays the most recent <n> expressions.  Each
input, output, and intermediate expression counts as one.

playback ([<m>, <n>])' displays input, output, and intermediate
expressions with numbers from <m> through <n>, inclusive.

playback ([<m>])' is equivalent to playback ([<m>, <m>])'; this
usually prints one pair of input and output expressions.

playback (input)' displays all input expressions generated so far.

playback (slow)' pauses between expressions and waits for the
user to press enter'.  This behavior is similar to demo'.
playback (slow)' is useful in conjunction with save' or
stringout' when creating a secondary-storage file in order to
pick out useful expressions.

playback (time)' displays the computation time for each
expression.

playback (grind)' displays input expressions in the same format
as the grind' function.  Output expressions are not affected by
the grind' option.  See grind'.

Arguments may be combined, e.g., playback ([5, 10], grind, time,
slow)'.


Option variable: prompt

     Default value: _'

prompt' is the prompt symbol of the demo' function, playback
(slow)' mode, and the Maxima break loop (as invoked by break').


Function: quit ()

     Terminates the Maxima session.  Note that the function must be
invoked as quit();' or quit()$', not quit' by itself. To stop a lengthy computation, type control-C'. The default action is to return to the Maxima prompt. If *debugger-hook*' is nil', control-C' opens the Lisp debugger. See also *note Debugging::.  Function: read (<expr_1>, ..., <expr_n>)   Prints <expr_1>, ..., <expr_n>, then reads one expression from the console and returns the evaluated expression. The expression is terminated with a semicolon ;' or dollar sign $'.

Example:

(%i1) foo: 42$(%i2) foo: read ("foo is", foo, " -- enter new value.")$
foo is 42  -- enter new value.
(a+b)^3;
(%i3) foo;
3
(%o3)                         (b + a)


Function: readonly (<expr_1>, ..., <expr_n>)

     Prints <expr_1>, ..., <expr_n>, then reads one expression from the
console and returns the expression (without evaluation).  The
expression is terminated with a ;' (semicolon) or $' (dollar sign). See also read'. Examples: (%i1) aa: 7$
(%i2) foo: readonly ("Enter an expression:");
Enter an expression:
2^aa;
aa
(%o2)                            2
(%i3) foo: read ("Enter an expression:");
Enter an expression:
2^aa;
(%o3)                            128


Function: reset ()

     Resets many global variables and options, and some other
variables, to their default values.

reset' processes the variables on the Lisp list
*variable-initial-values*'.  The Lisp macro defmvar' puts
variables on this list (among other actions).  Many, but not all,
global variables and options are defined by defmvar', and some
variables defined by defmvar' are not global variables or options.


Option variable: showtime

     Default value: false'

When showtime' is true', the computation time and elapsed time is
printed with each output expression.

The computation time is always recorded, so time' and playback'
can display the computation time even when showtime' is false'.


Function: to_lisp ()

     Enters the Lisp system under Maxima.  (to-maxima)' returns to
Maxima.

Example:

Define a function and enter the Lisp system under Maxima.  The
definition is inspected on the property list, then the function
definition is extracted, factored and stored in the variable
$result. The variable can be used in Maxima after returning to Maxima. (%i1) f(x):=x^2+x; 2 (%o1) f(x) := x + x (%i2) to_lisp(); Type (to-maxima) to restart, ($quit) to quit Maxima.
MAXIMA> (symbol-plist '$f) (MPROPS (NIL MEXPR ((LAMBDA) ((MLIST)$X)
((MPLUS) ((MEXPT) $X 2)$X))))
MAXIMA> (setq $result ($factor (caddr (mget '$f 'mexpr)))) ((MTIMES SIMP FACTORED)$X ((MPLUS SIMP IRREDUCIBLE) 1 $X)) MAXIMA> (to-maxima) Returning to Maxima (%o2) true (%i3) result; (%o3) x (x + 1)  System variable: values   Initial value: []' values' is a list of all bound user variables (not Maxima options or switches). The list comprises symbols bound by :', or ::'. If the value of a variable is removed with the commands kill', remove', or remvalue' the variable is deleted from values'. See functions' for a list of user defined functions. Examples: First, values' shows the symbols a', b', and c', but not d', it is not bound to a value, and not the user function f'. The values are removed from the variables. values' is the empty list. (%i1) [a:99, b::a-90, c:a-b, d, f(x):= x^2]; 2 (%o1) [99, 9, 90, d, f(x) := x ] (%i2) values; (%o2) [a, b, c] (%i3) [kill(a), remove(b,value), remvalue(c)]; (%o3) [done, done, [c]] (%i4) values; (%o4) []  ## 4.3 Functions and Variables for Display Option variable: %edispflag   Default value: false' When %edispflag' is true', Maxima displays %e' to a negative exponent as a quotient. For example, %e^-x' is displayed as 1/%e^x'. See also exptdispflag'. Example: (%i1) %e^-10; - 10 (%o1) %e (%i2) %edispflag:true$
(%i3) %e^-10;
1
(%o3)                         ----
10
%e


Option variable: absboxchar

     Default value: !'

absboxchar' is the character used to draw absolute value signs
around expressions which are more than one line tall.

Example:

(%i1) abs((x^3+1));
! 3    !
(%o1)                       !x  + 1!


Function: disp (<expr_1>, <expr_2>, ...)

     is like display' but only the value of the arguments are
displayed rather than equations.  This is useful for complicated
arguments which don't have names or where only the value of the
argument is of interest and not the name.

See also ldisp' and print'.

Example:

(%i1) b[1,2]:x-x^2$(%i2) x:123$
(%i3) disp(x, b[1,2], sin(1.0));
123

2
x - x

.8414709848078965

(%o3)                         done


Function: display (<expr_1>, <expr_2>, ...)

     Displays equations whose left side is <expr_i> unevaluated, and
whose right side is the value of the expression centered on the
line.  This function is useful in blocks and for' statements in
order to have intermediate results displayed.  The arguments to
display' are usually atoms, subscripted variables, or function
calls.

See also ldisplay', disp', and ldisp'.

Example:

(%i1) b[1,2]:x-x^2$(%i2) x:123$
(%i3) display(x, b[1,2], sin(1.0));
x = 123

2
b     = x - x
1, 2

sin(1.0) = .8414709848078965

(%o3)                         done


Option variable: display2d

     Default value: true'

When display2d' is false', the console display is a string
(1-dimensional) form rather than a display (2-dimensional) form.

centered display of equations.

Example:

(%i1) x/(x^2+1);
x
(%o1)                        ------
2
x  + 1
(%i2) display2d:false$(%i3) x/(x^2+1); (%o3) x/(x^2+1)  Option variable: display_format_internal   Default value: false' When display_format_internal' is true', expressions are displayed without being transformed in ways that hide the internal mathematical representation. The display then corresponds to what inpart' returns rather than part'. Examples: User part inpart a-b; a - b a + (- 1) b a - 1 a/b; - a b b 1/2 sqrt(x); sqrt(x) x 4 X 4 X*4/3; --- - X 3 3  Function: dispterms (<expr>)   Displays <expr> in parts one below the other. That is, first the operator of <expr> is displayed, then each term in a sum, or factor in a product, or part of a more general expression is displayed separately. This is useful if <expr> is too large to be otherwise displayed. For example if P1', P2', ... are very large expressions then the display program may run out of storage space in trying to display P1 + P2 + ...' all at once. However, dispterms (P1 + P2 + ...)' displays P1', then below it P2', etc. When not using dispterms', if an exponential expression is too wide to be displayed as A^B' it appears as expt (A, B)' (or as ncexpt (A, B)' in the case of A^^B'). Example: (%i1) dispterms(2*a*sin(x)+%e^x); + 2 a sin(x) x %e (%o1) done  Special symbol: expt (<a>, <b>)  Special symbol: ncexpt (<a>, <b>)   If an exponential expression is too wide to be displayed as <a>^<b>' it appears as expt (<a>, <b>)' (or as ncexpt (<a>, <b>)' in the case of <a>^^<b>'). expt' and ncexpt' are not recognized in input.  Option variable: exptdispflag   Default value: true' When exptdispflag' is true', Maxima displays expressions with negative exponents using quotients. See also %edispflag'. Example: (%i1) exptdispflag:true; (%o1) true (%i2) 10^-x; 1 (%o2) --- x 10 (%i3) exptdispflag:false; (%o3) false (%i4) 10^-x; - x (%o4) 10  Function: grind (<expr>)   The function grind' prints <expr> to the console in a form suitable for input to Maxima. grind' always returns done'. When <expr> is the name of a function or macro, grind' prints the function or macro definition instead of just the name. See also string', which returns a string instead of printing its output. grind' attempts to print the expression in a manner which makes it slightly easier to read than the output of string'. grind' evaluates its argument. Examples: (%i1) aa + 1729; (%o1) aa + 1729 (%i2) grind (%); aa+1729$
(%o2)                         done
(%i3) [aa, 1729, aa + 1729];
(%o3)                 [aa, 1729, aa + 1729]
(%i4) grind (%);
[aa,1729,aa+1729]$(%o4) done (%i5) matrix ([aa, 17], [29, bb]); [ aa 17 ] (%o5) [ ] [ 29 bb ] (%i6) grind (%); matrix([aa,17],[29,bb])$
(%o6)                         done
(%i7) set (aa, 17, 29, bb);
(%o7)                   {17, 29, aa, bb}
(%i8) grind (%);
{17,29,aa,bb}$(%o8) done (%i9) exp (aa / (bb + 17)^29); aa ----------- 29 (bb + 17) (%o9) %e (%i10) grind (%); %e^(aa/(bb+17)^29)$
(%o10)                        done
(%i11) expr: expand ((aa + bb)^10);
10           9        2   8         3   7         4   6
(%o11) bb   + 10 aa bb  + 45 aa  bb  + 120 aa  bb  + 210 aa  bb
5   5         6   4         7   3        8   2
+ 252 aa  bb  + 210 aa  bb  + 120 aa  bb  + 45 aa  bb
9        10
+ 10 aa  bb + aa
(%i12) grind (expr);
bb^10+10*aa*bb^9+45*aa^2*bb^8+120*aa^3*bb^7+210*aa^4*bb^6
+252*aa^5*bb^5+210*aa^6*bb^4+120*aa^7*bb^3+45*aa^8*bb^2
+10*aa^9*bb+aa^10$(%o12) done (%i13) string (expr); (%o13) bb^10+10*aa*bb^9+45*aa^2*bb^8+120*aa^3*bb^7+210*aa^4*bb^6\ +252*aa^5*bb^5+210*aa^6*bb^4+120*aa^7*bb^3+45*aa^8*bb^2+10*aa^9*\ bb+aa^10 (%i14) cholesky (A):= block ([n : length (A), L : copymatrix (A), p : makelist (0, i, 1, length (A))], for i thru n do for j : i thru n do (x : L[i, j], x : x - sum (L[j, k] * L[i, k], k, 1, i - 1), if i = j then p[i] : 1 / sqrt(x) else L[j, i] : x * p[i]), for i thru n do L[i, i] : 1 / p[i], for i thru n do for j : i + 1 thru n do L[i, j] : 0, L)$
(%i15) grind (cholesky);
cholesky(A):=block(
[n:length(A),L:copymatrix(A),
p:makelist(0,i,1,length(A))],
for i thru n do
(for j from i thru n do
(x:L[i,j],x:x-sum(L[j,k]*L[i,k],k,1,i-1),
if i = j then p[i]:1/sqrt(x)
else L[j,i]:x*p[i])),
for i thru n do L[i,i]:1/p[i],
for i thru n do (for j from i+1 thru n do L[i,j]:0),L)$(%o15) done (%i16) string (fundef (cholesky)); (%o16) cholesky(A):=block([n:length(A),L:copymatrix(A),p:makelis\ t(0,i,1,length(A))],for i thru n do (for j from i thru n do (x:L\ [i,j],x:x-sum(L[j,k]*L[i,k],k,1,i-1),if i = j then p[i]:1/sqrt(x\ ) else L[j,i]:x*p[i])),for i thru n do L[i,i]:1/p[i],for i thru \ n do (for j from i+1 thru n do L[i,j]:0),L)  Option variable: grind   When the variable grind' is true', the output of string' and stringout' has the same format as that of grind'; otherwise no attempt is made to specially format the output of those functions. The default value of the variable grind' is false'. grind' can also be specified as an argument of playback'. When grind' is present, playback' prints input expressions in the same format as the grind' function. Otherwise, no attempt is made to specially format input expressions.  Option variable: ibase   Default value: 10' ibase' is the base for integers read by Maxima. ibase' may be assigned any integer between 2 and 36 (decimal), inclusive. When ibase' is greater than 10, the numerals comprise the decimal numerals 0 through 9 plus letters of the alphabet A, B, C, ..., as needed to make ibase' digits in all. Letters are interpreted as digits only if the first digit is 0 through 9. Uppercase and lowercase letters are not distinguished. The numerals for base 36, the largest acceptable base, comprise 0 through 9 and A through Z. Whatever the value of ibase', when an integer is terminated by a decimal point, it is interpreted in base 10. See also obase'. Examples: ibase' less than 10. (%i1) ibase : 2$
(%i2) obase;
(%o2)                          10
(%i3) 1111111111111111;
(%o3)                         65535

ibase' greater than 10.  Letters are interpreted as digits only
if the first digit is 0 through 9.

(%i1) ibase : 16 $(%i2) obase; (%o2) 10 (%i3) 1000; (%o3) 4096 (%i4) abcd; (%o4) abcd (%i5) symbolp (abcd); (%o5) true (%i6) 0abcd; (%o6) 43981 (%i7) symbolp (0abcd); (%o7) false When an integer is terminated by a decimal point, it is interpreted in base 10. (%i1) ibase : 36$
(%i2) obase;
(%o2)                          10
(%i3) 1234;
(%o3)                         49360
(%i4) 1234.;
(%o4)                         1234


Function: ldisp (<expr_1>, ..., <expr_n>)

     Displays expressions <expr_1>, ..., <expr_n> to the console as
printed output.  ldisp' assigns an intermediate expression label
to each argument and returns the list of labels.

See also disp', display', and ldisplay'.

Examples:

(%i1) e: (a+b)^3;
3
(%o1)                       (b + a)
(%i2) f: expand (e);
3        2      2      3
(%o2)               b  + 3 a b  + 3 a  b + a
(%i3) ldisp (e, f);
3
(%t3)                       (b + a)

3        2      2      3
(%t4)               b  + 3 a b  + 3 a  b + a

(%o4)                      [%t3, %t4]
(%i4) %t3;
3
(%o4)                       (b + a)
(%i5) %t4;
3        2      2      3
(%o5)               b  + 3 a b  + 3 a  b + a


Function: ldisplay (<expr_1>, ..., <expr_n>)

     Displays expressions <expr_1>, ..., <expr_n> to the console as
printed output.  Each expression is printed as an equation of the
form lhs = rhs' in which lhs' is one of the arguments of
ldisplay' and rhs' is its value.  Typically each argument is a
variable.  ldisp' assigns an intermediate expression label to
each equation and returns the list of labels.

See also display', disp', and ldisp'.

Examples:

(%i1) e: (a+b)^3;
3
(%o1)                       (b + a)
(%i2) f: expand (e);
3        2      2      3
(%o2)               b  + 3 a b  + 3 a  b + a
(%i3) ldisplay (e, f);
3
(%t3)                     e = (b + a)

3        2      2      3
(%t4)             f = b  + 3 a b  + 3 a  b + a

(%o4)                      [%t3, %t4]
(%i4) %t3;
3
(%o4)                     e = (b + a)
(%i5) %t4;
3        2      2      3
(%o5)             f = b  + 3 a b  + 3 a  b + a


Option variable: leftjust

     Default value: false'

When leftjust' is true', equations in 2D-display are drawn left
justified rather than centered.

See also display2d' to switch between 1D- and 2D-display.

Example:

(%i1) expand((x+1)^3);
3      2
(%o1)                  x  + 3 x  + 3 x + 1
(%i2) leftjust:true$(%i3) expand((x+1)^3); 3 2 (%o3) x + 3 x + 3 x + 1  Option variable: linel   Default value: 79' linel' is the assumed width (in characters) of the console display for the purpose of displaying expressions. linel' may be assigned any value by the user, although very small or very large values may be impractical. Text printed by built-in Maxima functions, such as error messages and the output of describe', is not affected by linel'.  Option variable: lispdisp   Default value: false' When lispdisp' is true', Lisp symbols are displayed with a leading question mark ?'. Otherwise, Lisp symbols are displayed with no leading mark. This has the same effect for 1-d and 2-d display. Examples: (%i1) lispdisp: false$
(%i2) ?foo + ?bar;
(%o2)                       foo + bar
(%i3) lispdisp: true$(%i4) ?foo + ?bar; (%o4) ?foo + ?bar  Option variable: negsumdispflag   Default value: true' When negsumdispflag' is true', x - y' displays as x - y' instead of as - y + x'. Setting it to false' causes the special check in display for the difference of two expressions to not be done. One application is that thus a + %i*b' and a - %i*b' may both be displayed the same way.  Option variable: obase   Default value: 10' obase' is the base for integers displayed by Maxima. obase' may be assigned any integer between 2 and 36 (decimal), inclusive. When obase' is greater than 10, the numerals comprise the decimal numerals 0 through 9 plus capital letters of the alphabet A, B, C, ..., as needed. A leading 0 digit is displayed if the leading digit is otherwise a letter. The numerals for base 36, the largest acceptable base, comprise 0 through 9, and A through Z. See also ibase'. Examples: (%i1) obase : 2; (%o1) 10 (%i2) 2^8 - 1; (%o10) 11111111 (%i3) obase : 8; (%o3) 10 (%i4) 8^8 - 1; (%o4) 77777777 (%i5) obase : 16; (%o5) 10 (%i6) 16^8 - 1; (%o6) 0FFFFFFFF (%i7) obase : 36; (%o7) 10 (%i8) 36^8 - 1; (%o8) 0ZZZZZZZZ  Option variable: pfeformat   Default value: false' When pfeformat' is true', a ratio of integers is displayed with the solidus (forward slash) character, and an integer denominator n' is displayed as a leading multiplicative term 1/n'. Examples: (%i1) pfeformat: false$
(%i2) 2^16/7^3;
65536
(%o2)                         -----
343
(%i3) (a+b)/8;
b + a
(%o3)                         -----
8
(%i4) pfeformat: true$(%i5) 2^16/7^3; (%o5) 65536/343 (%i6) (a+b)/8; (%o6) 1/8 (b + a)  Option variable: powerdisp   Default value: false' When powerdisp' is true', a sum is displayed with its terms in order of increasing power. Thus a polynomial is displayed as a truncated power series, with the constant term first and the highest power last. By default, terms of a sum are displayed in order of decreasing power. Example: (%i1) powerdisp:true; (%o1) true (%i2) x^2+x^3+x^4; 2 3 4 (%o2) x + x + x (%i3) powerdisp:false; (%o3) false (%i4) x^2+x^3+x^4; 4 3 2 (%o4) x + x + x  Function: print (<expr_1>, ..., <expr_n>)   Evaluates and displays <expr_1>, ..., <expr_n> one after another, from left to right, starting at the left edge of the console display. The value returned by print' is the value of its last argument. print' does not generate intermediate expression labels. See also display', disp', ldisplay', and ldisp'. Those functions display one expression per line, while print' attempts to display two or more expressions per line. To display the contents of a file, see printfile'. Examples: (%i1) r: print ("(a+b)^3 is", expand ((a+b)^3), "log (a^10/b) is", radcan (log (a^10/b)))$
3        2      2      3
(a+b)^3 is b  + 3 a b  + 3 a  b + a  log (a^10/b) is

10 log(a) - log(b)
(%i2) r;
(%o2)                  10 log(a) - log(b)
(%i3) disp ("(a+b)^3 is", expand ((a+b)^3), "log (a^10/b) is",
radcan (log (a^10/b)))$(a+b)^3 is 3 2 2 3 b + 3 a b + 3 a b + a log (a^10/b) is 10 log(a) - log(b)  Option variable: sqrtdispflag   Default value: true' When sqrtdispflag' is false', causes sqrt' to display with exponent 1/2.  Option variable: stardisp   Default value: false' When stardisp' is true', multiplication is displayed with an asterisk *' between operands.  Option variable: ttyoff   Default value: false' When ttyoff' is true', output expressions are not displayed. Output expressions are still computed and assigned labels. See labels'. Text printed by built-in Maxima functions, such as error messages and the output of describe', is not affected by ttyoff'.  ## 5 Data Types and Structures  Numbers Strings Constants Lists Arrays Structures  ## 5.1 Numbers  * Introduction to Numbers:: * Functions and Variables for Numbers::  Function: bfloat (<expr>)   Converts all numbers and functions of numbers in <expr> to bigfloat numbers. The number of significant digits in the resulting bigfloats is specified by the global variable fpprec'. When float2bf' is false' a warning message is printed when a floating point number is converted into a bigfloat number (since this may lead to loss of precision).  Function: bfloatp (<expr>)   Returns true' if <expr> is a bigfloat number, otherwise false'.  Option variable: bftorat   Default value: false' bftorat' controls the conversion of bfloats to rational numbers. When bftorat' is false', ratepsilon' will be used to control the conversion (this results in relatively small rational numbers). When bftorat' is true', the rational number generated will accurately represent the bfloat. Note: bftorat' has no effect on the transformation to rational numbers with the function rationalize'. Example: (%i1) ratepsilon:1e-4; (%o1) 1.e-4 (%i2) rat(bfloat(11111/111111)), bftorat:false; rat' replaced 9.99990999991B-2 by 1/10 = 1.0B-1 1 (%o2)/R/ -- 10 (%i3) rat(bfloat(11111/111111)), bftorat:true; rat' replaced 9.99990999991B-2 by 11111/111111 = 9.99990999991B-2 11111 (%o3)/R/ ------ 111111  Option variable: bftrunc   Default value: true' bftrunc' causes trailing zeroes in non-zero bigfloat numbers not to be displayed. Thus, if bftrunc' is false', bfloat (1)' displays as 1.000000000000000B0'. Otherwise, this is displayed as 1.0B0'.  Function: evenp (<expr>)   Returns true' if <expr> is an even integer. false' is returned in all other cases.  Function: float (<expr>)   Converts integers, rational numbers and bigfloats in <expr> to floating point numbers. It is also an evflag', float' causes non-integral rational numbers and bigfloat numbers to be converted to floating point.  Option variable: float2bf   Default value: true' When float2bf' is false', a warning message is printed when a floating point number is converted into a bigfloat number (since this may lead to loss of precision).  Function: floatnump (<expr>)   Returns true' if <expr> is a floating point number, otherwise false'.  Option variable: fpprec   Default value: 16 fpprec' is the number of significant digits for arithmetic on bigfloat numbers. fpprec' does not affect computations on ordinary floating point numbers. See also bfloat' and fpprintprec'.  Option variable: fpprintprec   Default value: 0 fpprintprec' is the number of digits to print when printing an ordinary float or bigfloat number. For ordinary floating point numbers, when fpprintprec' has a value between 2 and 16 (inclusive), the number of digits printed is equal to fpprintprec'. Otherwise, fpprintprec' is 0, or greater than 16, and the number of digits printed is 16. For bigfloat numbers, when fpprintprec' has a value between 2 and fpprec' (inclusive), the number of digits printed is equal to fpprintprec'. Otherwise, fpprintprec' is 0, or greater than fpprec', and the number of digits printed is equal to fpprec'. For both ordinary floats and bigfloats, trailing zero digits are suppressed. The actual number of digits printed is less than fpprintprec' if there are trailing zero digits. fpprintprec' cannot be 1.  Function: integerp (<expr>)   Returns true' if <expr> is a literal numeric integer, otherwise false'. integerp' returns false' if its argument is a symbol, even if the argument is declared integer. Examples: (%i1) integerp (0); (%o1) true (%i2) integerp (1); (%o2) true (%i3) integerp (-17); (%o3) true (%i4) integerp (0.0); (%o4) false (%i5) integerp (1.0); (%o5) false (%i6) integerp (%pi); (%o6) false (%i7) integerp (n); (%o7) false (%i8) declare (n, integer); (%o8) done (%i9) integerp (n); (%o9) false  Option variable: m1pbranch   Default value: false' m1pbranch' is the principal branch for -1' to a power. Quantities such as (-1)^(1/3)' (that is, an "odd" rational exponent) and (-1)^(1/4)' (that is, an "even" rational exponent) are handled as follows: domain:real (-1)^(1/3): -1 (-1)^(1/4): (-1)^(1/4) domain:complex m1pbranch:false m1pbranch:true (-1)^(1/3) 1/2+%i*sqrt(3)/2 (-1)^(1/4) sqrt(2)/2+%i*sqrt(2)/2  Function: nonnegintegerp (<n>)   Return true' if and only if <n> >= 0' and <n> is an integer.  Function: numberp (<expr>)   Returns true' if <expr> is a literal integer, rational number, floating point number, or bigfloat, otherwise false'. numberp' returns false' if its argument is a symbol, even if the argument is a symbolic number such as %pi' or %i', or declared to be even', odd', integer', rational', irrational', real', imaginary', or complex'. Examples: (%i1) numberp (42); (%o1) true (%i2) numberp (-13/19); (%o2) true (%i3) numberp (3.14159); (%o3) true (%i4) numberp (-1729b-4); (%o4) true (%i5) map (numberp, [%e, %pi, %i, %phi, inf, minf]); (%o5) [false, false, false, false, false, false] (%i6) declare (a, even, b, odd, c, integer, d, rational, e, irrational, f, real, g, imaginary, h, complex); (%o6) done (%i7) map (numberp, [a, b, c, d, e, f, g, h]); (%o7) [false, false, false, false, false, false, false, false]  Option variable: numer   numer' causes some mathematical functions (including exponentiation) with numerical arguments to be evaluated in floating point. It causes variables in expr' which have been given numerals to be replaced by their values. It also sets the float' switch on. See also %enumer'. Examples: (%i1) [sqrt(2), sin(1), 1/(1+sqrt(3))]; 1 (%o1) [sqrt(2), sin(1), -----------] sqrt(3) + 1 (%i2) [sqrt(2), sin(1), 1/(1+sqrt(3))],numer; (%o2) [1.414213562373095, .8414709848078965, .3660254037844387]  Option variable: numer_pbranch   Default value: false' The option variable numer_pbranch' controls the numerical evaluation of the power of a negative integer, rational, or floating point number. When numer_pbranch' is true' and the exponent is a floating point number or the option variable numer' is true' too, Maxima evaluates the numerical result using the principal branch. Otherwise a simplified, but not an evaluated result is returned. Examples: (%i1) (-2)^0.75; (%o1) (-2)^0.75 (%i2) (-2)^0.75,numer_pbranch:true; (%o2) 1.189207115002721*%i-1.189207115002721 (%i3) (-2)^(3/4); (%o3) (-1)^(3/4)*2^(3/4) (%i4) (-2)^(3/4),numer; (%o4) 1.681792830507429*(-1)^0.75 (%i5) (-2)^(3/4),numer,numer_pbranch:true; (%o5) 1.189207115002721*%i-1.189207115002721  Function: numerval (<x_1>, <expr_1>, ..., <var_n>, <expr_n>)   Declares the variables x_1', ..., <x_n> to have numeric values equal to expr_1', ..., expr_n'. The numeric value is evaluated and substituted for the variable in any expressions in which the variable occurs if the numer' flag is true'. See also ev'. The expressions expr_1', ..., expr_n' can be any expressions, not necessarily numeric.  Function: oddp (<expr>)   is true' if <expr> is an odd integer. false' is returned in all other cases.  Option variable: promote_float_to_bigfloat   Default value: true' When promote_float_to_bigfloat' is true, the result of any floating point calculation that would normally cause a floating point overflow is replaced by a bigfloat number that represents the result. Note that this automatic promotion only happens in interpreted code: compiled code is not affected. This automatic conversion is often convenient, but can be unhelpful in some cases. For example, it can actually cause a loss of precision if fpprec' is currently smaller than the precision in a floating point number. To disable this behaviour, set promote_float_to_bigfloat' to false.  Option variable: ratepsilon   Default value: 2.0e-15' ratepsilon' is the tolerance used in the conversion of floating point numbers to rational numbers, when the option variable bftorat' has the value false'. See bftorat' for an example.  Function: rationalize (<expr>)   Convert all double floats and big floats in the Maxima expression <expr> to their exact rational equivalents. If you are not familiar with the binary representation of floating point numbers, you might be surprised that rationalize (0.1)' does not equal 1/10. This behavior isn't special to Maxima - the number 1/10 has a repeating, not a terminating, binary representation. (%i1) rationalize (0.5); 1 (%o1) - 2 (%i2) rationalize (0.1); 1 (%o2) -- 10 (%i3) fpprec : 5$
(%i4) rationalize (0.1b0);
209715
(%o4)                        -------
2097152
(%i5) fpprec : 20$(%i6) rationalize (0.1b0); 236118324143482260685 (%o6) ---------------------- 2361183241434822606848 (%i7) rationalize (sin (0.1*x + 5.6)); x 28 (%o7) sin(-- + --) 10 5  Function: ratnump (<expr>)   Returns true' if <expr> is a literal integer or ratio of literal integers, otherwise false'.  ## 5.2 Strings  * Introduction to Strings:: * Functions and Variables for Strings::  Function: concat (<arg_1>, <arg_2>, ...)   Concatenates its arguments. The arguments must evaluate to atoms. The return value is a symbol if the first argument is a symbol and a string otherwise. concat' evaluates its arguments. The single quote '' prevents evaluation. (%i1) y: 7$
(%i2) z: 88$(%i3) concat (y, z/2); (%o3) 744 (%i4) concat ('y, z/2); (%o4) y44 A symbol constructed by concat' may be assigned a value and appear in expressions. The ::' (double colon) assignment operator evaluates its left-hand side. (%i5) a: concat ('y, z/2); (%o5) y44 (%i6) a:: 123; (%o6) 123 (%i7) y44; (%o7) 123 (%i8) b^a; y44 (%o8) b (%i9) %, numer; 123 (%o9) b Note that although concat (1, 2)' looks like a number, it is a string. (%i10) concat (1, 2) + 3; (%o10) 12 + 3  Function: sconcat (<arg_1>, <arg_2>, ...)   Concatenates its arguments into a string. Unlike concat', the arguments do not need to be atoms. (%i1) sconcat ("xx[", 3, "]:", expand ((x+y)^3)); (%o1) xx:y^3+3*x*y^2+3*x^2*y+x^3  Function: string (<expr>)   Converts expr' to Maxima's linear notation just as if it had been typed in. The return value of string' is a string, and thus it cannot be used in a computation.  Option variable: stringdisp   Default value: false' When stringdisp' is true', strings are displayed enclosed in double quote marks. Otherwise, quote marks are not displayed. stringdisp' is always true' when displaying a function definition. Examples: (%i1) stringdisp: false$
(%i2) "This is an example string.";
(%o2)              This is an example string.
(%i3) foo () :=
print ("This is a string in a function definition.");
(%o3) foo() :=
print("This is a string in a function definition.")
(%i4) stringdisp: true$(%i5) "This is an example string."; (%o5) "This is an example string."  ## 5.3 Constants  * Functions and Variables for Constants::  Constant: %e   %e' represents the base of the natural logarithm, also known as Euler's number. The numeric value of %e' is the double-precision floating-point value 2.718281828459045d0.  Constant: %i   %i' represents the imaginary unit, sqrt(- 1).  Constant: false   false' represents the Boolean constant of the same name. Maxima implements false' by the value NIL' in Lisp.  Constant: %gamma   The Euler-Mascheroni constant, 0.5772156649015329 ....  Constant: ind   ind' represents a bounded, indefinite result. See also limit'. Example: (%i1) limit (sin(1/x), x, 0); (%o1) ind  Constant: inf   inf' represents real positive infinity.  Constant: infinity   infinity' represents complex infinity.  Constant: minf   minf' represents real minus (i.e., negative) infinity.  Constant: %phi   %phi' represents the so-called golden mean, (1 + sqrt(5))/2. The numeric value of %phi' is the double-precision floating-point value 1.618033988749895d0. fibtophi' expresses Fibonacci numbers fib(n)' in terms of %phi'. By default, Maxima does not know the algebraic properties of %phi'. After evaluating tellrat(%phi^2 - %phi - 1)' and algebraic: true', ratsimp' can simplify some expressions containing %phi'. Examples: fibtophi' expresses Fibonacci numbers fib(n)' in terms of %phi'. (%i1) fibtophi (fib (n)); n n %phi - (1 - %phi) (%o1) ------------------- 2 %phi - 1 (%i2) fib (n-1) + fib (n) - fib (n+1); (%o2) - fib(n + 1) + fib(n) + fib(n - 1) (%i3) fibtophi (%); n + 1 n + 1 n n %phi - (1 - %phi) %phi - (1 - %phi) (%o3) - --------------------------- + ------------------- 2 %phi - 1 2 %phi - 1 n - 1 n - 1 %phi - (1 - %phi) + --------------------------- 2 %phi - 1 (%i4) ratsimp (%); (%o4) 0 By default, Maxima does not know the algebraic properties of %phi'. After evaluating tellrat (%phi^2 - %phi - 1)' and algebraic: true', ratsimp' can simplify some expressions containing %phi'. (%i1) e : expand ((%phi^2 - %phi - 1) * (A + 1)); 2 2 (%o1) %phi A - %phi A - A + %phi - %phi - 1 (%i2) ratsimp (e); 2 2 (%o2) (%phi - %phi - 1) A + %phi - %phi - 1 (%i3) tellrat (%phi^2 - %phi - 1); 2 (%o3) [%phi - %phi - 1] (%i4) algebraic : true; (%o4) true (%i5) ratsimp (e); (%o5) 0  Constant: %pi   %pi' represents the ratio of the perimeter of a circle to its diameter. The numeric value of %pi' is the double-precision floating-point value 3.141592653589793d0.  Constant: true   true' represents the Boolean constant of the same name. Maxima implements true' by the value T' in Lisp.  Constant: und   und' represents an undefined result. See also limit'. Example: (%i1) limit (x*sin(x), x, inf); (%o1) und  Constant: zeroa   zeroa' represents an infinitesimal above zero. zeroa' can be used in expressions. limit' simplifies expressions which contain infinitesimals. See also zerob' and limit'. Example: limit' simplifies expressions which contain infinitesimals: (%i1) limit(zeroa); (%o1) 0 (%i2) limit(x+zeroa); (%o2) x  Constant: zerob   zerob' represents an infinitesimal below zero. zerob' can be used in expressions. limit' simplifies expressions which contain infinitesimals. See also zeroa' and limit'.  ## 5.4 Lists  * Introduction to Lists:: * Functions and Variables for Lists::  Operator: [  Operator: ]   [' and ]' mark the beginning and end, respectively, of a list. [' and ]' also enclose the subscripts of a list, array, hash array, or array function. Examples: (%i1) x: [a, b, c]; (%o1) [a, b, c] (%i2) x; (%o2) c (%i3) array (y, fixnum, 3); (%o3) y (%i4) y: %pi; (%o4) %pi (%i5) y; (%o5) %pi (%i6) z['foo]: 'bar; (%o6) bar (%i7) z['foo]; (%o7) bar (%i8) g[k] := 1/(k^2+1); 1 (%o8) g := ------ k 2 k + 1 (%i9) g; 1 (%o9) --- 101  Function: append (<list_1>, ..., <list_n>)   Returns a single list of the elements of <list_1> followed by the elements of <list_2>, ... append' also works on general expressions, e.g. append (f(a,b), f(c,d,e));' yields f(a,b,c,d,e)'. Do example(append);' for an example.  Function: assoc   assoc (<key>, <list>, <default>) assoc (<key>, <list>) This function searches for <key> in the left hand side of the input <list>. The <list> argument should be a list, each of whose elements is an expression with exactly two parts. Most usually, the elements of <list> are themselves lists, each with two elements. The assoc' function iterates along <list>, checking the first part of each element for equality with <key>. If an element is found where the comparison is true, assoc' returns the second part of that element. If there is no such element in the list, assoc' returns either false' or <default>, if given. For example, in the expression assoc (y, [[x,1], [y,2], [z,3]])', the assoc' function searches for x' in the left hand side of the list [[y,1],[x,2]]' and finds it at the second term, returning 2'. In assoc (z, [[x,1], [z,2], [z,3]])', the search stops at the first term starting with z' and returns 2'. In assoc(x, [[y,1]])', there is no matching element, so assoc' returns false'. (%i1) assoc(y, [[x, 1], [y, 2], [z, 3]]) (%o1) 2 (%i2) assoc(z, [[x, 1], [z, 2], [z, 3]]) (%o2) 2 (%i3) assoc(x, [[y, 1]]) (%o3) false  Function: cons   cons (<expr>, <list>) cons (<expr_1>, <expr_2>) cons (<expr>, <list>)' returns a new list constructed of the element <expr> as its first element, followed by the elements of <list>. This is analogous to the Lisp language construction operation "cons". The Maxima function cons' can also be used where the second argument is other than a list and this might be useful. In this case, cons (<expr_1>, <expr_2>)' returns an expression with same operator as <expr_2> but with argument cons(expr_1, args(expr_2))'. Examples: (%i1) cons(a,[b,c,d]); (%o1) [a, b, c, d] (%i2) cons(a,f(b,c,d)); (%o2) f(a, b, c, d) In general, cons' applied to a nonlist doesn't make sense. For instance, cons(a,b^c)' results in an illegal expression, since '^' cannot take three arguments. When inflag' is true, cons' operates on the internal structure of an expression, otherwise cons' operates on the displayed form. Especially when inflag' is true, cons' applied to a nonlist sometimes gives a surprising result; for example (%i1) cons(a,-a), inflag : true; 2 (%o1) - a (%i2) cons(a,-a), inflag : false; (%o2) 0  Function: copylist (<list>)   Returns a copy of the list <list>.  Function: create_list (<form>, <x_1>, <list_1>, ..., <x_n>, <list_n>)   Create a list by evaluating <form> with <x_1> bound to each element of <list_1>, and for each such binding bind <x_2> to each element of <list_2>, ... The number of elements in the result will be the product of the number of elements in each list. Each variable <x_i> must actually be a symbol - it will not be evaluated. The list arguments will be evaluated once at the beginning of the iteration. (%i1) create_list (x^i, i, [1, 3, 7]); 3 7 (%o1) [x, x , x ] With a double iteration: (%i1) create_list ([i, j], i, [a, b], j, [e, f, h]); (%o1) [[a, e], [a, f], [a, h], [b, e], [b, f], [b, h]] Instead of <list_i> two args may be supplied each of which should evaluate to a number. These will be the inclusive lower and upper bounds for the iteration. (%i1) create_list ([i, j], i, [1, 2, 3], j, 1, i); (%o1) [[1, 1], [2, 1], [2, 2], [3, 1], [3, 2], [3, 3]] Note that the limits or list for the j' variable can depend on the current value of i'.  Function: delete   delete (<expr_1>, <expr_2>) delete (<expr_1>, <expr_2>, <n>) delete(<expr_1>, <expr_2>)' removes from <expr_2> any arguments of its top-level operator which are the same (as determined by "=") as <expr_1>. Note that "=" tests for formal equality, not equivalence. Note also that arguments of subexpressions are not affected. <expr_1> may be an atom or a non-atomic expression. <expr_2> may be any non-atomic expression. delete' returns a new expression; it does not modify <expr_2>. delete(<expr_1>, <expr_2>, <n>)' removes from <expr_2> the first <n> arguments of the top-level operator which are the same as <expr_1>. If there are fewer than <n> such arguments, then all such arguments are removed. Examples: Removing elements from a list. (%i1) delete (y, [w, x, y, z, z, y, x, w]); (%o1) [w, x, z, z, x, w] Removing terms from a sum. (%i1) delete (sin(x), x + sin(x) + y); (%o1) y + x Removing factors from a product. (%i1) delete (u - x, (u - w)*(u - x)*(u - y)*(u - z)); (%o1) (u - w) (u - y) (u - z) Removing arguments from an arbitrary expression. (%i1) delete (a, foo (a, b, c, d, a)); (%o1) foo(b, c, d) Limit the number of removed arguments. (%i1) delete (a, foo (a, b, a, c, d, a), 2); (%o1) foo(b, c, d, a) Whether arguments are the same as <expr_1> is determined by "=". Arguments which are equal' but not "=" are not removed. (%i1) [is (equal (0, 0)), is (equal (0, 0.0)), is (equal (0, 0b0))]; rat: replaced 0.0 by 0/1 = 0.0 rat' replaced 0.0B0 by 0/1 = 0.0B0 (%o1) [true, true, true] (%i2) [is (0 = 0), is (0 = 0.0), is (0 = 0b0)]; (%o2) [true, false, false] (%i3) delete (0, [0, 0.0, 0b0]); (%o3) [0.0, 0.0b0] (%i4) is (equal ((x + y)*(x - y), x^2 - y^2)); (%o4) true (%i5) is ((x + y)*(x - y) = x^2 - y^2); (%o5) false (%i6) delete ((x + y)*(x - y), [(x + y)*(x - y), x^2 - y^2]); 2 2 (%o6) [x - y ]  Function: eighth (<expr>)   Returns the 8'th item of expression or list <expr>. See first' for more details.  Function: endcons   endcons (<expr>, <list>) endcons (<expr_1>, <expr_2>) endcons (<expr>, <list>)' returns a new list constructed of the elements of <list> followed by <expr>. The Maxima function endcons' can also be used where the second argument is other than a list and this might be useful. In this case, endcons (<expr_1>, <expr_2>)' returns an expression with same operator as <expr_2> but with argument endcons(expr_1, args(expr_2))'. Examples: (%i1) endcons(a,[b,c,d]); (%o1) [b, c, d, a] (%i2) endcons(a,f(b,c,d)); (%o2) f(b, c, d, a) In general, endcons' applied to a nonlist doesn't make sense. For instance, endcons(a,b^c)' results in an illegal expression, since '^' cannot take three arguments. When inflag' is true, endcons' operates on the internal structure of an expression, otherwise endcons' operates on the displayed form. Especially when inflag' is true, endcons' applied to a nonlist sometimes gives a surprising result; for example (%i1) endcons(a,-a),inflag : true; 2 (%o1) - a (%i2) endcons(a,-a),inflag : false; (%o2) 0  Function: fifth (<expr>)   Returns the 5'th item of expression or list <expr>. See first' for more details.  Function: first (<expr>)   Returns the first part of <expr> which may result in the first element of a list, the first row of a matrix, the first term of a sum, etc. Note that first' and its related functions, rest' and last', work on the form of <expr> which is displayed not the form which is typed on input. If the variable inflag' is set to true' however, these functions will look at the internal form of <expr>. Note that the simplifier re-orders expressions. Thus first(x+y)' will be x' if inflag' is true' and y' if inflag' is false' (first(y+x)' gives the same results). The functions second' ... tenth' yield the second through the tenth part of their input argument.  Function: fourth (<expr>)   Returns the 4'th item of expression or list <expr>. See first' for more details.  Function: join (<l>, <m>)   Creates a new list containing the elements of lists <l> and <m>, interspersed. The result has elements [<l>, <m>, <l>, <m>, ...]'. The lists <l> and <m> may contain any type of elements. If the lists are different lengths, join' ignores elements of the longer list. Maxima complains if <l> or <m> is not a list. Examples: (%i1) L1: [a, sin(b), c!, d - 1]; (%o1) [a, sin(b), c!, d - 1] (%i2) join (L1, [1, 2, 3, 4]); (%o2) [a, 1, sin(b), 2, c!, 3, d - 1, 4] (%i3) join (L1, [aa, bb, cc, dd, ee, ff]); (%o3) [a, aa, sin(b), bb, c!, cc, d - 1, dd]  Function: last (<expr>)   Returns the last part (term, row, element, etc.) of the <expr>.  Function: length (<expr>)   Returns (by default) the number of parts in the external (displayed) form of <expr>. For lists this is the number of elements, for matrices it is the number of rows, and for sums it is the number of terms (see dispform'). The length' command is affected by the inflag' switch. So, e.g. length(a/(b*c));' gives 2 if inflag' is false' (Assuming exptdispflag' is true'), but 3 if inflag' is true' (the internal representation is essentially a*b^-1*c^-1').  Option variable: listarith   Default value: true' If false' causes any arithmetic operations with lists to be suppressed; when true', list-matrix operations are contagious causing lists to be converted to matrices yielding a result which is always a matrix. However, list-list operations should return lists.  Function: listp (<expr>)   Returns true' if <expr> is a list else false'.  Function: makelist   makelist () makelist (<expr>, <n>) makelist (<expr>, <i>, <i_max>) makelist (<expr>, <i>, <i_0>, <i_max>) makelist (<expr>, <i>, <i_0>, <i_max>, <step>) makelist (<expr>, <x>, <list>) The first form, makelist ()', creates an empty list. The second form, makelist (<expr>)', creates a list with <expr> as its single element. makelist (<expr>, <n>)' creates a list of <n> elements generated from <expr>. The most general form, makelist (<expr>, <i>, <i_0>, <i_max>, <step>)', returns the list of elements obtained when ev (<expr>, <i>=<j>)' is applied to the elements <j> of the sequence: <i_0>, <i_0> + <step>, <i_0> + 2*<step>, ..., with <|j|> less than or equal to <|i_max|>. The increment <step> can be a number (positive or negative) or an expression. If it is omitted, the default value 1 will be used. If both <i_0> and <step> are omitted, they will both have a default value of 1. makelist (<expr>, <x>, <list>)' returns a list, the j''th element of which is equal to ev (<expr>, <x>=<list>[j])' for j' equal to 1 through length (<list>)'. Examples: (%i1) makelist (concat (x,i), i, 6); (%o1) [x1, x2, x3, x4, x5, x6] (%i2) makelist (x=y, y, [a, b, c]); (%o2) [x = a, x = b, x = c] (%i3) makelist (x^2, x, 3, 2*%pi, 2); (%o3) [9, 25] (%i4) makelist (random(6), 4); (%o4) [2, 0, 2, 5] (%i5) flatten (makelist (makelist (i^2, 3), i, 4)); (%o5) [1, 1, 1, 4, 4, 4, 9, 9, 9, 16, 16, 16] (%i6) flatten (makelist (makelist (i^2, i, 3), 4)); (%o6) [1, 4, 9, 1, 4, 9, 1, 4, 9, 1, 4, 9]  Function: member (<expr_1>, <expr_2>)   Returns true' if is(<expr_1> = <a>)' for some element <a> in args(<expr_2>)', otherwise returns false'. expr_2' is typically a list, in which case args(<expr_2>) = <expr_2>' and is(<expr_1> = <a>)' for some element <a> in expr_2' is the test. member' does not inspect parts of the arguments of expr_2', so it may return false' even if expr_1' is a part of some argument of expr_2'. See also elementp'. Examples: (%i1) member (8, [8, 8.0, 8b0]); (%o1) true (%i2) member (8, [8.0, 8b0]); (%o2) false (%i3) member (b, [a, b, c]); (%o3) true (%i4) member (b, [[a, b], [b, c]]); (%o4) false (%i5) member ([b, c], [[a, b], [b, c]]); (%o5) true (%i6) F (1, 1/2, 1/4, 1/8); 1 1 1 (%o6) F(1, -, -, -) 2 4 8 (%i7) member (1/8, %); (%o7) true (%i8) member ("ab", ["aa", "ab", sin(1), a + b]); (%o8) true  Function: ninth (<expr>)   Returns the 9'th item of expression or list <expr>. See first' for more details.  Function: pop (<list>)   pop' removes and returns the first element from the list <list>. The second argument <list> must be a mapatom that is bound to a nonempty list. If the argument <list> is not bound to a nonempty list, Maxima signals an error. For examples, see push'.  Function: push (<item>, <list>)   push' prepends the item <item> to the list <list> and returns a copy of the new list. The second argument <list> must be a mapatom that is bound to a list. The first argument <item> can be any Maxima symbol or expression. If the argument <list> is not bound to a list, Maxima signals an error. To remove the first item from a list, see pop'. Examples: (%i1) ll : []; (%o1) [] (%i2) push(x,ll); (%o2) [x] (%i3) push(x^2+y,ll); 2 (%o3) [y + x , x] (%i4) push("string",ll); 2 (%o4) [string, y + x , x] (%i5) pop(ll); (%o5) string (%i6) pop(ll); 2 (%o6) y + x (%i7) pop(ll); (%o7) x (%i8) ll; (%o8) [] (%i9)  Function: rest   rest (<expr>, <n>) rest (<expr>) Returns <expr> with its first <n> elements removed if <n> is positive and its last - <n>' elements removed if <n> is negative. If <n> is 1 it may be omitted. The first argument <expr> may be a list, matrix, or other expression. When <expr> is a mapatom, rest' signals an error; when <expr> is an empty list and partswitch' is false, rest' signals an error. When <expr> is an empty list and partswitch' is true, rest' returns end'. Applying rest' to expression such as f(a,b,c)' returns f(b,c)'. In general, applying rest' to an nonlist doesn't make sense. For example, because '^' requires two arguments, rest(a^b)' results in an error message. The functions args' and op' may be useful as well, since args(a^b)' returns [a,b]' and op(a^b)' returns ^. (%i1) rest(a+b+c); (%o1) b+a (%i2) rest(a+b+c,2); (%o2) a (%i3) rest(a+b+c,-2); (%o3) c  Function: reverse (<list>)   Reverses the order of the members of the <list> (not the members themselves). reverse' also works on general expressions, e.g. reverse(a=b);' gives b=a'.  Function: second (<expr>)   Returns the 2'nd item of expression or list <expr>. See first' for more details.  Function: seventh (<expr>)   Returns the 7'th item of expression or list <expr>. See first' for more details.  Function: sixth (<expr>)   Returns the 6'th item of expression or list <expr>. See first' for more details.  Function: sort   sort (<L>, <P>) sort (<L>) sort(<L>, <P>)' sorts a list <L> according to a predicate P' of two arguments which defines a strict weak order on the elements of <L>. If <P>(a, b)' is true', then a' appears before b' in the result. If neither <P>(a, b)' nor <P>(b, a)' are true', then a' and b' are equivalent, and appear in the result in the same order as in the input. That is, sort' is a stable sort. If <P>(a, b)' and <P>(b, a)' are both true' for some elements of <L>, then <P> is not a valid sort predicate, and the result is undefined. If <P>(a, b)' is something other than true' or false', sort' signals an error. The predicate may be specified as the name of a function or binary infix operator, or as a lambda' expression. If specified as the name of an operator, the name must be enclosed in double quotes. The sorted list is returned as a new object; the argument <L> is not modified. sort(<L>)' is equivalent to sort(<L>, orderlessp)'. The default sorting order is ascending, as determined by orderlessp'. The predicate ordergreatp' sorts a list in descending order. All Maxima atoms and expressions are comparable under orderlessp' and ordergreatp'. Operators <' and >' order numbers, constants, and constant expressions by magnitude. Note that orderlessp' and ordergreatp' do not order numbers, constants, and constant expressions by magnitude. ordermagnitudep' orders numbers, constants, and constant expressions the same as <', and all other elements the same as orderlessp'. Examples: sort' sorts a list according to a predicate of two arguments which defines a strict weak order on the elements of the list. (%i1) sort ([1, a, b, 2, 3, c], 'orderlessp); (%o1) [1, 2, 3, a, b, c] (%i2) sort ([1, a, b, 2, 3, c], 'ordergreatp); (%o2) [c, b, a, 3, 2, 1] The predicate may be specified as the name of a function or binary infix operator, or as a lambda' expression. If specified as the name of an operator, the name must be enclosed in double quotes. (%i1) L : [[1, x], [3, y], [4, w], [2, z]]; (%o1) [[1, x], [3, y], [4, w], [2, z]] (%i2) foo (a, b) := a > b; (%o2) foo(a, b) := a > b 1 1 (%i3) sort (L, 'foo); (%o3) [[4, w], [3, y], [2, z], [1, x]] (%i4) infix (">>"); (%o4) >> (%i5) a >> b := a > b; (%o5) a >> b := a > b 1 1 (%i6) sort (L, ">>"); (%o6) [[4, w], [3, y], [2, z], [1, x]] (%i7) sort (L, lambda ([a, b], a > b)); (%o7) [[4, w], [3, y], [2, z], [1, x]] sort(<L>)' is equivalent to sort(<L>, orderlessp)'. (%i1) L : [a, 2*b, -5, 7, 1 + %e, %pi]; (%o1) [a, 2 b, - 5, 7, %e + 1, %pi] (%i2) sort (L); (%o2) [- 5, 7, %e + 1, %pi, a, 2 b] (%i3) sort (L, 'orderlessp); (%o3) [- 5, 7, %e + 1, %pi, a, 2 b] The default sorting order is ascending, as determined by orderlessp'. The predicate ordergreatp' sorts a list in descending order. (%i1) L : [a, 2*b, -5, 7, 1 + %e, %pi]; (%o1) [a, 2 b, - 5, 7, %e + 1, %pi] (%i2) sort (L); (%o2) [- 5, 7, %e + 1, %pi, a, 2 b] (%i3) sort (L, 'ordergreatp); (%o3) [2 b, a, %pi, %e + 1, 7, - 5] All Maxima atoms and expressions are comparable under orderlessp' and ordergreatp'. (%i1) L : [11, -17, 29b0, 9*c, 7.55, foo(x, y), -5/2, b + a]; 5 (%o1) [11, - 17, 2.9b1, 9 c, 7.55, foo(x, y), - -, b + a] 2 (%i2) sort (L, orderlessp); 5 (%o2) [- 17, - -, 7.55, 11, 2.9b1, b + a, 9 c, foo(x, y)] 2 (%i3) sort (L, ordergreatp); 5 (%o3) [foo(x, y), 9 c, b + a, 2.9b1, 11, 7.55, - -, - 17] 2 Operators <' and >' order numbers, constants, and constant expressions by magnitude. Note that orderlessp' and ordergreatp' do not order numbers, constants, and constant expressions by magnitude. (%i1) L : [%pi, 3, 4, %e, %gamma]; (%o1) [%pi, 3, 4, %e, %gamma] (%i2) sort (L, ">"); (%o2) [4, %pi, 3, %e, %gamma] (%i3) sort (L, ordergreatp); (%o3) [%pi, %gamma, %e, 4, 3] ordermagnitudep' orders numbers, constants, and constant expressions the same as <', and all other elements the same as orderlessp'. (%i1) L : [%i, 1+%i, 2*x, minf, inf, %e, sin(1), 0, 1, 2, 3, 1.0, 1.0b0]; (%o1) [%i, %i + 1, 2 x, minf, inf, %e, sin(1), 0, 1, 2, 3, 1.0, 1.0b0] (%i2) sort (L, ordermagnitudep); (%o2) [minf, 0, sin(1), 1, 1.0, 1.0b0, 2, %e, 3, inf, %i, %i + 1, 2 x] (%i3) sort (L, orderlessp); (%o3) [0, 1, 1.0, 2, 3, %e, %i, %i + 1, inf, minf, sin(1), 1.0b0, 2 x]  Function: sublist (<list>, <p>)   Returns the list of elements of <list> for which the predicate p' returns true'. Example: (%i1) L: [1, 2, 3, 4, 5, 6]; (%o1) [1, 2, 3, 4, 5, 6] (%i2) sublist (L, evenp); (%o2) [2, 4, 6]  Function: sublist_indices (<L>, <P>)   Returns the indices of the elements x' of the list <L> for which the predicate maybe(<P>(x))' returns true'; this excludes unknown' as well as false'. <P> may be the name of a function or a lambda expression. <L> must be a literal list. Examples: (%i1) sublist_indices ('[a, b, b, c, 1, 2, b, 3, b], lambda ([x], x='b)); (%o1) [2, 3, 7, 9] (%i2) sublist_indices ('[a, b, b, c, 1, 2, b, 3, b], symbolp); (%o2) [1, 2, 3, 4, 7, 9] (%i3) sublist_indices ([1 > 0, 1 < 0, 2 < 1, 2 > 1, 2 > 0], identity); (%o3) [1, 4, 5] (%i4) assume (x < -1); (%o4) [x < - 1] (%i5) map (maybe, [x > 0, x < 0, x < -2]); (%o5) [false, true, unknown] (%i6) sublist_indices ([x > 0, x < 0, x < -2], identity); (%o6)   Function: unique (<L>)   Returns the unique elements of the list <L>. When all the elements of <L> are unique, unique' returns a shallow copy of <L>, not <L> itself. If <L> is not a list, unique' returns <L>. Example: (%i1) unique ([1, %pi, a + b, 2, 1, %e, %pi, a + b, ]); (%o1) [1, 2, %e, %pi, , b + a]  Function: tenth (<expr>)   Returns the 10'th item of expression or list <expr>. See first' for more details.  Function: third (<expr>)   Returns the 3'rd item of expression or list <expr>. See first' for more details.  ## 5.5 Arrays  * Functions and Variables for Arrays::  Function: array   array (<name>, <dim_1>, ..., <dim_n>) array (<name>, <type>, <dim_1>, ..., <dim_n>) array ([<name_1>, ..., <name_m>], <dim_1>, ..., <dim_n>) Creates an n-dimensional array. n may be less than or equal to 5. The subscripts for the i'th dimension are the integers running from 0 to <dim_i>. array (<name>, <dim_1>, ..., <dim_n>)' creates a general array. array (<name>, <type>, <dim_1>, ..., <dim_n>)' creates an array, with elements of a specified type. <type> can be fixnum' for integers of limited size or flonum' for floating-point numbers. array ([<name_1>, ..., <name_m>], <dim_1>, ..., <dim_n>)' creates m arrays, all of the same dimensions. If the user assigns to a subscripted variable before declaring the corresponding array, an undeclared array is created. Undeclared arrays, otherwise known as hashed arrays (because hash coding is done on the subscripts), are more general than declared arrays. The user does not declare their maximum size, and they grow dynamically by hashing as more elements are assigned values. The subscripts of undeclared arrays need not even be numbers. However, unless an array is rather sparse, it is probably more efficient to declare it when possible than to leave it undeclared. The array' function can be used to transform an undeclared array into a declared array.  Function: arrayapply (<A>, [<i_1>, ..., <i_n>])   Evaluates <A> [<i_1>, ..., <i_n>]', where <A> is an array and <i_1>, ..., <i_n> are integers. This is reminiscent of apply', except the first argument is an array instead of a function.  Function: arrayinfo (<A>)   Returns information about the array <A>. The argument <A> may be a declared array, an undeclared (hashed) array, an array function, or a subscripted function. For declared arrays, arrayinfo' returns a list comprising the atom declared', the number of dimensions, and the size of each dimension. The elements of the array, both bound and unbound, are returned by listarray'. For undeclared arrays (hashed arrays), arrayinfo' returns a list comprising the atom hashed', the number of subscripts, and the subscripts of every element which has a value. The values are returned by listarray'. For array functions, arrayinfo' returns a list comprising the atom hashed', the number of subscripts, and any subscript values for which there are stored function values. The stored function values are returned by listarray'. For subscripted functions, arrayinfo' returns a list comprising the atom hashed', the number of subscripts, and any subscript values for which there are lambda expressions. The lambda expressions are returned by listarray'. See also listarray'. Examples: arrayinfo' and listarray' applied to a declared array. (%i1) array (aa, 2, 3); (%o1) aa (%i2) aa [2, 3] : %pi; (%o2) %pi (%i3) aa [1, 2] : %e; (%o3) %e (%i4) arrayinfo (aa); (%o4) [declared, 2, [2, 3]] (%i5) listarray (aa); (%o5) [#####, #####, #####, #####, #####, #####, %e, #####, #####, #####, #####, %pi] arrayinfo' and listarray' applied to an undeclared (hashed) array. (%i1) bb [FOO] : (a + b)^2; 2 (%o1) (b + a) (%i2) bb [BAR] : (c - d)^3; 3 (%o2) (c - d) (%i3) arrayinfo (bb); (%o3) [hashed, 1, [BAR], [FOO]] (%i4) listarray (bb); 3 2 (%o4) [(c - d) , (b + a) ] arrayinfo' and listarray' applied to an array function. (%i1) cc [x, y] := y / x; y (%o1) cc := - x, y x (%i2) cc [u, v]; v (%o2) - u (%i3) cc [4, z]; z (%o3) - 4 (%i4) arrayinfo (cc); (%o4) [hashed, 2, [4, z], [u, v]] (%i5) listarray (cc); z v (%o5) [-, -] 4 u arrayinfo' and listarray' applied to a subscripted function. (%i1) dd [x] (y) := y ^ x; x (%o1) dd (y) := y x (%i2) dd [a + b]; b + a (%o2) lambda([y], y ) (%i3) dd [v - u]; v - u (%o3) lambda([y], y ) (%i4) arrayinfo (dd); (%o4) [hashed, 1, [b + a], [v - u]] (%i5) listarray (dd); b + a v - u (%o5) [lambda([y], y ), lambda([y], y )]  Function: arraymake (<A>, [<i_1>, ..., <i_n>])   Returns the expression <A>[<i_1>, ..., <i_n>]'. The result is an unevaluated array reference. arraymake' is reminiscent of funmake', except the return value is an unevaluated array reference instead of an unevaluated function call. Examples: (%i1) arraymake (A, ); (%o1) A 1 (%i2) arraymake (A, [k]); (%o2) A k (%i3) arraymake (A, [i, j, 3]); (%o3) A i, j, 3 (%i4) array (A, fixnum, 10); (%o4) A (%i5) fillarray (A, makelist (i^2, i, 1, 11)); (%o5) A (%i6) arraymake (A, ); (%o6) A 5 (%i7) ''%; (%o7) 36 (%i8) L : [a, b, c, d, e]; (%o8) [a, b, c, d, e] (%i9) arraymake ('L, [n]); (%o9) L n (%i10) ''%, n = 3; (%o10) c (%i11) A2 : make_array (fixnum, 10); (%o11) {Array: #(0 0 0 0 0 0 0 0 0 0)} (%i12) fillarray (A2, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]); (%o12) {Array: #(1 2 3 4 5 6 7 8 9 10)} (%i13) arraymake ('A2, ); (%o13) A2 8 (%i14) ''%; (%o14) 9  System variable: arrays   Default value: []' arrays' is a list of arrays that have been allocated. These comprise arrays declared by array', hashed arrays constructed by implicit definition (assigning something to an array element), and array functions defined by :=' and define'. Arrays defined by make_array' are not included. See also array', arrayapply', arrayinfo', arraymake', fillarray', listarray', and rearray'. Examples: (%i1) array (aa, 5, 7); (%o1) aa (%i2) bb [FOO] : (a + b)^2; 2 (%o2) (b + a) (%i3) cc [x] := x/100; x (%o3) cc := --- x 100 (%i4) dd : make_array ('any, 7); (%o4) {Array: #(NIL NIL NIL NIL NIL NIL NIL)} (%i5) arrays; (%o5) [aa, bb, cc]  Function: arraysetapply (<A>, [<i_1>, ..., <i_n>], <x>)   Assigns <x> to <A>[<i_1>, ..., <i_n>]', where <A> is an array and <i_1>, ..., <i_n> are integers. arraysetapply' evaluates its arguments.  Function: fillarray (<A>, <B>)   Fills array <A> from <B>, which is a list or an array. If a specific type was declared for <A> when it was created, it can only be filled with elements of that same type; it is an error if an attempt is made to copy an element of a different type. If the dimensions of the arrays <A> and <B> are different, <A> is filled in row-major order. If there are not enough elements in <B> the last element is used to fill out the rest of <A>. If there are too many, the remaining ones are ignored. fillarray' returns its first argument. Examples: Create an array of 9 elements and fill it from a list. (%i1) array (a1, fixnum, 8); (%o1) a1 (%i2) listarray (a1); (%o2) [0, 0, 0, 0, 0, 0, 0, 0, 0] (%i3) fillarray (a1, [1, 2, 3, 4, 5, 6, 7, 8, 9]); (%o3) a1 (%i4) listarray (a1); (%o4) [1, 2, 3, 4, 5, 6, 7, 8, 9] When there are too few elements to fill the array, the last element is repeated. When there are too many elements, the extra elements are ignored. (%i1) a2 : make_array (fixnum, 8); (%o1) {Array: #(0 0 0 0 0 0 0 0)} (%i2) fillarray (a2, [1, 2, 3, 4, 5]); (%o2) {Array: #(1 2 3 4 5 5 5 5)} (%i3) fillarray (a2, ); (%o3) {Array: #(4 4 4 4 4 4 4 4)} (%i4) fillarray (a2, makelist (i, i, 1, 100)); (%o4) {Array: #(1 2 3 4 5 6 7 8)} Multple-dimension arrays are filled in row-major order. (%i1) a3 : make_array (fixnum, 2, 5); (%o1) {Array: #2A((0 0 0 0 0) (0 0 0 0 0))} (%i2) fillarray (a3, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]); (%o2) {Array: #2A((1 2 3 4 5) (6 7 8 9 10))} (%i3) a4 : make_array (fixnum, 5, 2); (%o3) {Array: #2A((0 0) (0 0) (0 0) (0 0) (0 0))} (%i4) fillarray (a4, a3); (%o4) {Array: #2A((1 2) (3 4) (5 6) (7 8) (9 10))}  Function: listarray (<A>)   Returns a list of the elements of the array <A>. The argument <A> may be a declared array, an undeclared (hashed) array, an array function, or a subscripted function. Elements are listed in row-major order. That is, elements are sorted according to the first index, then according to the second index, and so on. The sorting order of index values is the same as the order established by orderless'. For undeclared arrays, array functions, and subscripted functions, the elements correspond to the index values returned by arrayinfo'. Unbound elements of declared general arrays (that is, not fixnum' and not flonum') are returned as #####'. Unbound elements of declared fixnum' or flonum' arrays are returned as 0 or 0.0, respectively. Unbound elements of undeclared arrays, array functions, and subscripted functions are not returned. Examples: listarray' and arrayinfo' applied to a declared array. (%i1) array (aa, 2, 3); (%o1) aa (%i2) aa [2, 3] : %pi; (%o2) %pi (%i3) aa [1, 2] : %e; (%o3) %e (%i4) listarray (aa); (%o4) [#####, #####, #####, #####, #####, #####, %e, #####, #####, #####, #####, %pi] (%i5) arrayinfo (aa); (%o5) [declared, 2, [2, 3]] listarray' and arrayinfo' applied to an undeclared (hashed) array. (%i1) bb [FOO] : (a + b)^2; 2 (%o1) (b + a) (%i2) bb [BAR] : (c - d)^3; 3 (%o2) (c - d) (%i3) listarray (bb); 3 2 (%o3) [(c - d) , (b + a) ] (%i4) arrayinfo (bb); (%o4) [hashed, 1, [BAR], [FOO]] listarray' and arrayinfo' applied to an array function. (%i1) cc [x, y] := y / x; y (%o1) cc := - x, y x (%i2) cc [u, v]; v (%o2) - u (%i3) cc [4, z]; z (%o3) - 4 (%i4) listarray (cc); z v (%o4) [-, -] 4 u (%i5) arrayinfo (cc); (%o5) [hashed, 2, [4, z], [u, v]] listarray' and arrayinfo' applied to a subscripted function. (%i1) dd [x] (y) := y ^ x; x (%o1) dd (y) := y x (%i2) dd [a + b]; b + a (%o2) lambda([y], y ) (%i3) dd [v - u]; v - u (%o3) lambda([y], y ) (%i4) listarray (dd); b + a v - u (%o4) [lambda([y], y ), lambda([y], y )] (%i5) arrayinfo (dd); (%o5) [hashed, 1, [b + a], [v - u]]  Function: make_array (<type>, <dim_1>, ..., <dim_n>)   Creates and returns a Lisp array. <type> may be any', flonum', fixnum', hashed' or functional'. There are n indices, and the i'th index runs from 0 to <dim_i> - 1. The advantage of make_array' over array' is that the return value doesn't have a name, and once a pointer to it goes away, it will also go away. For example, if y: make_array (...)' then y' points to an object which takes up space, but after y: false', y' no longer points to that object, so the object can be garbage collected. Examples: (%i1) A1 : make_array (fixnum, 10); (%o1) {Array: #(0 0 0 0 0 0 0 0 0 0)} (%i2) A1  : 1729; (%o2) 1729 (%i3) A1; (%o3) {Array: #(0 0 0 0 0 0 0 0 1729 0)} (%i4) A2 : make_array (flonum, 10); (%o4) {Array: #(0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0)} (%i5) A2  : 2.718281828; (%o5) 2.718281828 (%i6) A2; (%o6) {Array: #(0.0 0.0 2.718281828 0.0 0.0 0.0 0.0 0.0 0.0 0.0)} (%i7) A3 : make_array (any, 10); (%o7) {Array: #(NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL)} (%i8) A3  : x - y - z; (%o8) - z - y + x (%i9) A3; (%o9) {Array: #(NIL NIL NIL NIL ((MPLUS SIMP)$X ((MTIMES SIMP)\
-1 $Y) ((MTIMES SIMP) -1$Z))
NIL NIL NIL NIL NIL)}
(%i10) A4 : make_array (fixnum, 2, 3, 5);
(%o10) {Array:  #3A(((0 0 0 0 0) (0 0 0 0 0) (0 0 0 0 0)) ((0 0 \
0 0 0) (0 0 0 0 0) (0 0 0 0 0)))}
(%i11) fillarray (A4, makelist (i, i, 1, 2*3*5));
(%o11) {Array:  #3A(((1 2 3 4 5) (6 7 8 9 10) (11 12 13 14 15))
((16 17 18 19 20) (21 22 23 24 25) (26 27 28 29 30)))}
(%i12) A4 [0, 2, 1];
(%o12)                         12


Function: rearray (<A>, <dim_1>, ..., <dim_n>)

     Changes the dimensions of an array.  The new array will be filled
with the elements of the old one in row-major order.  If the old
array was too small, the remaining elements are filled with
false', 0.0' or 0', depending on the type of the array.  The
type of the array cannot be changed.


Function: remarray

          remarray (<A_1>, ..., <A_n>)
remarray (all)
Removes arrays and array associated functions and frees the
storage occupied.  The arguments may be declared arrays,
undeclared (hashed) arrays, array functions, and subscripted
functions.

remarray (all)' removes all items in the global list arrays'.

It may be necessary to use this function if it is desired to
redefine the values in a hashed array.

remarray' returns the list of arrays removed.

remarray' quotes its arguments.


Function: subvar (<x>, <i>)

     Evaluates the subscripted expression <x>[<i>]'.

subvar' evaluates its arguments.

arraymake (<x>, [<i>])' constructs the expression <x>[<i>]', but
does not evaluate it.

Examples:

(%i1) x : foo $(%i2) i : 3$
(%i3) subvar (x, i);
(%o3)                         foo
3
(%i4) foo : [aa, bb, cc, dd, ee]$(%i5) subvar (x, i); (%o5) cc (%i6) arraymake (x, [i]); (%o6) foo 3 (%i7) ''%; (%o7) cc  Function: subvarp (<expr>)   Returns true' if <expr> is a subscripted variable, for example a[i]'.  Option variable: use_fast_arrays   If true' then only two types of arrays are recognized: 1. The art-q array (t in Common Lisp) which may have several dimensions indexed by integers, and may hold any Lisp or Maxima object as an entry. To construct such an array, enter a:make_array(any,3,4);' then a' will have as value, an array with twelve slots, and the indexing is zero based. 2. The Hash_table array which is the default type of array created if one does b[x+1]:y^2' (and b' is not already an array, a list, or a matrix - if it were one of these an error would be caused since x+1' would not be a valid subscript for an art-q array, a list or a matrix). Its indices (also known as keys) may be any object. It only takes one key at a time (b[x+1,u]:y' would ignore the u'). Referencing is done by b[x+1] ==> y^2'. Of course the key may be a list, e.g. b[[x+1,u]]:y' would be valid. This is incompatible with the old Maxima hash arrays, but saves consing. An advantage of storing the arrays as values of the symbol is that the usual conventions about local variables of a function apply to arrays as well. The Hash_table type also uses less consing and is more efficient than the old type of Maxima hashar. To obtain consistent behaviour in translated and compiled code set translate_fast_arrays' to be true'.  ## 5.6 Structures  * Introduction to Structures:: * Functions and Variables for Structures::  Global variable: structures   structures' is the list of user-defined structures defined by defstruct'.  Function: defstruct   defstruct (<S>(<a_1>, ..., <a_n>)) defstruct (<S>(<a_1> = <v_1>, ..., <a_n> = <v_n>)) Define a structure, which is a list of named fields <a_1>, ..., <a_n> associated with a symbol <S>. An instance of a structure is just an expression which has operator <S> and exactly n' arguments. new(<S>)' creates a new instance of structure <S>. An argument which is just a symbol <a> specifies the name of a field. An argument which is an equation <a> = <v>' specifies the field name <a> and its default value <v>. The default value can be any expression. defstruct' puts <S> on the list of user-defined structures, structures'. kill(<S>)' removes <S> from the list of user-defined structures, and removes the structure definition. Examples: (%i1) defstruct (foo (a, b, c)); (%o1) [foo(a, b, c)] (%i2) structures; (%o2) [foo(a, b, c)] (%i3) new (foo); (%o3) foo(a, b, c) (%i4) defstruct (bar (v, w, x = 123, y = %pi)); (%o4) [bar(v, w, x = 123, y = %pi)] (%i5) structures; (%o5) [foo(a, b, c), bar(v, w, x = 123, y = %pi)] (%i6) new (bar); (%o6) bar(v, w, x = 123, y = %pi) (%i7) kill (foo); (%o7) done (%i8) structures; (%o8) [bar(v, w, x = 123, y = %pi)]  Function: new   new (<S>) new (<S> (<v_1>, ..., <v_n>)) new' creates new instances of structures. new(<S>)' creates a new instance of structure <S> in which each field is assigned its default value, if any, or no value at all if no default was specified in the structure definition. new(<S>(<v_1>, ..., <v_n>))' creates a new instance of <S> in which fields are assigned the values <v_1>, ..., <v_n>. Examples: (%i1) defstruct (foo (w, x = %e, y = 42, z)); (%o1) [foo(w, x = %e, y = 42, z)] (%i2) new (foo); (%o2) foo(w, x = %e, y = 42, z) (%i3) new (foo (1, 2, 4, 8)); (%o3) foo(w = 1, x = 2, y = 4, z = 8)  Operator: @   @' is the structure field access operator. The expression <x>@ <a>' refers to the value of field <a> of the structure instance <x>. The field name is not evaluated. If the field <a> in <x> has not been assigned a value, <x>@ <a>' evaluates to itself. kill(<x>@ <a>)' removes the value of field <a> in <x>. Examples: (%i1) defstruct (foo (x, y, z)); (%o1) [foo(x, y, z)] (%i2) u : new (foo (123, a - b, %pi)); (%o2) foo(x = 123, y = a - b, z = %pi) (%i3) u@z; (%o3) %pi (%i4) u@z : %e; (%o4) %e (%i5) u; (%o5) foo(x = 123, y = a - b, z = %e) (%i6) kill (u@z); (%o6) done (%i7) u; (%o7) foo(x = 123, y = a - b, z) (%i8) u@z; (%o8) u@z The field name is not evaluated. (%i1) defstruct (bar (g, h)); (%o1) [bar(g, h)] (%i2) x : new (bar); (%o2) bar(g, h) (%i3) x@h : 42; (%o3) 42 (%i4) h : 123; (%o4) 123 (%i5) x@h; (%o5) 42 (%i6) x@h : 19; (%o6) 19 (%i7) x; (%o7) bar(g, h = 19) (%i8) h; (%o8) 123  ## 6 Expressions  Introduction to Expressions Nouns and Verbs Identifiers Inequality Functions and Variables for Expressions  ## 6.1 Introduction to Expressions There are a number of reserved words which should not be used as variable names. Their use would cause a possibly cryptic syntax error. integrate next from diff in at limit sum for and elseif then else do or if unless product while thru step Most things in Maxima are expressions. A sequence of expressions can be made into an expression by separating them by commas and putting parentheses around them. This is similar to the C comma expression. (%i1) x: 3$
(%i2) (x: x+1, x: x^2);
(%o2)                          16
(%i3) (if (x > 17) then 2 else 4);
(%o3)                           4
(%i4) (if (x > 17) then x: 2 else y: 4, y+x);
(%o4)                          20

Even loops in Maxima are expressions, although the value they return
is the not too useful done'.

(%i1) y: (x: 1, for i from 1 thru 10 do (x: x*i))$(%i2) y; (%o2) done Whereas what you really want is probably to include a third term in the comma expression which actually gives back the value. (%i3) y: (x: 1, for i from 1 thru 10 do (x: x*i), x)$
(%i4) y;
(%o4)                        3628800


## 6.2 Nouns and Verbs

Maxima distinguishes between operators which are "nouns" and operators
which are "verbs".  A verb is an operator which can be executed.  A
noun is an operator which appears as a symbol in an expression, without
being executed.  By default, function names are verbs.  A verb can be
changed into a noun by quoting the function name or applying the
nounify' function.  A noun can be changed into a verb by applying the
verbify' function.  The evaluation flag nouns' causes ev' to
evaluate nouns in an expression.

The verb form is distinguished by a leading dollar sign $' on the corresponding Lisp symbol. In contrast, the noun form is distinguished by a leading percent sign %' on the corresponding Lisp symbol. Some nouns have special display properties, such as 'integrate' and 'derivative' (returned by diff'), but most do not. By default, the noun and verb forms of a function are identical when displayed. The global flag noundisp' causes Maxima to display nouns with a leading quote mark ''. See also noun', nouns', nounify', and verbify'. Examples: (%i1) foo (x) := x^2; 2 (%o1) foo(x) := x (%i2) foo (42); (%o2) 1764 (%i3) 'foo (42); (%o3) foo(42) (%i4) 'foo (42), nouns; (%o4) 1764 (%i5) declare (bar, noun); (%o5) done (%i6) bar (x) := x/17; x (%o6) ''bar(x) := -- 17 (%i7) bar (52); (%o7) bar(52) (%i8) bar (52), nouns; 52 (%o8) -- 17 (%i9) integrate (1/x, x, 1, 42); (%o9) log(42) (%i10) 'integrate (1/x, x, 1, 42); 42 / [ 1 (%o10) I - dx ] x / 1 (%i11) ev (%, nouns); (%o11) log(42)  ## 6.3 Identifiers Maxima identifiers may comprise alphabetic characters, plus the numerals 0 through 9, plus any special character preceded by the backslash \' character. A numeral may be the first character of an identifier if it is preceded by a backslash. Numerals which are the second or later characters need not be preceded by a backslash. Characters may be declared alphabetic by the declare' function. If so declared, they need not be preceded by a backslash in an identifier. The alphabetic characters are initially A' through Z', a' through z', %', and _'. Maxima is case-sensitive. The identifiers foo', FOO', and Foo' are distinct. See *note Lisp and Maxima:: for more on this point. A Maxima identifier is a Lisp symbol which begins with a dollar sign $'.  Any other Lisp symbol is preceded by a question mark ?' when it
appears in Maxima.  See *note Lisp and Maxima:: for more on this point.

Examples:

(%i1) %an_ordinary_identifier42;
(%o1)               %an_ordinary_identifier42
(%i2) embedded\ spaces\ in\ an\ identifier;
(%o2)           embedded spaces in an identifier
(%i3) symbolp (%);
(%o3)                         true
(%i4) [foo+bar, foo\+bar];
(%o4)                 [foo + bar, foo+bar]
(%i5) [1729, \1729];
(%o5)                     [1729, 1729]
(%i6) [symbolp (foo\+bar), symbolp (\1729)];
(%o6)                     [true, true]
(%i7) [is (foo\+bar = foo+bar), is (\1729 = 1729)];
(%o7)                    [false, false]
(%i8) baz\~quux;
(%o8)                       baz~quux
(%i9) declare ("~", alphabetic);
(%o9)                         done
(%i10) baz~quux;
(%o10)                      baz~quux
(%i11) [is (foo = FOO), is (FOO = Foo), is (Foo = foo)];
(%o11)                [false, false, false]
(%i12) :lisp (defvar *my-lisp-variable* '$foo) *MY-LISP-VARIABLE* (%i12) ?\*my\-lisp\-variable\*; (%o12) foo  ## 6.4 Inequality Maxima has the inequality operators <', <=', >=', >', #', and notequal'. See if' for a description of conditional expressions.  ## 6.5 Functions and Variables for Expressions Function: alias (<new_name_1>, <old_name_1>, ..., <new_name_n>, <old_name_n>)   provides an alternate name for a (user or system) function, variable, array, etc. Any even number of arguments may be used.  System variable: aliases   Default value: []' aliases' is the list of atoms which have a user defined alias (set up by the alias', ordergreat', orderless' functions or by declaring the atom a noun' with declare'.)  Keyword: allbut   works with the part' commands (i.e. part', inpart', substpart', substinpart', dpart', and lpart'). For example, (%i1) expr : e + d + c + b + a; (%o1) e + d + c + b + a (%i2) part (expr, [2, 5]); (%o2) d + a while (%i1) expr : e + d + c + b + a; (%o1) e + d + c + b + a (%i2) part (expr, allbut (2, 5)); (%o2) e + c + b allbut' is also recognized by kill'. (%i1) [aa : 11, bb : 22, cc : 33, dd : 44, ee : 55]; (%o1) [11, 22, 33, 44, 55] (%i2) kill (allbut (cc, dd)); (%o0) done (%i1) [aa, bb, cc, dd]; (%o1) [aa, bb, 33, 44] kill(allbut(<a_1>, <a_2>, ...))' has the effect of kill(all)' except that it does not kill the symbols <a_1>, <a_2>, ...  Function: args (<expr>)   Returns the list of arguments of expr', which may be any kind of expression other than an atom. Only the arguments of the top-level operator are extracted; subexpressions of expr' appear as elements or subexpressions of elements of the list of arguments. The order of the items in the list may depend on the global flag inflag'. args (<expr>)' is equivalent to substpart ("[", <expr>, 0)'. See also substpart', and op'.  Function: atom (<expr>)   Returns true' if <expr> is atomic (i.e. a number, name or string) else false'. Thus atom(5)' is true' while atom(a)' and atom(sin(x))' are false' (assuming a' and x' are unbound).  Function: box   box (<expr>) box (<expr>, <a>) Returns <expr> enclosed in a box. The return value is an expression with box' as the operator and <expr> as the argument. A box is drawn on the display when display2d' is true'. box (<expr>, <a>)' encloses <expr> in a box labelled by the symbol <a>. The label is truncated if it is longer than the width of the box. box' evaluates its argument. However, a boxed expression does not evaluate to its content, so boxed expressions are effectively excluded from computations. boxchar' is the character used to draw the box in box' and in the dpart' and lpart' functions. Examples: (%i1) box (a^2 + b^2); """"""""" " 2 2" (%o1) "b + a " """"""""" (%i2) a : 1234; (%o2) 1234 (%i3) b : c - d; (%o3) c - d (%i4) box (a^2 + b^2); """""""""""""""""""" " 2 " (%o4) "(c - d) + 1522756" """""""""""""""""""" (%i5) box (a^2 + b^2, term_1); term_1"""""""""""""" " 2 " (%o5) "(c - d) + 1522756" """""""""""""""""""" (%i6) 1729 - box (1729); """""" (%o6) 1729 - "1729" """""" (%i7) boxchar: "-"; (%o7) - (%i8) box (sin(x) + cos(y)); ----------------- (%o8) -cos(y) + sin(x)- -----------------  Option variable: boxchar   Default value: "' boxchar' is the character used to draw the box in the box' and in the dpart' and lpart' functions. All boxes in an expression are drawn with the current value of boxchar'; the drawing character is not stored with the box expression.  Function: collapse (<expr>)   Collapses <expr> by causing all of its common (i.e., equal) subexpressions to share (i.e., use the same cells), thereby saving space. (collapse' is a subroutine used by the optimize' command.) Thus, calling collapse' may be useful after loading in a save' file. You can collapse several expressions together by using collapse ([<expr_1>, ..., <expr_n>])'. Similarly, you can collapse the elements of the array A' by doing collapse (listarray ('A))'.  Function: disolate (<expr>, <x_1>, ..., <x_n>)   is similar to isolate (<expr>, <x>)' except that it enables the user to isolate more than one variable simultaneously. This might be useful, for example, if one were attempting to change variables in a multiple integration, and that variable change involved two or more of the integration variables. This function is autoloaded from simplification/disol.mac'. A demo is available by demo("disol")$'.


Function: dispform

          dispform (<expr>)
dispform (<expr>, all)
Returns the external representation of <expr>.

dispform(<expr>)' returns the external representation with
respect to the main (top-level) operator.  dispform(<expr>, all)'
returns the external representation with respect to all operators
in <expr>.

See also part', inpart', and inflag'.

Examples:

The internal representation of - x' is "negative one times x'"
while the external representation is "minus x'".

(%i1) - x;
(%o1)                          - x
(%i2) ?format (true, "~S~%", %);
((MTIMES SIMP) -1 $X) (%o2) false (%i3) dispform (- x); (%o3) - x (%i4) ?format (true, "~S~%", %); ((MMINUS SIMP)$X)
(%o4)                         false

The internal representation of sqrt(x)' is "x' to the power 1/2"
while the external representation is "square root of x'".

(%i1) sqrt (x);
(%o1)                        sqrt(x)
(%i2) ?format (true, "~S~%", %);
((MEXPT SIMP) $X ((RAT SIMP) 1 2)) (%o2) false (%i3) dispform (sqrt (x)); (%o3) sqrt(x) (%i4) ?format (true, "~S~%", %); ((%SQRT SIMP)$X)
(%o4)                         false

Use of the optional argument all'.

(%i1) expr : sin (sqrt (x));
(%o1)                     sin(sqrt(x))
(%i2) freeof (sqrt, expr);
(%o2)                         true
(%i3) freeof (sqrt, dispform (expr));
(%o3)                         true
(%i4) freeof (sqrt, dispform (expr, all));
(%o4)                         false


Function: dpart (<expr>, <n_1>, ..., <n_k>)

     Selects the same subexpression as part', but instead of just
returning that subexpression as its value, it returns the whole
expression with the selected subexpression displayed inside a box.
The box is actually part of the expression.

(%i1) dpart (x+y/z^2, 1, 2, 1);
y
(%o1)                       ---- + x
2
"""
"z"
"""


Option variable: exptisolate

     Default value: false'

exptisolate', when true', causes isolate (expr, var)' to
examine exponents of atoms (such as %e') which contain var'.


Option variable: exptsubst

     Default value: false'

exptsubst', when true', permits substitutions such as y' for
%e^x' in %e^(a x)'.

(%i1) %e^(a*x);
a x
(%o1)                                %e
(%i2) exptsubst;
(%o2)                                false
(%i3) subst(y, %e^x, %e^(a*x));
a x
(%o3)                                %e
(%i4) exptsubst: not exptsubst;
(%o4)                                true
(%i5) subst(y, %e^x, %e^(a*x));
a
(%o5)                                 y


Function: freeof (<x_1>, ..., <x_n>, <expr>)

     freeof (<x_1>, <expr>)' returns true' if no subexpression of
<expr> is equal to <x_1> or if <x_1> occurs only as a dummy
variable in <expr>, or if <x_1> is neither the noun nor verb form
of any operator in <expr>, and returns false' otherwise.

freeof (<x_1>, ..., <x_n>, <expr>)' is equivalent to freeof
(<x_1>, <expr>) and ... and freeof (<x_n>, <expr>)'.

The arguments <x_1>, ..., <x_n> may be names of functions and
variables, subscripted names, operators (enclosed in double
quotes), or general expressions.  freeof' evaluates its arguments.

freeof' operates only on <expr> as it stands (after
simplification and evaluation) and does not attempt to determine
if some equivalent expression would give a different result.  In
particular, simplification may yield an equivalent but different
expression which comprises some different elements than the
original form of <expr>.

A variable is a dummy variable in an expression if it has no
binding outside of the expression.  Dummy variables recognized by
freeof' are the index of a sum or product, the limit variable in
limit', the integration variable in the definite integral form of
integrate', the original variable in laplace', formal variables
in at' expressions, and arguments in lambda' expressions.

The indefinite form of integrate' is not free of its variable of
integration.

Examples:

Arguments are names of functions, variables, subscripted names,
operators, and expressions.  freeof (a, b, expr)' is equivalent to
freeof (a, expr) and freeof (b, expr)'.

(%i1) expr: z^3 * cos (a) * b^(c+d);
d + c  3
(%o1)                   cos(a ) b      z
1
(%i2) freeof (z, expr);
(%o2)                         false
(%i3) freeof (cos, expr);
(%o3)                         false
(%i4) freeof (a, expr);
(%o4)                         false
(%i5) freeof (cos (a), expr);
(%o5)                         false
(%i6) freeof (b^(c+d), expr);
(%o6)                         false
(%i7) freeof ("^", expr);
(%o7)                         false
(%i8) freeof (w, sin, a, sin (a), b*(c+d), expr);
(%o8)                         true

freeof' evaluates its arguments.

(%i1) expr: (a+b)^5$(%i2) c: a$
(%i3) freeof (c, expr);
(%o3)                         false

freeof' does not consider equivalent expressions.  Simplification
may yield an equivalent but different expression.

(%i1) expr: (a+b)^5$(%i2) expand (expr); 5 4 2 3 3 2 4 5 (%o2) b + 5 a b + 10 a b + 10 a b + 5 a b + a (%i3) freeof (a+b, %); (%o3) true (%i4) freeof (a+b, expr); (%o4) false (%i5) exp (x); x (%o5) %e (%i6) freeof (exp, exp (x)); (%o6) true A summation or definite integral is free of its dummy variable. An indefinite integral is not free of its variable of integration. (%i1) freeof (i, 'sum (f(i), i, 0, n)); (%o1) true (%i2) freeof (x, 'integrate (x^2, x, 0, 1)); (%o2) true (%i3) freeof (x, 'integrate (x^2, x)); (%o3) false  Option variable: inflag   Default value: false' When inflag' is true', functions for part extraction inspect the internal form of expr'. Note that the simplifier re-orders expressions. Thus first (x + y)' returns x' if inflag' is true' and y' if inflag' is false'. (first (y + x)' gives the same results.) Also, setting inflag' to true' and calling part' or substpart' is the same as calling inpart' or substinpart'. Functions affected by the setting of inflag' are: part', substpart', first', rest', last', length', the for' ... in' construct, map', fullmap', maplist', reveal' and pickapart'.  Function: inpart (<expr>, <n_1>, ..., <n_k>)   is similar to part' but works on the internal representation of the expression rather than the displayed form and thus may be faster since no formatting is done. Care should be taken with respect to the order of subexpressions in sums and products (since the order of variables in the internal form is often different from that in the displayed form) and in dealing with unary minus, subtraction, and division (since these operators are removed from the expression). part (x+y, 0)' or inpart (x+y, 0)' yield +', though in order to refer to the operator it must be enclosed in "s. For example ... if inpart (%o9,0) = "+" then ...'. Examples: (%i1) x + y + w*z; (%o1) w z + y + x (%i2) inpart (%, 3, 2); (%o2) z (%i3) part (%th (2), 1, 2); (%o3) z (%i4) 'limit (f(x)^g(x+1), x, 0, minus); g(x + 1) (%o4) limit f(x) x -> 0- (%i5) inpart (%, 1, 2); (%o5) g(x + 1)  Function: isolate (<expr>, <x>)   Returns <expr> with subexpressions which are sums and which do not contain <var> replaced by intermediate expression labels (these being atomic symbols like %t1', %t2', ...). This is often useful to avoid unnecessary expansion of subexpressions which don't contain the variable of interest. Since the intermediate labels are bound to the subexpressions they can all be substituted back by evaluating the expression in which they occur. exptisolate' (default value: false') if true' will cause isolate' to examine exponents of atoms (like %e') which contain <var>. isolate_wrt_times' if true', then isolate' will also isolate with respect to products. See isolate_wrt_times'. Do example (isolate)' for examples.  Option variable: isolate_wrt_times   Default value: false' When isolate_wrt_times' is true', isolate' will also isolate with respect to products. E.g. compare both settings of the switch on (%i1) isolate_wrt_times: true$
(%i2) isolate (expand ((a+b+c)^2), c);

(%t2)                          2 a


Option variable: listconstvars

     Default value: false'

When listconstvars' is true' the list returned by listofvars'
contains constant variables, such as %e', %pi', %i' or any
variables declared as constant that occur in <expr>. A variable is
declared as constant' type via declare', and constantp' returns
true' for all variables declared as constant'. The default is to
omit constant variables from listofvars' return value.

Example:

(%i1) lfreeof ([ a, x], x^2+b);
(%o1)                                false
lfreeof ([ b, x], x^2+b);
(%o2)                                false
lfreeof ([ a, y], x^2+b);
(%o3)                                true


Option variable: listdummyvars

     Default value: true'

When listdummyvars' is false', "dummy variables" in the
expression will not be included in the list returned by
listofvars'.  (The meaning of "dummy variables" is as given in
freeof'.  "Dummy variables" are mathematical things like the
index of a sum or product, the limit variable, and the definite
integration variable.)

Example:

(%i1) listdummyvars: true$(%i2) listofvars ('sum(f(i), i, 0, n)); (%o2) [i, n] (%i3) listdummyvars: false$
(%i4) listofvars ('sum(f(i), i, 0, n));
(%o4)                          [n]


Function: listofvars (<expr>)

     Returns a list of the variables in <expr>.

listconstvars' if true' causes listofvars' to include %e',
%pi', %i', and any variables declared constant in the list it
returns if they appear in <expr>.  The default is to omit these.

"dummy variables" in the list of variables.

(%i1) listofvars (f (x+y) / g^(2+a));
(%o1)                     [g, a, x , y]
1


Function: lfreeof (<list>, <expr>)

     For each member <m> of <list>, calls freeof (<m>, <expr>)'.  It
returns false' if any call to freeof' does and true' otherwise.


Function: lpart (<label>, <expr>, <n_1>, ..., <n_k>)

     is similar to dpart' but uses a labelled box.  A labelled box is
similar to the one produced by dpart' but it has a name in the
top line.


Property: mainvar

     You may declare variables to be mainvar'.  The ordering scale for
atoms is essentially: numbers < constants (e.g., %e', %pi') <
scalars < other variables < mainvars.  E.g., compare expand
((X+Y)^4)' with (declare (x, mainvar), expand ((x+y)^4))'.
(Note: Care should be taken if you elect to use the above feature.
E.g., if you subtract an expression in which x' is a mainvar'
from one in which x' isn't a mainvar', resimplification e.g.
with ev (expr, simp)' may be necessary if cancellation is to
occur.  Also, if you save an expression in which x' is a
mainvar', you probably should also save x'.)


Property: noun

     noun' is one of the options of the declare' command.  It makes a
function so declared a "noun", meaning that it won't be evaluated
automatically.

Example:

(%i1) factor (12345678);
2
(%o1)                     2 3  47 14593
(%i2) declare (factor, noun);
(%o2)                         done
(%i3) factor (12345678);
(%o3)                   factor(12345678)
(%i4) ''%, nouns;
2
(%o4)                     2 3  47 14593


Option variable: noundisp

     Default value: false'

When noundisp' is true', nouns display with a single quote.
This switch is always true' when displaying function definitions.


Function: nounify (<f>)

     Returns the noun form of the function name <f>.  This is needed if
one wishes to refer to the name of a verb function as if it were a
noun.  Note that some verb functions will return their noun forms
if they can't be evaluated for certain arguments.  This is also
the form returned if a function call is preceded by a quote.


Function: nterms (<expr>)

     Returns the number of terms that <expr> would have if it were fully
expanded out and no cancellations or combination of terms occurred.
Note that expressions like sin (<expr>)', sqrt (<expr>)', exp
(<expr>)', etc. count as just one term regardless of how many
terms <expr> has (if it is a sum).


Function: op (<expr>)

     Returns the main operator of the expression <expr>.  op (<expr>)'
is equivalent to part (<expr>, 0)'.

op' returns a string if the main operator is a built-in or
user-defined prefix, binary or n-ary infix, postfix, matchfix, or
nofix operator.  Otherwise, if <expr> is a subscripted function
expression, op' returns the subscripted function; in this case
the return value is not an atom.  Otherwise, <expr> is an array
function or ordinary function expression, and op' returns a
symbol.

op' observes the value of the global flag inflag'.

op' evaluates it argument.

Examples:

(%i1) stringdisp: true$(%i2) op (a * b * c); (%o2) "*" (%i3) op (a * b + c); (%o3) "+" (%i4) op ('sin (a + b)); (%o4) sin (%i5) op (a!); (%o5) "!" (%i6) op (-a); (%o6) "-" (%i7) op ([a, b, c]); (%o7) "[" (%i8) op ('(if a > b then c else d)); (%o8) "if" (%i9) op ('foo (a)); (%o9) foo (%i10) prefix (foo); (%o10) "foo" (%i11) op (foo a); (%o11) "foo" (%i12) op (F [x, y] (a, b, c)); (%o12) F x, y (%i13) op (G [u, v, w]); (%o13) G  Function: operatorp   operatorp (<expr>, <op>) operatorp (<expr>, [<op_1>, ..., <op_n>]) operatorp (<expr>, <op>)' returns true' if <op> is equal to the operator of <expr>. operatorp (<expr>, [<op_1>, ..., <op_n>])' returns true' if some element <op_1>, ..., <op_n> is equal to the operator of <expr>.  Option variable: opsubst   Default value: true' When opsubst' is false', subst' does not attempt to substitute into the operator of an expression. E.g., (opsubst: false, subst (x^2, r, r+r))' will work. (%i1) r+r; (%o1) r + r 0 (%i2) opsubst; (%o2) true (%i3) subst (x^2, r, r+r); 2 2 (%o3) x + (x ) 0 (%i4) opsubst: not opsubst; (%o4) false (%i5) subst (x^2, r, r+r); 2 (%o5) x + r 0  Function: optimize (<expr>)   Returns an expression that produces the same value and side effects as <expr> but does so more efficiently by avoiding the recomputation of common subexpressions. optimize' also has the side effect of "collapsing" its argument so that all common subexpressions are shared. Do example (optimize)' for examples.  Option variable: optimprefix   Default value: %' optimprefix' is the prefix used for generated symbols by the optimize' command.  Function: ordergreat (<v_1>, ..., <v_n>)  Function: orderless (<v_1>, ..., <v_n>)   ordergreat' changes the canonical ordering of Maxima expressions such that <v_1> succeeds <v_2> succeeds ... succeeds <v_n>, and <v_n> succeeds any other symbol not mentioned as an argument. orderless' changes the canonical ordering of Maxima expressions such that <v_1> precedes <v_2> precedes ... precedes <v_n>, and <v_n> precedes any other variable not mentioned as an argument. The order established by ordergreat' and orderless' is dissolved by unorder'. ordergreat' and orderless' can be called only once each, unless unorder' is called; only the last call to ordergreat' and orderless' has any effect. See also ordergreatp'.  Function: ordergreatp (<expr_1>, <expr_2>)  Function: orderlessp (<expr_1>, <expr_2>)   ordergreatp' returns true' if <expr_1> succeeds <expr_2> in the canonical ordering of Maxima expressions, and false' otherwise. orderlessp' returns true' if <expr_1> precedes <expr_2> in the canonical ordering of Maxima expressions, and false' otherwise. All Maxima atoms and expressions are comparable under ordergreatp' and orderlessp', although there are isolated examples of expressions for which these predicates are not transitive; that is a bug. The canonical ordering of atoms (symbols, literal numbers, and strings) is the following. (integers and floats) precede (bigfloats) precede (declared constants) precede (strings) precede (declared scalars) precede (first argument to orderless') precedes ... precedes (last argument to orderless') precedes (other symbols) precede (last argument to ordergreat') precedes ... precedes (first argument to ordergreat') precedes (declared main variables) For non-atomic expressions, the canonical ordering is derived from the ordering for atoms. For the built-in +' *' and ^' operators, the ordering is not easily summarized. For other built-in operators and all other functions and operators, expressions are ordered by their arguments (beginning with the first argument), then by the name of the operator or function. In the case of subscripted expressions, the subscripted symbol is considered the operator and the subscript is considered an argument. The canonical ordering of expressions is modified by the functions ordergreat' and orderless', and the mainvar', constant', and scalar' declarations. See also sort'. Examples: Ordering ordinary symbols and constants. Note that %pi' is not ordered according to its numerical value. (%i1) stringdisp : true; (%o1) true (%i2) sort([%pi, 3b0, 3.0, x, X, "foo", 3, a, 4, "bar", 4.0, 4b0]); (%o2) [3, 3.0, 4, 4.0, 3.0b0, 4.0b0, %pi, "bar", "foo", a, x, X] Effect of ordergreat' and orderless' functions. (%i1) sort ([M, H, K, T, E, W, G, A, P, J, S]); (%o1) [A, E, G, H, J, K, M, P, S, T, W] (%i2) ordergreat (S, J); (%o2) done (%i3) orderless (M, H); (%o3) done (%i4) sort ([M, H, K, T, E, W, G, A, P, J, S]); (%o4) [M, H, A, E, G, K, P, T, W, J, S] Effect of mainvar', constant', and scalar' declarations. (%i1) sort ([aa, foo, bar, bb, baz, quux, cc, dd, A1, B1, C1]); (%o1) [aa, bar, baz, bb, cc, dd, foo, quux, A1, B1, C1] (%i2) declare (aa, mainvar); (%o2) done (%i3) declare ([baz, quux], constant); (%o3) done (%i4) declare ([A1, B1], scalar); (%o4) done (%i5) sort ([aa, foo, bar, bb, baz, quux, cc, dd, A1, B1, C1]); (%o5) [baz, quux, A1, B1, bar, bb, cc, dd, foo, C1, aa] Ordering non-atomic expressions. (%i1) sort([1, 2, n, f(1), f(2), f(2, 1), g(1), g(1, 2), g(n), f(n, 1)]); (%o1) [1, 2, f(1), g(1), g(1, 2), f(2), f(2, 1), n, g(n), f(n, 1)] (%i2) sort ([foo(1), X, X[k], foo(k), 1, k]); (%o2) [1, foo(1), X , k, foo(k), X ] 1 k  Function: part (<expr>, <n_1>, ..., <n_k>)   Returns parts of the displayed form of expr'. It obtains the part of expr' as specified by the indices <n_1>, ..., <n_k>. First part <n_1> of expr' is obtained, then part <n_2> of that, etc. The result is part <n_k> of ... part <n_2> of part <n_1> of expr'. If no indices are specified expr' is returned. part' can be used to obtain an element of a list, a row of a matrix, etc. If the last argument to a part' function is a list of indices then several subexpressions are picked out, each one corresponding to an index of the list. Thus part (x + y + z, [1, 3])' is z+x'. piece' holds the last expression selected when using the part' functions. It is set during the execution of the function and thus may be referred to in the function itself as shown below. If partswitch' is set to true' then end' is returned when a selected part of an expression doesn't exist, otherwise an error message is given. See also inpart', substpart', substinpart', dpart', and lpart'. Examples: (%i1) part(z+2*y+a,2); (%o1) 2 y (%i2) part(z+2*y+a,[1,3]); (%o2) z + a (%i3) part(z+2*y+a,2,1); (%o3) 2 example (part)' displays additional examples.  Function: partition (<expr>, <x>)   Returns a list of two expressions. They are (1) the factors of <expr> (if it is a product), the terms of <expr> (if it is a sum), or the list (if it is a list) which don't contain <x> and, (2) the factors, terms, or list which do. Examples: (%i1) partition (2*a*x*f(x), x); (%o1) [2 a, x f(x)] (%i2) partition (a+b, x); (%o2) [b + a, 0] (%i3) partition ([a, b, f(a), c], a); (%o3) [[b, c], [a, f(a)]]  Option variable: partswitch   Default value: false' When partswitch' is true', end' is returned when a selected part of an expression doesn't exist, otherwise an error message is given.  Function: pickapart (<expr>, <n>)   Assigns intermediate expression labels to subexpressions of <expr> at depth <n>, an integer. Subexpressions at greater or lesser depths are not assigned labels. pickapart' returns an expression in terms of intermediate expressions equivalent to the original expression <expr>. See also part', dpart', lpart', inpart', and reveal'. Examples: (%i1) expr: (a+b)/2 + sin (x^2)/3 - log (1 + sqrt(x+1)); 2 sin(x ) b + a (%o1) - log(sqrt(x + 1) + 1) + ------- + ----- 3 2 (%i2) pickapart (expr, 0); 2 sin(x ) b + a (%t2) - log(sqrt(x + 1) + 1) + ------- + ----- 3 2 (%o2) %t2 (%i3) pickapart (expr, 1); (%t3) - log(sqrt(x + 1) + 1)  System variable: piece   Holds the last expression selected when using the part' functions. It is set during the execution of the function and thus may be referred to in the function itself.  Function: psubst   psubst (<list>, <expr>) psubst (<a>, <b>, <expr>) psubst(<a>, <b>, <expr>)' is simliar to subst'. See subst'. In distinction from subst' the function psubst' makes parallel substitutions, if the first argument <list> is a list of equations. See also sublis' for making parallel substitutions. Example: The first example shows parallel substitution with psubst'. The second example shows the result for the function subst', which does a serial substitution. (%i4) psubst ([a^2=b, b=a], sin(a^2) + sin(b)); (%o4) sin(b) + sin(a) (%i5) subst ([a^2=b, b=a], sin(a^2) + sin(b)); (%o5) 2 sin(a)  Function: rembox   rembox (<expr>, unlabelled) rembox (<expr>, <label>) rembox (<expr>) Removes boxes from <expr>. rembox (<expr>, unlabelled)' removes all unlabelled boxes from <expr>. rembox (<expr>, <label>)' removes only boxes bearing <label>. rembox (<expr>)' removes all boxes, labelled and unlabelled. Boxes are drawn by the box', dpart', and lpart' functions. Examples: (%i1) expr: (a*d - b*c)/h^2 + sin(%pi*x); a d - b c (%o1) sin(%pi x) + --------- 2 h (%i2) dpart (dpart (expr, 1, 1), 2, 2); """"""" a d - b c (%o2) sin("%pi x") + --------- """"""" """" " 2" "h " """" (%i3) expr2: lpart (BAR, lpart (FOO, %, 1), 2); FOO""""""""""" BAR"""""""" " """"""" " "a d - b c" (%o3) "sin("%pi x")" + "---------" " """"""" " " """" " """""""""""""" " " 2" " " "h " " " """" " """"""""""" (%i4) rembox (expr2, unlabelled); BAR"""""""" FOO""""""""" "a d - b c" (%o4) "sin(%pi x)" + "---------" """""""""""" " 2 " " h " """"""""""" (%i5) rembox (expr2, FOO); BAR"""""""" """"""" "a d - b c" (%o5) sin("%pi x") + "---------" """"""" " """" " " " 2" " " "h " " " """" " """"""""""" (%i6) rembox (expr2, BAR); FOO""""""""""" " """"""" " a d - b c (%o6) "sin("%pi x")" + --------- " """"""" " """" """""""""""""" " 2" "h " """" (%i7) rembox (expr2); a d - b c (%o7) sin(%pi x) + --------- 2 h  Function: reveal (<expr>, <depth>)   Replaces parts of <expr> at the specified integer <depth> with descriptive summaries. * Sums and differences are replaced by Sum(<n>)' where <n> is the number of operands of the sum. * Products are replaced by Product(<n>)' where <n> is the number of operands of the product. * Exponentials are replaced by Expt'. * Quotients are replaced by Quotient'. * Unary negation is replaced by Negterm'. * Lists are replaced by List(<n>)' where <n> ist the number of elements of the list. When <depth> is greater than or equal to the maximum depth of <expr>, reveal (<expr>, <depth>)' returns <expr> unmodified. reveal' evaluates its arguments. reveal' returns the summarized expression. Example: (%i1) e: expand ((a - b)^2)/expand ((exp(a) + exp(b))^2); 2 2 b - 2 a b + a (%o1) ------------------------- b + a 2 b 2 a 2 %e + %e + %e (%i2) reveal (e, 1); (%o2) Quotient (%i3) reveal (e, 2); Sum(3) (%o3) ------ Sum(3) (%i4) reveal (e, 3); Expt + Negterm + Expt (%o4) ------------------------ Product(2) + Expt + Expt (%i5) reveal (e, 4); 2 2 b - Product(3) + a (%o5) ------------------------------------ Product(2) Product(2) 2 Expt + %e + %e (%i6) reveal (e, 5); 2 2 b - 2 a b + a (%o6) -------------------------- Sum(2) 2 b 2 a 2 %e + %e + %e (%i7) reveal (e, 6); 2 2 b - 2 a b + a (%o7) ------------------------- b + a 2 b 2 a 2 %e + %e + %e  Function: sublis (<list>, <expr>)   Makes multiple parallel substitutions into an expression. <list> is a list of equations. The left hand side of the equations must be an atom. The variable sublis_apply_lambda' controls simplification after sublis'. See also psubst' for making parallel substitutions. Example: (%i1) sublis ([a=b, b=a], sin(a) + cos(b)); (%o1) sin(b) + cos(a)  Option variable: sublis_apply_lambda   Default value: true' Controls whether lambda''s substituted are applied in simplification after sublis' is used or whether you have to do an ev' to get things to apply. true' means do the application.  Option variable: subnumsimp   Default value: false' If true' then the functions subst' and psubst' can substitute a subscripted variable f[x]' with a number, when only the symbol f' is given. See also subst'. (%i1) subst(100,g,g[x]+2); subst: cannot substitute 100 for operator g in expression g x -- an error. To debug this try: debugmode(true); (%i2) subst(100,g,g[x]+2),subnumsimp:true; (%o2) 102  Function: subst (<a>, <b>, <c>)   Substitutes <a> for <b> in <c>. <b> must be an atom or a complete subexpression of <c>. For example, x+y+z' is a complete subexpression of 2*(x+y+z)/w' while x+y' is not. When <b> does not have these characteristics, one may sometimes use substpart' or ratsubst' (see below). Alternatively, if <b> is of the form e/f' then one could use subst (a*f, e, c)' while if <b> is of the form e^(1/f)' then one could use subst (a^f, e, c)'. The subst' command also discerns the x^y' in x^-y' so that subst (a, sqrt(x), 1/sqrt(x))' yields 1/a'. <a> and <b> may also be operators of an expression enclosed in double-quotes "' or they may be function names. If one wishes to substitute for the independent variable in derivative forms then the at' function (see below) should be used. subst' is an alias for substitute'. The commands subst (<eq_1>, <expr>)' or subst ([<eq_1>, ..., <eq_k>], <expr>)' are other permissible forms. The <eq_i> are equations indicating substitutions to be made. For each equation, the right side will be substituted for the left in the expression <expr>. The equations are substituted in serial from left to right in <expr>. See the functions sublis' and psubst' for making parallel substitutions. exptsubst' if true' permits substitutions like y' for %e^x' in %e^(a*x)' to take place. When opsubst' is false', subst' will not attempt to substitute into the operator of an expression. E.g. (opsubst: false, subst (x^2, r, r+r))' will work. Examples: (%i1) subst (a, x+y, x + (x+y)^2 + y); 2 (%o1) y + x + a (%i2) subst (-%i, %i, a + b*%i); (%o2) a - %i b The substitution is done in serial for a list of equations. Compare this with a parallel substitution: (%i3) subst([a=b, b=c], a+b); (%o3) 2 c (%i4) sublis([a=b, b=c], a+b); (%o4) c + b For further examples, do example (subst)'.  Function: substinpart (<x>, <expr>, <n_1>, ..., <n_k>)   Similar to substpart', but substinpart' works on the internal representation of <expr>. Examples: (%i1) x . 'diff (f(x), x, 2); 2 d (%o1) x . (--- (f(x))) 2 dx (%i2) substinpart (d^2, %, 2); 2 (%o2) x . d (%i3) substinpart (f1, f(x + 1), 0); (%o3) f1(x + 1) If the last argument to a part' function is a list of indices then several subexpressions are picked out, each one corresponding to an index of the list. Thus (%i1) part (x + y + z, [1, 3]); (%o1) z + x piece' holds the value of the last expression selected when using the part' functions. It is set during the execution of the function and thus may be referred to in the function itself as shown below. If partswitch' is set to true' then end' is returned when a selected part of an expression doesn't exist, otherwise an error message is given. (%i1) expr: 27*y^3 + 54*x*y^2 + 36*x^2*y + y + 8*x^3 + x + 1; 3 2 2 3 (%o1) 27 y + 54 x y + 36 x y + y + 8 x + x + 1 (%i2) part (expr, 2, [1, 3]); 2 (%o2) 54 y (%i3) sqrt (piece/54); (%o3) abs(y) (%i4) substpart (factor (piece), expr, [1, 2, 3, 5]); 3 (%o4) (3 y + 2 x) + y + x + 1 (%i5) expr: 1/x + y/x - 1/z; 1 y 1 (%o5) - - + - + - z x x (%i6) substpart (xthru (piece), expr, [2, 3]); y + 1 1 (%o6) ----- - - x z Also, setting the option inflag' to true' and calling part' or substpart' is the same as calling inpart' or substinpart'.  Function: substpart (<x>, <expr>, <n_1>, ..., <n_k>)   Substitutes <x> for the subexpression picked out by the rest of the arguments as in part'. It returns the new value of <expr>. <x> may be some operator to be substituted for an operator of <expr>. In some cases <x> needs to be enclosed in double-quotes "' (e.g. substpart ("+", a*b, 0)' yields b + a'). Example: (%i1) 1/(x^2 + 2); 1 (%o1) ------ 2 x + 2 (%i2) substpart (3/2, %, 2, 1, 2); 1 (%o2) -------- 3/2 x + 2 (%i3) a*x + f(b, y); (%o3) a x + f(b, y) (%i4) substpart ("+", %, 1, 0); (%o4) x + f(b, y) + a Also, setting the option inflag' to true' and calling part' or substpart' is the same as calling inpart' or substinpart'.  Function: symbolp (<expr>)   Returns true' if <expr> is a symbol, else false'. In effect, symbolp(x)' is equivalent to the predicate atom(x) and not numberp(x)'. See also *note Identifiers::.  Function: unorder ()   Disables the aliasing created by the last use of the ordering commands ordergreat' and orderless'. ordergreat' and orderless' may not be used more than one time each without calling unorder'. unorder' does not substitute back in expressions the original symbols for the aliases introduced by ordergreat' and orderless'. Therefore, after execution of unorder' the aliases appear in previous expressions. See also ordergreat' and orderless'. Examples: ordergreat(a)' introduces an alias for the symbol a'. Therefore, the difference of %o2' and %o4' does not vanish. unorder' does not substitute back the symbol a' and the alias appears in the output %o7'. (%i1) unorder(); (%o1) [] (%i2) b*x+a^2; 2 (%o2) b x + a (%i3) ordergreat(a); (%o3) done (%i4) b*x+a^2; 2 (%o4) a + b x (%i5) %th(1)-%th(3); 2 2 (%o5) a - a (%i6) unorder(); (%o6) [a] (%i7) %th(2); 2 2 (%o7) _101a - a  Function: verbify (<f>)   Returns the verb form of the function name <f>. See also verb', noun', and nounify'. Examples: (%i1) verbify ('foo); (%o1) foo (%i2) :lisp$%
$FOO (%i2) nounify (foo); (%o2) foo (%i3) :lisp$%
%FOO



## 7 Operators


Introduction to operators
Arithmetic operators
Relational operators
Logical operators
Operators for Equations
Assignment operators
User defined operators


## 7.1 Introduction to operators

It is possible to define new operators with specified precedence, to
undefine existing operators, or to redefine the precedence of existing
operators.  An operator may be unary prefix or unary postfix, binary
infix, n-ary infix, matchfix, or nofix.  "Matchfix" means a pair of
symbols which enclose their argument or arguments, and "nofix" means an
operator which takes no arguments.  As examples of the different types
of operators, there are the following.

unary prefix
negation - a'

unary postfix
factorial a!'

binary infix
exponentiation a^b'

n-ary infix

matchfix
list construction [a, b]'

(There are no built-in nofix operators; for an example of such an
operator, see nofix'.)

The mechanism to define a new operator is straightforward.  It is
only necessary to declare a function as an operator; the operator
function might or might not be defined.

An example of user-defined operators is the following.  Note that
the explicit function call "dd" (a)' is equivalent to dd a', likewise
"<-" (a, b)' is equivalent to a <- b'.  Note also that the functions
"dd"' and "<-"' are undefined in this example.

(%i1) prefix ("dd");
(%o1)                          dd
(%i2) dd a;
(%o2)                         dd a
(%i3) "dd" (a);
(%o3)                         dd a
(%i4) infix ("<-");
(%o4)                          <-
(%i5) a <- dd b;
(%o5)                      a <- dd b
(%i6) "<-" (a, "dd" (b));
(%o6)                      a <- dd b

The Maxima functions which define new operators are summarized in
this table, stating the default left and right binding powers (lbp and
rbp, respectively).  (Binding power determines operator precedence.
However, since left and right binding powers can differ, binding power
is somewhat more complicated than precedence.) Some of the operation
definition functions take additional arguments; see the function
descriptions for details.

prefix'
rbp=180

postfix'
lbp=180

infix'
lbp=180, rbp=180

nary'
lbp=180, rbp=180

matchfix'
(binding power not applicable)

nofix'
(binding power not applicable)

For comparison, here are some built-in operators and their left and
right binding powers.

Operator   lbp     rbp

:        180     20
::       180     20
:=       180     20
::=      180     20
!        160
!!       160
^        140     139
.        130     129
*        120
/        120     120
+        100     100
-        100     134
=        80      80
#        80      80
>        80      80
>=       80      80
<        80      80
<=       80      80
not              70
and      65
or       60
,        10
$-1 ; -1 remove' and kill' remove operator properties from an atom. remove ("<a>", op)' removes only the operator properties of <a>. kill ("<a>")' removes all properties of <a>, including the operator properties. Note that the name of the operator must be enclosed in quotation marks. (%i1) infix ("##"); (%o1) ## (%i2) "##" (a, b) := a^b; b (%o2) a ## b := a (%i3) 5 ## 3; (%o3) 125 (%i4) remove ("##", op); (%o4) done (%i5) 5 ## 3; Incorrect syntax: # is not a prefix operator 5 ## ^ (%i5) "##" (5, 3); (%o5) 125 (%i6) infix ("##"); (%o6) ## (%i7) 5 ## 3; (%o7) 125 (%i8) kill ("##"); (%o8) done (%i9) 5 ## 3; Incorrect syntax: # is not a prefix operator 5 ## ^ (%i9) "##" (5, 3); (%o9) ##(5, 3)  ## 7.2 Arithmetic operators Operator: +  Operator: -  Operator: *  Operator: /  Operator: ^   The symbols +' *' /' and ^' represent addition, multiplication, division, and exponentiation, respectively. The names of these operators are "+"' "*"' "/"' and "^"', which may appear where the name of a function or operator is required. The symbols +' and -' represent unary addition and negation, respectively, and the names of these operators are "+"' and "-"', respectively. Subtraction a - b' is represented within Maxima as addition, a + (- b)'. Expressions such as a + (- b)' are displayed as subtraction. Maxima recognizes "-"' only as the name of the unary negation operator, and not as the name of the binary subtraction operator. Division a / b' is represented within Maxima as multiplication, a * b^(- 1)'. Expressions such as a * b^(- 1)' are displayed as division. Maxima recognizes "/"' as the name of the division operator. Addition and multiplication are n-ary, commutative operators. Division and exponentiation are binary, noncommutative operators. Maxima sorts the operands of commutative operators to construct a canonical representation. For internal storage, the ordering is determined by orderlessp'. For display, the ordering for addition is determined by ordergreatp', and for multiplication, it is the same as the internal ordering. Arithmetic computations are carried out on literal numbers (integers, rationals, ordinary floats, and bigfloats). Except for exponentiation, all arithmetic operations on numbers are simplified to numbers. Exponentiation is simplified to a number if either operand is an ordinary float or bigfloat or if the result is an exact integer or rational; otherwise an exponentiation may be simplified to sqrt' or another exponentiation or left unchanged. Floating-point contagion applies to arithmetic computations: if any operand is a bigfloat, the result is a bigfloat; otherwise, if any operand is an ordinary float, the result is an ordinary float; otherwise, the operands are rationals or integers and the result is a rational or integer. Arithmetic computations are a simplification, not an evaluation. Thus arithmetic is carried out in quoted (but simplified) expressions. Arithmetic operations are applied element-by-element to lists when the global flag listarith' is true', and always applied element-by-element to matrices. When one operand is a list or matrix and another is an operand of some other type, the other operand is combined with each of the elements of the list or matrix. Examples: Addition and multiplication are n-ary, commutative operators. Maxima sorts the operands to construct a canonical representation. The names of these operators are "+"' and "*"'. (%i1) c + g + d + a + b + e + f; (%o1) g + f + e + d + c + b + a (%i2) [op (%), args (%)]; (%o2) [+, [g, f, e, d, c, b, a]] (%i3) c * g * d * a * b * e * f; (%o3) a b c d e f g (%i4) [op (%), args (%)]; (%o4) [*, [a, b, c, d, e, f, g]] (%i5) apply ("+", [a, 8, x, 2, 9, x, x, a]); (%o5) 3 x + 2 a + 19 (%i6) apply ("*", [a, 8, x, 2, 9, x, x, a]); 2 3 (%o6) 144 a x Division and exponentiation are binary, noncommutative operators. The names of these operators are "/"' and "^"'. (%i1) [a / b, a ^ b]; a b (%o1) [-, a ] b (%i2) [map (op, %), map (args, %)]; (%o2) [[/, ^], [[a, b], [a, b]]] (%i3) [apply ("/", [a, b]), apply ("^", [a, b])]; a b (%o3) [-, a ] b Subtraction and division are represented internally in terms of addition and multiplication, respectively. (%i1) [inpart (a - b, 0), inpart (a - b, 1), inpart (a - b, 2)]; (%o1) [+, a, - b] (%i2) [inpart (a / b, 0), inpart (a / b, 1), inpart (a / b, 2)]; 1 (%o2) [*, a, -] b Computations are carried out on literal numbers. Floating-point contagion applies. (%i1) 17 + b - (1/2)*29 + 11^(2/4); 5 (%o1) b + sqrt(11) + - 2 (%i2) [17 + 29, 17 + 29.0, 17 + 29b0]; (%o2) [46, 46.0, 4.6b1] Arithmetic computations are a simplification, not an evaluation. (%i1) simp : false; (%o1) false (%i2) '(17 + 29*11/7 - 5^3); 29 11 3 (%o2) 17 + ----- - 5 7 (%i3) simp : true; (%o3) true (%i4) '(17 + 29*11/7 - 5^3); 437 (%o4) - --- 7 Arithmetic is carried out element-by-element for lists (depending on listarith') and matrices. (%i1) matrix ([a, x], [h, u]) - matrix ([1, 2], [3, 4]); [ a - 1 x - 2 ] (%o1) [ ] [ h - 3 u - 4 ] (%i2) 5 * matrix ([a, x], [h, u]); [ 5 a 5 x ] (%o2) [ ] [ 5 h 5 u ] (%i3) listarith : false; (%o3) false (%i4) [a, c, m, t] / [1, 7, 2, 9]; [a, c, m, t] (%o4) ------------ [1, 7, 2, 9] (%i5) [a, c, m, t] ^ x; x (%o5) [a, c, m, t] (%i6) listarith : true; (%o6) true (%i7) [a, c, m, t] / [1, 7, 2, 9]; c m t (%o7) [a, -, -, -] 7 2 9 (%i8) [a, c, m, t] ^ x; x x x x (%o8) [a , c , m , t ]  Operator: **   Exponentiation operator. Maxima recognizes **' as the same operator as ^' in input, and it is displayed as ^' in 1-dimensional output, or by placing the exponent as a superscript in 2-dimensional output. The fortran' function displays the exponentiation operator as **', whether it was input as **' or ^'. Examples: (%i1) is (a**b = a^b); (%o1) true (%i2) x**y + x^z; z y (%o2) x + x (%i3) string (x**y + x^z); (%o3) x^z+x^y (%i4) fortran (x**y + x^z); x**z+x**y (%o4) done  Operator: ^^   Noncommutative exponentiation operator. ^^' is the exponentiation operator corresponding to noncommutative multiplication .', just as the ordinary exponentiation operator ^' corresponds to commutative multiplication *'. Noncommutative exponentiation is displayed by ^^' in 1-dimensional output, and by placing the exponent as a superscript within angle brackets < >' in 2-dimensional output. Examples: (%i1) a . a . b . b . b + a * a * a * b * b; 3 2 <2> <3> (%o1) a b + a . b (%i2) string (a . a . b . b . b + a * a * a * b * b); (%o2) a^3*b^2+a^^2 . b^^3  Operator: .   The dot operator, for matrix (non-commutative) multiplication. When "."' is used in this way, spaces should be left on both sides of it, e.g. A . B'. This distinguishes it plainly from a decimal point in a floating point number. See also dot', dot0nscsimp', dot0simp', dot1simp', dotassoc', dotconstrules', dotdistrib', dotexptsimp', dotident', and dotscrules'.  ## 7.3 Relational operators Operator: <  Operator: <=  Operator: >=  Operator: >   The symbols <' <=' >=' and >' represent less than, less than or equal, greater than or equal, and greater than, respectively. The names of these operators are "<"' "<="' ">="' and ">"', which may appear where the name of a function or operator is required. These relational operators are all binary operators; constructs such as a < b < c' are not recognized by Maxima. Relational expressions are evaluated to Boolean values by the functions is' and maybe', and the programming constructs if', while', and unless'. Relational expressions are not otherwise evaluated or simplified to Boolean values, although the arguments of relational expressions are evaluated (when evaluation is not otherwise prevented by quotation). When a relational expression cannot be evaluated to true' or false', the behavior of is' and if' are governed by the global flag prederror'. When prederror' is true', is' and if' trigger an error. When prederror' is false', is' returns unknown', and if' returns a partially-evaluated conditional expression. maybe' always behaves as if prederror' were false', and while' and unless' always behave as if prederror' were true'. Relational operators do not distribute over lists or other aggregates. See also =', #', equal', and notequal'. Examples: Relational expressions are evaluated to Boolean values by some functions and programming constructs. (%i1) [x, y, z] : [123, 456, 789]; (%o1) [123, 456, 789] (%i2) is (x < y); (%o2) true (%i3) maybe (y > z); (%o3) false (%i4) if x >= z then 1 else 0; (%o4) 0 (%i5) block ([S], S : 0, for i:1 while i <= 100 do S : S + i, return (S)); (%o5) 5050 Relational expressions are not otherwise evaluated or simplified to Boolean values, although the arguments of relational expressions are evaluated. (%o1) [123, 456, 789] (%i2) [x < y, y <= z, z >= y, y > z]; (%o2) [123 < 456, 456 <= 789, 789 >= 456, 456 > 789] (%i3) map (is, %); (%o3) [true, true, true, false]  ## 7.4 Logical operators Operator: and   The logical conjunction operator. and' is an n-ary infix operator; its operands are Boolean expressions, and its result is a Boolean value. and' forces evaluation (like is') of one or more operands, and may force evaluation of all operands. Operands are evaluated in the order in which they appear. and' evaluates only as many of its operands as necessary to determine the result. If any operand is false', the result is false' and no further operands are evaluated. The global flag prederror' governs the behavior of and' when an evaluated operand cannot be determined to be true' or false'. and' prints an error message when prederror' is true'. Otherwise, operands which do not evaluate to true' or false' are accepted, and the result is a Boolean expression. and' is not commutative: a and b' might not be equal to b and a' due to the treatment of indeterminate operands.  Operator: not   The logical negation operator. not' is a prefix operator; its operand is a Boolean expression, and its result is a Boolean value. not' forces evaluation (like is') of its operand. The global flag prederror' governs the behavior of not' when its operand cannot be determined to be true' or false'. not' prints an error message when prederror' is true'. Otherwise, operands which do not evaluate to true' or false' are accepted, and the result is a Boolean expression.  Operator: or   The logical disjunction operator. or' is an n-ary infix operator; its operands are Boolean expressions, and its result is a Boolean value. or' forces evaluation (like is') of one or more operands, and may force evaluation of all operands. Operands are evaluated in the order in which they appear. or' evaluates only as many of its operands as necessary to determine the result. If any operand is true', the result is true' and no further operands are evaluated. The global flag prederror' governs the behavior of or' when an evaluated operand cannot be determined to be true' or false'. or' prints an error message when prederror' is true'. Otherwise, operands which do not evaluate to true' or false' are accepted, and the result is a Boolean expression. or' is not commutative: a or b' might not be equal to b or a' due to the treatment of indeterminate operands.  ## 7.5 Operators for Equations Operator: #   Represents the negation of syntactic equality ='. Note that because of the rules for evaluation of predicate expressions (in particular because not <expr>' causes evaluation of <expr>), not <a> = <b>' is equivalent to is(<a> # <b>)', instead of <a> # <b>'. Examples: (%i1) a = b; (%o1) a = b (%i2) is (a = b); (%o2) false (%i3) a # b; (%o3) a # b (%i4) not a = b; (%o4) true (%i5) is (a # b); (%o5) true (%i6) is (not a = b); (%o6) true  Operator: =   The equation operator. An expression <a> = <b>', by itself, represents an unevaluated equation, which might or might not hold. Unevaluated equations may appear as arguments to solve' and algsys' or some other functions. The function is' evaluates =' to a Boolean value. is(<a> = <b>)' evaluates <a> = <b>' to true' when <a> and <b> are identical. That is, <a> and <b> are atoms which are identical, or they are not atoms and their operators are identical and their arguments are identical. Otherwise, is(<a> = <b>)' evaluates to false'; it never evaluates to unknown'. When is(<a> = <b>)' is true', <a> and <b> are said to be syntactically equal, in contrast to equivalent expressions, for which is(equal(<a>, <b>))' is true'. Expressions can be equivalent and not syntactically equal. The negation of =' is represented by #'. As with =', an expression <a> # <b>', by itself, is not evaluated. is(<a> # <b>)' evaluates <a> # <b>' to true' or false'. In addition to is', some other operators evaluate =' and #' to true' or false', namely if', and', or', and not'. Note that because of the rules for evaluation of predicate expressions (in particular because not <expr>' causes evaluation of <expr>), not <a> = <b>' is equivalent to is(<a> # <b>)', instead of <a> # <b>'. rhs' and lhs' return the right-hand and left-hand sides, respectively, of an equation or inequation. See also equal' and notequal'. Examples: An expression <a> = <b>', by itself, represents an unevaluated equation, which might or might not hold. (%i1) eq_1 : a * x - 5 * y = 17; (%o1) a x - 5 y = 17 (%i2) eq_2 : b * x + 3 * y = 29; (%o2) 3 y + b x = 29 (%i3) solve ([eq_1, eq_2], [x, y]); 196 29 a - 17 b (%o3) [[x = ---------, y = -----------]] 5 b + 3 a 5 b + 3 a (%i4) subst (%, [eq_1, eq_2]); 196 a 5 (29 a - 17 b) (%o4) [--------- - --------------- = 17, 5 b + 3 a 5 b + 3 a 196 b 3 (29 a - 17 b) --------- + --------------- = 29] 5 b + 3 a 5 b + 3 a (%i5) ratsimp (%); (%o5) [17 = 17, 29 = 29] is(<a> = <b>)' evaluates <a> = <b>' to true' when <a> and <b> are syntactically equal (that is, identical). Expressions can be equivalent and not syntactically equal. (%i1) a : (x + 1) * (x - 1); (%o1) (x - 1) (x + 1) (%i2) b : x^2 - 1; 2 (%o2) x - 1 (%i3) [is (a = b), is (a # b)]; (%o3) [false, true] (%i4) [is (equal (a, b)), is (notequal (a, b))]; (%o4) [true, false] Some operators evaluate =' and #' to true' or false'. (%i1) if expand ((x + y)^2) = x^2 + 2 * x * y + y^2 then FOO else BAR; (%o1) FOO (%i2) eq_3 : 2 * x = 3 * x; (%o2) 2 x = 3 x (%i3) eq_4 : exp (2) = %e^2; 2 2 (%o3) %e = %e (%i4) [eq_3 and eq_4, eq_3 or eq_4, not eq_3]; (%o4) [false, true, true] Because not <expr>' causes evaluation of <expr>, not <a> = <b>' is equivalent to is(<a> # <b>)'. (%i1) [2 * x # 3 * x, not (2 * x = 3 * x)]; (%o1) [2 x # 3 x, true] (%i2) is (2 * x # 3 * x); (%o2) true  ## 7.6 Assignment operators Operator: :   Assignment operator. When the left-hand side is a simple variable (not subscripted), :' evaluates its right-hand side and associates that value with the left-hand side. When the left-hand side is a subscripted element of a list, matrix, declared Maxima array, or Lisp array, the right-hand side is assigned to that element. The subscript must name an existing element; such objects cannot be extended by naming nonexistent elements. When the left-hand side is a subscripted element of an undeclared Maxima array, the right-hand side is assigned to that element, if it already exists, or a new element is allocated, if it does not already exist. When the left-hand side is a list of simple and/or subscripted variables, the right-hand side must evaluate to a list, and the elements of the right-hand side are assigned to the elements of the left-hand side, in parallel. See also kill' and remvalue', which undo the association between the left-hand side and its value. Examples: Assignment to a simple variable. (%i1) a; (%o1) a (%i2) a : 123; (%o2) 123 (%i3) a; (%o3) 123 Assignment to an element of a list. (%i1) b : [1, 2, 3]; (%o1) [1, 2, 3] (%i2) b : 456; (%o2) 456 (%i3) b; (%o3) [1, 2, 456] Assignment creates an undeclared array. (%i1) c : 789; (%o1) 789 (%i2) c; (%o2) 789 (%i3) c; (%o3) c (%i4) arrayinfo (c); (%o4) [hashed, 1, ] (%i5) listarray (c); (%o5)  Multiple assignment. (%i1) [a, b, c] : [45, 67, 89]; (%o1) [45, 67, 89] (%i2) a; (%o2) 45 (%i3) b; (%o3) 67 (%i4) c; (%o4) 89 Multiple assignment is carried out in parallel. The values of a' and b' are exchanged in this example. (%i1) [a, b] : [33, 55]; (%o1) [33, 55] (%i2) [a, b] : [b, a]; (%o2) [55, 33] (%i3) a; (%o3) 55 (%i4) b; (%o4) 33  Operator: ::   Assignment operator. ::' is the same as :' (which see) except that ::' evaluates its left-hand side as well as its right-hand side. Examples: (%i1) x : 'foo; (%o1) foo (%i2) x :: 123; (%o2) 123 (%i3) foo; (%o3) 123 (%i4) x : '[a, b, c]; (%o4) [a, b, c] (%i5) x :: [11, 22, 33]; (%o5) [11, 22, 33] (%i6) a; (%o6) 11 (%i7) b; (%o7) 22 (%i8) c; (%o8) 33  Operator: ::=   Macro function definition operator. ::=' defines a function (called a "macro" for historical reasons) which quotes its arguments, and the expression which it returns (called the "macro expansion") is evaluated in the context from which the macro was called. A macro function is otherwise the same as an ordinary function. macroexpand' returns a macro expansion (without evaluating it). macroexpand (foo (x))' followed by ''%' is equivalent to foo (x)' when foo' is a macro function. ::=' puts the name of the new macro function onto the global list macros'. kill', remove', and remfunction' unbind macro function definitions and remove names from macros'. fundef' or dispfun' return a macro function definition or assign it to a label, respectively. Macro functions commonly contain buildq' and splice' expressions to construct an expression, which is then evaluated. Examples A macro function quotes its arguments, so message (1) shows y - z', not the value of y - z'. The macro expansion (the quoted expression '(print ("(2) x is equal to", x))') is evaluated in the context from which the macro was called, printing message (2). (%i1) x: %pi$
(%i2) y: 1234$(%i3) z: 1729 * w$
(%i4) printq1 (x) ::= block (print ("(1) x is equal to", x),
'(print ("(2) x is equal to", x)))$(%i5) printq1 (y - z); (1) x is equal to y - z (2) x is equal to %pi (%o5) %pi An ordinary function evaluates its arguments, so message (1) shows the value of y - z'. The return value is not evaluated, so message (2) is not printed until the explicit evaluation ''%'. (%i1) x: %pi$
(%i2) y: 1234$(%i3) z: 1729 * w$
(%i4) printe1 (x) := block (print ("(1) x is equal to", x),
'(print ("(2) x is equal to", x)))$(%i5) printe1 (y - z); (1) x is equal to 1234 - 1729 w (%o5) print((2) x is equal to, x) (%i6) ''%; (2) x is equal to %pi (%o6) %pi macroexpand' returns a macro expansion. macroexpand (foo (x))' followed by ''%' is equivalent to foo (x)' when foo' is a macro function. (%i1) x: %pi$
(%i2) y: 1234$(%i3) z: 1729 * w$
(%i4) g (x) ::= buildq ([x], print ("x is equal to", x))$(%i5) macroexpand (g (y - z)); (%o5) print(x is equal to, y - z) (%i6) ''%; x is equal to 1234 - 1729 w (%o6) 1234 - 1729 w (%i7) g (y - z); x is equal to 1234 - 1729 w (%o7) 1234 - 1729 w  Operator: :=   The function definition operator. <f>(<x_1>, ..., <x_n>) := <expr>' defines a function named <f> with arguments <x_1>, ..., <x_n> and function body <expr>. :=' never evaluates the function body (unless explicitly evaluated by quote-quote '''). The function body is evaluated every time the function is called. <f>[<x_1>, ..., <x_n>] := <expr>' defines a so-called array function. Its function body is evaluated just once for each distinct value of its arguments, and that value is returned, without evaluating the function body, whenever the arguments have those values again. (A function of this kind is commonly known as a "memoizing function".) <f>[<x_1>, ..., <x_n>](<y_1>, ..., <y_m>) := <expr>' is a special case of an array function. <f>[<x_1>, ..., <x_n>]' is an array function which returns a lambda expression with arguments <y_1>, ..., <y_m>'. The function body is evaluated once for each distinct value of <x_1>, ..., <x_n>', and the body of the lambda expression is that value. When the last or only function argument <x_n> is a list of one element, the function defined by :=' accepts a variable number of arguments. Actual arguments are assigned one-to-one to formal arguments <x_1>, ..., <x_(n - 1)>, and any further actual arguments, if present, are assigned to <x_n> as a list. All function definitions appear in the same namespace; defining a function f' within another function g' does not automatically limit the scope of f' to g'. However, local(f)' makes the definition of function f' effective only within the block or other compound expression in which local' appears. If some formal argument <x_k> is a quoted symbol, the function defined by :=' does not evaluate the corresponding actual argument. Otherwise all actual arguments are evaluated. See also define' and ::='. Examples: :=' never evaluates the function body (unless explicitly evaluated by quote-quote). (%i1) expr : cos(y) - sin(x); (%o1) cos(y) - sin(x) (%i2) F1 (x, y) := expr; (%o2) F1(x, y) := expr (%i3) F1 (a, b); (%o3) cos(y) - sin(x) (%i4) F2 (x, y) := ''expr; (%o4) F2(x, y) := cos(y) - sin(x) (%i5) F2 (a, b); (%o5) cos(b) - sin(a) f(<x_1>, ..., <x_n>) := ...' defines an ordinary function. (%i1) G1(x, y) := (print ("Evaluating G1 for x=", x, "and y=", y), x.y - y.x); (%o1) G1(x, y) := (print("Evaluating G1 for x=", x, "and y=", y), x . y - y . x) (%i2) G1([1, a], [2, b]); Evaluating G1 for x= [1, a] and y= [2, b] (%o2) 0 (%i3) G1([1, a], [2, b]); Evaluating G1 for x= [1, a] and y= [2, b] (%o3) 0 f[<x_1>, ..., <x_n>] := ...' defines an array function. (%i1) G2[a] := (print ("Evaluating G2 for a=", a), a^2); 2 (%o1) G2 := (print("Evaluating G2 for a=", a), a ) a (%i2) G2; Evaluating G2 for a= 1234 (%o2) 1522756 (%i3) G2; (%o3) 1522756 (%i4) G2; Evaluating G2 for a= 2345 (%o4) 5499025 (%i5) arrayinfo (G2); (%o5) [hashed, 1, , ] (%i6) listarray (G2); (%o6) [1522756, 5499025] <f>[<x_1>, ..., <x_n>](<y_1>, ..., <y_m>) := <expr>' is a special case of an array function. (%i1) G3[n](x) := (print ("Evaluating G3 for n=", n), diff (sin(x)^2, x, n)); (%o1) G3 (x) := (print("Evaluating G3 for n=", n), n 2 diff(sin (x), x, n)) (%i2) G3; Evaluating G3 for n= 2 2 2 (%o2) lambda([x], 2 cos (x) - 2 sin (x)) (%i3) G3; 2 2 (%o3) lambda([x], 2 cos (x) - 2 sin (x)) (%i4) G3(1); 2 2 (%o4) 2 cos (1) - 2 sin (1) (%i5) arrayinfo (G3); (%o5) [hashed, 1, ] (%i6) listarray (G3); 2 2 (%o6) [lambda([x], 2 cos (x) - 2 sin (x))] When the last or only function argument <x_n> is a list of one element, the function defined by :=' accepts a variable number of arguments. (%i1) H ([L]) := apply ("+", L); (%o1) H([L]) := apply("+", L) (%i2) H (a, b, c); (%o2) c + b + a local' makes a local function definition. (%i1) foo (x) := 1 - x; (%o1) foo(x) := 1 - x (%i2) foo (100); (%o2) - 99 (%i3) block (local (foo), foo (x) := 2 * x, foo (100)); (%o3) 200 (%i4) foo (100); (%o4) - 99  ## 7.7 User defined operators Function: infix   infix (<op>) infix (<op>, <lbp>, <rbp>) infix (<op>, <lbp>, <rbp>, <lpos>, <rpos>, <pos>) Declares <op> to be an infix operator. An infix operator is a function of two arguments, with the name of the function written between the arguments. For example, the subtraction operator -' is an infix operator. infix (<op>)' declares <op> to be an infix operator with default binding powers (left and right both equal to 180) and parts of speech (left and right both equal to any'). infix (<op>, <lbp>, <rbp>)' declares <op> to be an infix operator with stated left and right binding powers and default parts of speech (left and right both equal to any'). infix (<op>, <lbp>, <rbp>, <lpos>, <rpos>, <pos>)' declares <op> to be an infix operator with stated left and right binding powers and parts of speech <lpos>, <rpos>, and <pos> for the left operand, the right operand, and the operator result, respectively. "Part of speech", in reference to operator declarations, means expression type. Three types are recognized: expr', clause', and any', indicating an algebraic expression, a Boolean expression, or any kind of expression, respectively. Maxima can detect some syntax errors by comparing the declared part of speech to an actual expression. The precedence of <op> with respect to other operators derives from the left and right binding powers of the operators in question. If the left and right binding powers of <op> are both greater the left and right binding powers of some other operator, then <op> takes precedence over the other operator. If the binding powers are not both greater or less, some more complicated relation holds. The associativity of <op> depends on its binding powers. Greater left binding power (<lbp>) implies an instance of <op> is evaluated before other operators to its left in an expression, while greater right binding power (<rbp>) implies an instance of <op> is evaluated before other operators to its right in an expression. Thus greater <lbp> makes <op> right-associative, while greater <rbp> makes <op> left-associative. If <lbp> is equal to <rbp>, <op> is left-associative. See also *note Introduction to operators::. Examples: If the left and right binding powers of <op> are both greater the left and right binding powers of some other operator, then <op> takes precedence over the other operator. (%i1) :lisp (get '$+ 'lbp)
100
(%i1) :lisp (get '$+ 'rbp) 100 (%i1) infix ("##", 101, 101); (%o1) ## (%i2) "##"(a, b) := sconcat("(", a, ",", b, ")"); (%o2) (a ## b) := sconcat("(", a, ",", b, ")") (%i3) 1 + a ## b + 2; (%o3) (a,b) + 3 (%i4) infix ("##", 99, 99); (%o4) ## (%i5) 1 + a ## b + 2; (%o5) (a+1,b+2) Greater <lbp> makes <op> right-associative, while greater <rbp> makes <op> left-associative. (%i1) infix ("##", 100, 99); (%o1) ## (%i2) "##"(a, b) := sconcat("(", a, ",", b, ")")$
(%i3) foo ## bar ## baz;
(%o3)                    (foo,(bar,baz))
(%i4) infix ("##", 100, 101);
(%o4)                          ##
(%i5) foo ## bar ## baz;
(%o5)                    ((foo,bar),baz)

Maxima can detect some syntax errors by comparing the declared
part of speech to an actual expression.

(%i1) infix ("##", 100, 99, expr, expr, expr);
(%o1)                          ##
(%i2) if x ## y then 1 else 0;
Incorrect syntax: Found algebraic expression where logical
expression expected
if x ## y then
^
(%i2) infix ("##", 100, 99, expr, expr, clause);
(%o2)                          ##
(%i3) if x ## y then 1 else 0;
(%o3)                if x ## y then 1 else 0


Function: matchfix

          matchfix (<ldelimiter>, <rdelimiter>)
matchfix (<ldelimiter>, <rdelimiter>, <arg_pos>, <pos>)
Declares a matchfix operator with left and right delimiters
<ldelimiter> and <rdelimiter>.  The delimiters are specified as
strings.

A "matchfix" operator is a function of any number of arguments,
such that the arguments occur between matching left and right
delimiters.  The delimiters may be any strings, so long as the
parser can distinguish the delimiters from the operands and other
expressions and operators.  In practice this rules out unparseable
(%i6) -3*x + 2*y = -4$(%i7) solve ([%o5, %o6]); Solution 1 (%t7) y = - - 5 6 (%t8) x = - 5 (%o8) [[%t7, %t8]] (%i8) %o6, %o8; (%o8) - 4 = - 4 (%i9) x + 1/x > gamma (1/2); 1 (%o9) x + - > sqrt(%pi) x (%i10) %, numer, x=1/2; (%o10) 2.5 > 1.772453850905516 (%i11) %, pred; (%o11) true  Special symbol: eval   As an argument in a call to ev (<expr>)', eval' causes an extra evaluation of <expr>. See ev'. Example: (%i1) [a:b,b:c,c:d,d:e]; (%o1) [b, c, d, e] (%i2) a; (%o2) b (%i3) ev(a); (%o3) c (%i4) ev(a),eval; (%o4) e (%i5) a,eval,eval; (%o5) e  Property: evflag   When a symbol <x> has the evflag' property, the expressions ev(<expr>, <x>)' and <expr>, <x>' (at the interactive prompt) are equivalent to ev(<expr>, <x> = true)'. That is, <x> is bound to true' while <expr> is evaluated. The expression declare(<x>, evflag)' gives the evflag' property to the variable <x>. The flags which have the evflag' property by default are the following: algebraic cauchysum demoivre dotscrules %emode %enumer exponentialize exptisolate factorflag float halfangles infeval isolate_wrt_times keepfloat letrat listarith logabs logarc logexpand lognegint m1pbranch numer_pbranch programmode radexpand ratalgdenom ratfac ratmx ratsimpexpons simp simpproduct simpsum sumexpand trigexpand Examples: (%i1) sin (1/2); 1 (%o1) sin(-) 2 (%i2) sin (1/2), float; (%o2) 0.479425538604203 (%i3) sin (1/2), float=true; (%o3) 0.479425538604203 (%i4) simp : false; (%o4) false (%i5) 1 + 1; (%o5) 1 + 1 (%i6) 1 + 1, simp; (%o6) 2 (%i7) simp : true; (%o7) true (%i8) sum (1/k^2, k, 1, inf); inf ==== \ 1 (%o8) > -- / 2 ==== k k = 1 (%i9) sum (1/k^2, k, 1, inf), simpsum; 2 %pi (%o9) ---- 6 (%i10) declare (aa, evflag); (%o10) done (%i11) if aa = true then YES else NO; (%o11) NO (%i12) if aa = true then YES else NO, aa; (%o12) YES  Property: evfun   When a function <F> has the evfun' property, the expressions ev(<expr>, <F>)' and <expr>, <F>' (at the interactive prompt) are equivalent to <F>(ev(<expr>))'. If two or more evfun' functions <F>, <G>, etc., are specified, the functions are applied in the order that they are specified. The expression declare(<F>, evfun)' gives the evfun' property to the function <F>. The functions which have the evfun' property by default are the following: bfloat factor fullratsimp logcontract polarform radcan ratexpand ratsimp rectform rootscontract trigexpand trigreduce Examples: (%i1) x^3 - 1; 3 (%o1) x - 1 (%i2) x^3 - 1, factor; 2 (%o2) (x - 1) (x + x + 1) (%i3) factor (x^3 - 1); 2 (%o3) (x - 1) (x + x + 1) (%i4) cos(4 * x) / sin(x)^4; cos(4 x) (%o4) -------- 4 sin (x) (%i5) cos(4 * x) / sin(x)^4, trigexpand; 4 2 2 4 sin (x) - 6 cos (x) sin (x) + cos (x) (%o5) ------------------------------------- 4 sin (x) (%i6) cos(4 * x) / sin(x)^4, trigexpand, ratexpand; 2 4 6 cos (x) cos (x) (%o6) - --------- + ------- + 1 2 4 sin (x) sin (x) (%i7) ratexpand (trigexpand (cos(4 * x) / sin(x)^4)); 2 4 6 cos (x) cos (x) (%o7) - --------- + ------- + 1 2 4 sin (x) sin (x) (%i8) declare ([F, G], evfun); (%o8) done (%i9) (aa : bb, bb : cc, cc : dd); (%o9) dd (%i10) aa; (%o10) bb (%i11) aa, F; (%o11) F(cc) (%i12) F (aa); (%o12) F(bb) (%i13) F (ev (aa)); (%o13) F(cc) (%i14) aa, F, G; (%o14) G(F(cc)) (%i15) G (F (ev (aa))); (%o15) G(F(cc))  Option variable: infeval   Enables "infinite evaluation" mode. ev' repeatedly evaluates an expression until it stops changing. To prevent a variable, say X', from being evaluated away in this mode, simply include X='X' as an argument to ev'. Of course expressions such as ev (X, X=X+1, infeval)' will generate an infinite loop.  Special symbol: noeval   noeval' suppresses the evaluation phase of ev'. This is useful in conjunction with other switches and in causing expressions to be resimplified without being reevaluated.  Special symbol: nouns   nouns' is an evflag'. When used as an option to the ev' command, nouns' converts all "noun" forms occurring in the expression being ev''d to "verbs", i.e., evaluates them. See also noun', nounify', verb', and verbify'.  Special symbol: pred   As an argument in a call to ev (<expr>)', pred' causes predicates (expressions which evaluate to true' or false') to be evaluated. See ev'. Example: (%i1) 1<2; (%o1) 1 < 2 (%i2) 1<2,pred; (%o2) true  ## 9 Simplification  Functions and Variables for Simplification  ## 9.1 Functions and Variables for Simplification Property: additive   If declare(f,additive)' has been executed, then: (1) If f' is univariate, whenever the simplifier encounters f' applied to a sum, f' will be distributed over that sum. I.e. f(y+x)' will simplify to f(y)+f(x)'. (2) If f' is a function of 2 or more arguments, additivity is defined as additivity in the first argument to f', as in the case of sum' or integrate', i.e. f(h(x)+g(x),x)' will simplify to f(h(x),x)+f(g(x),x)'. This simplification does not occur when f' is applied to expressions of the form sum(x[i],i,lower-limit,upper-limit)'. Example: (%i1) F3 (a + b + c); (%o1) F3(c + b + a) (%i2) declare (F3, additive); (%o2) done (%i3) F3 (a + b + c); (%o3) F3(c) + F3(b) + F3(a)  Property: antisymmetric   If declare(h,antisymmetric)' is done, this tells the simplifier that h' is antisymmetric. E.g. h(x,z,y)' will simplify to - h(x, y, z)'. That is, it will give (-1)^n times the result given by symmetric' or commutative', where n is the number of interchanges of two arguments necessary to convert it to that form. Examples: (%i1) S (b, a); (%o1) S(b, a) (%i2) declare (S, symmetric); (%o2) done (%i3) S (b, a); (%o3) S(a, b) (%i4) S (a, c, e, d, b); (%o4) S(a, b, c, d, e) (%i5) T (b, a); (%o5) T(b, a) (%i6) declare (T, antisymmetric); (%o6) done (%i7) T (b, a); (%o7) - T(a, b) (%i8) T (a, c, e, d, b); (%o8) T(a, b, c, d, e)  Function: combine (<expr>)   Simplifies the sum <expr> by combining terms with the same denominator into a single term. Example: (%i1) 1*f/2*b + 2*c/3*a + 3*f/4*b +c/5*b*a; 5 b f a b c 2 a c (%o1) ----- + ----- + ----- 4 5 3 (%i2) combine (%); 75 b f + 4 (3 a b c + 10 a c) (%o2) ----------------------------- 60  Property: commutative   If declare(h, commutative)' is done, this tells the simplifier that h' is a commutative function. E.g. h(x, z, y)' will simplify to h(x, y, z)'. This is the same as symmetric'. Exemplo: (%i1) S (b, a); (%o1) S(b, a) (%i2) S (a, b) + S (b, a); (%o2) S(b, a) + S(a, b) (%i3) declare (S, commutative); (%o3) done (%i4) S (b, a); (%o4) S(a, b) (%i5) S (a, b) + S (b, a); (%o5) 2 S(a, b) (%i6) S (a, c, e, d, b); (%o6) S(a, b, c, d, e)  Function: demoivre (<expr>)  Option variable: demoivre   The function demoivre (expr)' converts one expression without setting the global variable demoivre'. When the variable demoivre' is true', complex exponentials are converted into equivalent expressions in terms of circular functions: exp (a + b*%i)' simplifies to %e^a * (cos(b) + %i*sin(b))' if b' is free of %i'. a' and b' are not expanded. The default value of demoivre' is false'. exponentialize' converts circular and hyperbolic functions to exponential form. demoivre' and exponentialize' cannot both be true at the same time.  Function: distrib (<expr>)   Distributes sums over products. It differs from expand' in that it works at only the top level of an expression, i.e., it doesn't recurse and it is faster than expand'. It differs from multthru' in that it expands all sums at that level. Examples: (%i1) distrib ((a+b) * (c+d)); (%o1) b d + a d + b c + a c (%i2) multthru ((a+b) * (c+d)); (%o2) (b + a) d + (b + a) c (%i3) distrib (1/((a+b) * (c+d))); 1 (%o3) --------------- (b + a) (d + c) (%i4) expand (1/((a+b) * (c+d)), 1, 0); 1 (%o4) --------------------- b d + a d + b c + a c  Option variable: distribute_over   Default value: true' distribute_over' controls the mapping of functions over bags like lists, matrices, and equations. At this time not all Maxima functions have this property. It is possible to look up this property with the command properties'. The mapping of functions is switched off, when setting distribute_over' to the value false'. Examples: The sin' function maps over a list: (%i1) sin([x,1,1.0]); (%o1) [sin(x), sin(1), .8414709848078965] mod' is a function with two arguments which maps over lists. Mapping over nested lists is possible too: (%i2) mod([x,11,2*a],10); (%o2) [mod(x, 10), 1, 2 mod(a, 5)] (%i3) mod([[x,y,z],11,2*a],10); (%o3) [[mod(x, 10), mod(y, 10), mod(z, 10)], 1, 2 mod(a, 5)] Mapping of the floor' function over a matrix and an equation: (%i4) floor(matrix([a,b],[c,d])); [ floor(a) floor(b) ] (%o4) [ ] [ floor(c) floor(d) ] (%i5) floor(a=b); (%o5) floor(a) = floor(b) Functions with more than one argument map over any of the arguments or all arguments: (%i6) expintegral_e([1,2],[x,y]); (%o6) [[expintegral_e(1, x), expintegral_e(1, y)], [expintegral_e(2, x), expintegral_e(2, y)]] Check if a function has the property distribute_over: (%i7) properties(abs); (%o7) [integral, distributes over bags, noun, rule, gradef] The mapping of functions is switched off, when setting distribute_over' to the value false'. (%i1) distribute_over; (%o1) true (%i2) sin([x,1,1.0]); (%o2) [sin(x), sin(1), 0.8414709848078965] (%i3) distribute_over : not distribute_over; (%o3) false (%i4) sin([x,1,1.0]); (%o4) sin([x, 1, 1.0]) (%i5)  Option variable: domain   Default value: real' When domain' is set to complex', sqrt (x^2)' will remain sqrt (x^2)' instead of returning abs(x)'.  Property: evenfun  Property: oddfun   declare(f, evenfun)' or declare(f, oddfun)' tells Maxima to recognize the function f' as an even or odd function. Examples: (%i1) o (- x) + o (x); (%o1) o(x) + o(- x) (%i2) declare (o, oddfun); (%o2) done (%i3) o (- x) + o (x); (%o3) 0 (%i4) e (- x) - e (x); (%o4) e(- x) - e(x) (%i5) declare (e, evenfun); (%o5) done (%i6) e (- x) - e (x); (%o6) 0  Function: expand   expand (<expr>) expand (<expr>, <p>, <n>) Expand expression <expr>. Products of sums and exponentiated sums are multiplied out, numerators of rational expressions which are sums are split into their respective terms, and multiplication (commutative and non-commutative) are distributed over addition at all levels of <expr>. For polynomials one should usually use ratexpand' which uses a more efficient algorithm. maxnegex' and maxposex' control the maximum negative and positive exponents, respectively, which will expand. expand (<expr>, <p>, <n>)' expands <expr>, using <p> for maxposex' and <n> for maxnegex'. This is useful in order to expand part but not all of an expression. expon' - the exponent of the largest negative power which is automatically expanded (independent of calls to expand'). For example if expon' is 4 then (x+1)^(-5)' will not be automatically expanded. expop' - the highest positive exponent which is automatically expanded. Thus (x+1)^3', when typed, will be automatically expanded only if expop' is greater than or equal to 3. If it is desired to have (x+1)^n' expanded where n' is greater than expop' then executing expand ((x+1)^n)' will work only if maxposex' is not less than n'. expand(expr, 0, 0)' causes a resimplification of expr'. expr' is not reevaluated. In distinction from ev(expr, noeval)' a special representation (e. g. a CRE form) is removed. See also ev'. The expand' flag used with ev' causes expansion. The file share/simplification/facexp.mac' contains several related functions (in particular facsum', factorfacsum' and collectterms', which are autoloaded) and variables (nextlayerfactor' and facsum_combine') that provide the user with the ability to structure expressions by controlled expansion. Brief function descriptions are available in simplification/facexp.usg'. A demo is available by doing demo("facexp")'. Examples: (%i1) expr:(x+1)^2*(y+1)^3; 2 3 (%o1) (x + 1) (y + 1) (%i2) expand(expr); 2 3 3 3 2 2 2 2 2 (%o2) x y + 2 x y + y + 3 x y + 6 x y + 3 y + 3 x y 2 + 6 x y + 3 y + x + 2 x + 1 (%i3) expand(expr,2); 2 3 3 3 (%o3) x (y + 1) + 2 x (y + 1) + (y + 1) (%i4) expr:(x+1)^-2*(y+1)^3; 3 (y + 1) (%o4) -------- 2 (x + 1) (%i5) expand(expr); 3 2 y 3 y 3 y 1 (%o5) ------------ + ------------ + ------------ + ------------ 2 2 2 2 x + 2 x + 1 x + 2 x + 1 x + 2 x + 1 x + 2 x + 1 (%i6) expand(expr,2,2); 3 (y + 1) (%o6) ------------ 2 x + 2 x + 1 Resimplify an expression without expansion: (%i7) expr:(1+x)^2*sin(x); 2 (%o7) (x + 1) sin(x) (%i8) exponentialize:true; (%o8) true (%i9) expand(expr,0,0); 2 %i x - %i x %i (x + 1) (%e - %e ) (%o9) - ------------------------------- 2  Function: expandwrt (<expr>, <x_1>, ..., <x_n>)   Expands expression expr' with respect to the variables <x_1>, ..., <x_n>. All products involving the variables appear explicitly. The form returned will be free of products of sums of expressions that are not free of the variables. <x_1>, ..., <x_n> may be variables, operators, or expressions. By default, denominators are not expanded, but this can be controlled by means of the switch expandwrt_denom'. This function is autoloaded from simplification/stopex.mac'.  Option variable: expandwrt_denom   Default value: false' expandwrt_denom' controls the treatment of rational expressions by expandwrt'. If true', then both the numerator and denominator of the expression will be expanded according to the arguments of expandwrt', but if expandwrt_denom' is false', then only the numerator will be expanded in that way.  Function: expandwrt_factored (<expr>, <x_1>, ..., <x_n>)   is similar to expandwrt', but treats expressions that are products somewhat differently. expandwrt_factored' expands only on those factors of expr' that contain the variables <x_1>, ..., <x_n>. This function is autoloaded from simplification/stopex.mac'.  Option variable: expon   Default value: 0 expon' is the exponent of the largest negative power which is automatically expanded (independent of calls to expand'). For example, if expon' is 4 then (x+1)^(-5)' will not be automatically expanded.  Function: exponentialize (<expr>)  Option variable: exponentialize   The function exponentialize (expr)' converts circular and hyperbolic functions in <expr> to exponentials, without setting the global variable exponentialize'. When the variable exponentialize' is true', all circular and hyperbolic functions are converted to exponential form. The default value is false'. demoivre' converts complex exponentials into circular functions. exponentialize' and demoivre' cannot both be true at the same time.  Option variable: expop   Default value: 0 expop' is the highest positive exponent which is automatically expanded. Thus (x + 1)^3', when typed, will be automatically expanded only if expop' is greater than or equal to 3. If it is desired to have (x + 1)^n' expanded where n' is greater than expop' then executing expand ((x + 1)^n)' will work only if maxposex' is not less than n.  Property: lassociative   declare (g, lassociative)' tells the Maxima simplifier that g' is left-associative. E.g., g (g (a, b), g (c, d))' will simplify to g (g (g (a, b), c), d)'.  Property: linear   One of Maxima's operator properties. For univariate f' so declared, "expansion" f(x + y)' yields f(x) + f(y)', f(a*x)' yields a*f(x)' takes place where a' is a "constant". For functions of two or more arguments, "linearity" is defined to be as in the case of sum' or integrate', i.e., f (a*x + b, x)' yields a*f(x,x) + b*f(1,x)' for a' and b' free of x'. Example: (%i1) declare (f, linear); (%o1) done (%i2) f(x+y); (%o2) f(y) + f(x) (%i3) declare (a, constant); (%o3) done (%i4) f(a*x); (%o4) a f(x) linear' is equivalent to additive' and outative'. See also opproperties'. Example: (%i1) 'sum (F(k) + G(k), k, 1, inf); inf ==== \ (%o1) > (G(k) + F(k)) / ==== k = 1 (%i2) declare (nounify (sum), linear); (%o2) done (%i3) 'sum (F(k) + G(k), k, 1, inf); inf inf ==== ==== \ \ (%o3) > G(k) + > F(k) / / ==== ==== k = 1 k = 1  Option variable: maxnegex   Default value: 1000 maxnegex' is the largest negative exponent which will be expanded by the expand' command (see also maxposex').  Option variable: maxposex   Default value: 1000 maxposex' is the largest exponent which will be expanded with the expand' command (see also maxnegex').  Property: multiplicative   declare(f, multiplicative)' tells the Maxima simplifier that f' is multiplicative. 1. If f' is univariate, whenever the simplifier encounters f' applied to a product, f' distributes over that product. E.g., f(x*y)' simplifies to f(x)*f(y)'. This simplification is not applied to expressions of the form f('product(...))'. 2. If f' is a function of 2 or more arguments, multiplicativity is defined as multiplicativity in the first argument to f', e.g., f (g(x) * h(x), x)' simplifies to f (g(x) ,x) * f (h(x), x)'. declare(nounify(product), multiplicative)' tells Maxima to simplify symbolic products. Example: (%i1) F2 (a * b * c); (%o1) F2(a b c) (%i2) declare (F2, multiplicative); (%o2) done (%i3) F2 (a * b * c); (%o3) F2(a) F2(b) F2(c) declare(nounify(product), multiplicative)' tells Maxima to simplify symbolic products. (%i1) product (a[i] * b[i], i, 1, n); n /===\ ! ! (%o1) ! ! a b ! ! i i i = 1 (%i2) declare (nounify (product), multiplicative); (%o2) done (%i3) product (a[i] * b[i], i, 1, n); n n /===\ /===\ ! ! ! ! (%o3) ( ! ! a ) ! ! b ! ! i ! ! i i = 1 i = 1  Function: multthru   multthru (<expr>) multthru (<expr_1>, <expr_2>) Multiplies a factor (which should be a sum) of <expr> by the other factors of <expr>. That is, <expr> is <f_1> <f_2> ... <f_n>' where at least one factor, say <f_i>, is a sum of terms. Each term in that sum is multiplied by the other factors in the product. (Namely all the factors except <f_i>). multthru' does not expand exponentiated sums. This function is the fastest way to distribute products (commutative or noncommutative) over sums. Since quotients are represented as products multthru' can be used to divide sums by products as well. multthru (<expr_1>, <expr_2>)' multiplies each term in <expr_2> (which should be a sum or an equation) by <expr_1>. If <expr_1> is not itself a sum then this form is equivalent to multthru (<expr_1>*<expr_2>)'. (%i1) x/(x-y)^2 - 1/(x-y) - f(x)/(x-y)^3; 1 x f(x) (%o1) - ----- + -------- - -------- x - y 2 3 (x - y) (x - y) (%i2) multthru ((x-y)^3, %); 2 (%o2) - (x - y) + x (x - y) - f(x) (%i3) ratexpand (%); 2 (%o3) - y + x y - f(x) (%i4) ((a+b)^10*s^2 + 2*a*b*s + (a*b)^2)/(a*b*s^2); 10 2 2 2 (b + a) s + 2 a b s + a b (%o4) ------------------------------ 2 a b s (%i5) multthru (%); /* note that this does not expand (b+a)^10 */ 10 2 a b (b + a) (%o5) - + --- + --------- s 2 a b s (%i6) multthru (a.(b+c.(d+e)+f)); (%o6) a . f + a . c . (e + d) + a . b (%i7) expand (a.(b+c.(d+e)+f)); (%o7) a . f + a . c . e + a . c . d + a . b  Property: nary   declare(f, nary)' tells Maxima to recognize the function f' as an n-ary function. The nary' declaration is not the same as calling the nary' function. The sole effect of declare(f, nary)' is to instruct the Maxima simplifier to flatten nested expressions, for example, to simplify foo(x, foo(y, z))' to foo(x, y, z)'. See also declare'. Example: (%i1) H (H (a, b), H (c, H (d, e))); (%o1) H(H(a, b), H(c, H(d, e))) (%i2) declare (H, nary); (%o2) done (%i3) H (H (a, b), H (c, H (d, e))); (%o3) H(a, b, c, d, e)  Option variable: negdistrib   Default value: true' When negdistrib' is true', -1 distributes over an expression. E.g., -(x + y)' becomes - y - x'. Setting it to false' will allow - (x + y)' to be displayed like that. This is sometimes useful but be very careful: like the simp' flag, this is one flag you do not want to set to false' as a matter of course or necessarily for other than local use in your Maxima. Example: (%i1) negdistrib; (%o1) true (%i2) -(x+y); (%o2) - y - x (%i3) negdistrib : not negdistrib ; (%o3) false (%i4) -(x+y); (%o4) - (y + x)  System variable: opproperties   opproperties' is the list of the special operator properties recognized by the Maxima simplifier: Example: (%i1) opproperties; (%o1) [linear, additive, multiplicative, outative, evenfun, oddfun,. commutative, symmetric, antisymmetric, nary, lassociative, rassociative]  Property: outative   declare(f, outative)' tells the Maxima simplifier that constant factors in the argument of f' can be pulled out. 1. If f' is univariate, whenever the simplifier encounters f' applied to a product, that product will be partitioned into factors that are constant and factors that are not and the constant factors will be pulled out. E.g., f(a*x)' will simplify to a*f(x)' where a' is a constant. Non-atomic constant factors will not be pulled out. 2. If f' is a function of 2 or more arguments, outativity is defined as in the case of sum' or integrate', i.e., f (a*g(x), x)' will simplify to a * f(g(x), x)' for a' free of x'. sum', integrate', and limit' are all outative'. Example: (%i1) F1 (100 * x); (%o1) F1(100 x) (%i2) declare (F1, outative); (%o2) done (%i3) F1 (100 * x); (%o3) 100 F1(x) (%i4) declare (zz, constant); (%o4) done (%i5) F1 (zz * y); (%o5) zz F1(y)  Function: radcan (<expr>)   Simplifies <expr>, which can contain logs, exponentials, and radicals, by converting it into a form which is canonical over a large class of expressions and a given ordering of variables; that is, all functionally equivalent forms are mapped into a unique form. For a somewhat larger class of expressions, radcan' produces a regular form. Two equivalent expressions in this class do not necessarily have the same appearance, but their difference can be simplified by radcan' to zero. For some expressions radcan' is quite time consuming. This is the cost of exploring certain relationships among the components of the expression for simplifications based on factoring and partial-fraction expansions of exponents. Examples: (%i1) radcan((log(x+x^2)-log(x))^a/log(1+x)^(a/2)); a/2 (%o1) log(x + 1) (%i2) radcan((log(1+2*a^x+a^(2*x))/log(1+a^x))); (%o2) 2 (%i3) radcan((%e^x-1)/(1+%e^(x/2))); x/2 (%o3) %e - 1  Option variable: radexpand   Default value: true' radexpand' controls some simplifications of radicals. When radexpand' is all', causes nth roots of factors of a product which are powers of n to be pulled outside of the radical. E.g. if radexpand' is all', sqrt (16*x^2)' simplifies to 4*x'. More particularly, consider sqrt (x^2)'. * If radexpand' is all' or assume (x > 0)' has been executed, sqrt(x^2)' simplifies to x'. * If radexpand' is true' and domain' is real' (its default), sqrt(x^2)' simplifies to abs(x)'. * If radexpand' is false', or radexpand' is true' and domain' is complex', sqrt(x^2)' is not simplified. Note that domain' only matters when radexpand' is true'.  Property: rassociative   declare (g, rassociative)' tells the Maxima simplifier that g' is right-associative. E.g., g(g(a, b), g(c, d))' simplifies to g(a, g(b, g(c, d)))'.  Function: scsimp (<expr>, <rule_1>, ..., <rule_n>)   Sequential Comparative Simplification (method due to Stoute). scsimp' attempts to simplify <expr> according to the rules <rule_1>, ..., <rule_n>. If a smaller expression is obtained, the process repeats. Otherwise after all simplifications are tried, it returns the original answer. example (scsimp)' displays some examples.  Option variable: simp   Default value: true' simp' enables simplification. This is the standard. simp' is also an evflag', which is recognized by the function ev'. See ev'. When simp' is used as an evflag' with a value false', the simplification is suppressed only during the evaluation phase of an expression. The flag can not suppress the simplification which follows the evaluation phase. Examples: The simplification is switched off globally. The expression sin(1.0)' is not simplified to its numerical value. The simp'-flag switches the simplification on. (%i1) simp:false; (%o1) false (%i2) sin(1.0); (%o2) sin(1.0) (%i3) sin(1.0),simp; (%o3) .8414709848078965 The simplification is switched on again. The simp'-flag cannot suppress the simplification completely. The output shows a simplified expression, but the variable x' has an unsimplified expression as a value, because the assignment has occurred during the evaluation phase of the expression. (%i4) simp:true; (%o4) true (%i5) x:sin(1.0),simp:false; (%o5) .8414709848078965 (%i6) :lisp$X
((%SIN) 1.0)


Property: symmetric

     declare (h, symmetric)' tells the Maxima simplifier that h' is a
symmetric function.  E.g., h (x, z, y)' simplifies to h (x, y,
z)'.

commutative' is synonymous with symmetric'.


Function: xthru (<expr>)

     Combines all terms of <expr> (which should be a sum) over a common
denominator without expanding products and exponentiated sums as
ratsimp' does.  xthru' cancels common factors in the numerator
and denominator of rational expressions but only if the factors
are explicit.

Sometimes it is better to use xthru' before ratsimp'ing an
expression in order to cause explicit factors of the gcd of the
numerator and denominator to be canceled thus simplifying the
expression to be ratsimp'ed.

Examples:

(%i1) ((x+2)^20 - 2*y)/(x+y)^20 + (x+y)^(-19) - x/(x+y)^20;
20
1       (x + 2)   - 2 y       x
(%o1)        --------- + --------------- - ---------
19             20             20
(y + x)        (y + x)        (y + x)
(%i2) xthru (%);
20
(x + 2)   - y
(%o2)                     -------------
20
(y + x)



## 10 Mathematical Functions


Functions for Numbers
Functions for Complex Numbers
Combinatorial Functions
* Root Exponential and Logarithmic Functions::
Trigonometric Functions
Random Numbers


## 10.1 Functions for Numbers

Function: abs (<z>)

     The abs' function represents the mathematical absolute value
function and works for both numerical and symbolic values. If the
argument, <z>, is a real or complex number, abs' returns the
absolute value of <z>. If possible, symbolic expressions using the
absolute value function are also simplified.

Maxima can differentiate, integrate and calculate limits for
expressions containing abs'. The abs_integrate' package further
extends Maxima's ability to calculate integrals involving the abs
function. See (%i12) in the examples below.

When applied to a list or matrix, abs' automatically distributes
over the terms. Similarly, it distributes over both sides of an
equation. To alter this behaviour, see the variable
distribute_over'.

Examples:

Calculation of abs' for real and complex numbers, including
numerical constants and various infinities. The first example
shows how abs' distributes over the elements of a list.

(%i1) abs([-4, 0, 1, 1+%i]);
(%o1)                  [4, 0, 1, sqrt(2)]

(%i2) abs((1+%i)*(1-%i));
(%o2)                           2
(%i3) abs(%e+%i);
2
(%o3)                    sqrt(%e  + 1)
(%i4) abs([inf, infinity, minf]);
(%o4)                   [inf, inf, inf]

Simplification of expressions containing abs':

(%i5) abs(x^2);
2
(%o5)                          x
(%i6) abs(x^3);
2
(%o6)                       x  abs(x)

(%i7) abs(abs(x));
(%o7)                       abs(x)
(%i8) abs(conjugate(x));
(%o8)                       abs(x)

Integrating and differentiating with the abs' function. Note that
more integrals involving the abs' function can be performed, if
the abs_integrate' package is loaded. The last example shows the
Laplace transform of abs': see laplace'.

(%i9) diff(x*abs(x),x),expand;
(%o9)                       2 abs(x)

(%i10) integrate(abs(x),x);
x abs(x)
(%o10)                       --------
2

(%i11) integrate(x*abs(x),x);
/
[
(%o11)                     I x abs(x) dx
]
/

(%i12) load(abs_integrate)$(%i13) integrate(x*abs(x),x); 2 3 x abs(x) x signum(x) (%o13) --------- - ------------ 2 6 (%i14) integrate(abs(x),x,-2,%pi); 2 %pi (%o14) ---- + 2 2 (%i15) laplace(abs(x),x,s); 1 (%o15) -- 2 s  Function: ceiling (<x>)   When <x> is a real number, return the least integer that is greater than or equal to <x>. If <x> is a constant expression (10 * %pi', for example), ceiling' evaluates <x> using big floating point numbers, and applies ceiling' to the resulting big float. Because ceiling' uses floating point evaluation, it's possible, although unlikely, that ceiling' could return an erroneous value for constant inputs. To guard against errors, the floating point evaluation is done using three values for fpprec'. For non-constant inputs, ceiling' tries to return a simplified value. Here are examples of the simplifications that ceiling' knows about: (%i1) ceiling (ceiling (x)); (%o1) ceiling(x) (%i2) ceiling (floor (x)); (%o2) floor(x) (%i3) declare (n, integer)$
(%i4) [ceiling (n), ceiling (abs (n)), ceiling (max (n, 6))];
(%o4)                [n, abs(n), max(n, 6)]
(%i5) assume (x > 0, x < 1)$(%i6) ceiling (x); (%o6) 1 (%i7) tex (ceiling (a)); $$\left \lceil a \right \rceil$$ (%o7) false The ceiling' function distributes over lists, matrices and equations. See distribute_over'. Finally, for all inputs that are manifestly complex, ceiling' returns a noun form. If the range of a function is a subset of the integers, it can be declared to be integervalued'. Both the ceiling' and floor' functions can use this information; for example: (%i1) declare (f, integervalued)$
(%i2) floor (f(x));
(%o2)                         f(x)
(%i3) ceiling (f(x) - 1);
(%o3)                       f(x) - 1

Example use:

(%i1) unitfrac(r) := block([uf : [], q],
if not(ratnump(r)) then
error("unitfrac: argument must be a rational number"),
while r # 0 do (
uf : cons(q : 1/ceiling(1/r), uf),
r : r - q),
reverse(uf))$(%i2) unitfrac (9/10); 1 1 1 (%o2) [-, -, --] 2 3 15 (%i3) apply ("+", %); 9 (%o3) -- 10 (%i4) unitfrac (-9/10); 1 (%o4) [- 1, --] 10 (%i5) apply ("+", %); 9 (%o5) - -- 10 (%i6) unitfrac (36/37); 1 1 1 1 1 (%o6) [-, -, -, --, ----] 2 3 8 69 6808 (%i7) apply ("+", %); 36 (%o7) -- 37  Function: entier (<x>)   Returns the largest integer less than or equal to <x> where <x> is numeric. fix' (as in fixnum') is a synonym for this, so fix(<x>)' is precisely the same.  Function: floor (<x>)   When <x> is a real number, return the largest integer that is less than or equal to <x>. If <x> is a constant expression (10 * %pi', for example), floor' evaluates <x> using big floating point numbers, and applies floor' to the resulting big float. Because floor' uses floating point evaluation, it's possible, although unlikely, that floor' could return an erroneous value for constant inputs. To guard against errors, the floating point evaluation is done using three values for fpprec'. For non-constant inputs, floor' tries to return a simplified value. Here are examples of the simplifications that floor' knows about: (%i1) floor (ceiling (x)); (%o1) ceiling(x) (%i2) floor (floor (x)); (%o2) floor(x) (%i3) declare (n, integer)$
(%i4) [floor (n), floor (abs (n)), floor (min (n, 6))];
(%o4)                [n, abs(n), min(n, 6)]
(%i5) assume (x > 0, x < 1)$(%i6) floor (x); (%o6) 0 (%i7) tex (floor (a)); $$\left \lfloor a \right \rfloor$$ (%o7) false The floor' function distributes over lists, matrices and equations. See distribute_over'. Finally, for all inputs that are manifestly complex, floor' returns a noun form. If the range of a function is a subset of the integers, it can be declared to be integervalued'. Both the ceiling' and floor' functions can use this information; for example: (%i1) declare (f, integervalued)$
(%i2) floor (f(x));
(%o2)                         f(x)
(%i3) ceiling (f(x) - 1);
(%o3)                       f(x) - 1


Function: fix (<x>)

     A synonym for entier (<x>)'.


Function: lmax (<L>)

     When <L> is a list or a set, return apply ('max, args (<L>))'.
When <L> is not a list or a set, signal an error.  See also lmin'
and max'.


Function: lmin (<L>)

     When <L> is a list or a set, return apply ('min, args (<L>))'.
When <L> is not a list or a set, signal an error.  See also lmax'
and min'.


Function: max (<x_1>, ..., <x_n>)

     Return a simplified value for the maximum of the expressions <x_1>
through <x_n>.  When get (trylevel, maxmin)', is 2 or greater,
max' uses the simplification max (e, -e) --> |e|'.  When get
(trylevel, maxmin)' is 3 or greater, <max> tries to eliminate
expressions that are between two other arguments; for example,
max (x, 2*x, 3*x) --> max (x, 3*x)'.  To set the value of
trylevel' to 2, use put (trylevel, 2, maxmin)'.

See also min' and lmax'.


Function: min (<x_1>, ..., <x_n>)

     Return a simplified value for the minimum of the expressions x_1'
through x_n'.  When get (trylevel, maxmin)', is 2 or greater,
min' uses the simplification min (e, -e) --> -|e|'.  When get
(trylevel, maxmin)' is 3 or greater, min' tries to eliminate
expressions that are between two other arguments; for example,
min (x, 2*x, 3*x) --> min (x, 3*x)'.  To set the value of
trylevel' to 2, use put (trylevel, 2, maxmin)'.

See also max' and lmin'.


Function: round (<x>)

     When <x> is a real number, returns the closest integer to <x>.
Multiples of 1/2 are rounded to the nearest even integer.
Evaluation of <x> is similar to floor' and ceiling'.

The round' function distributes over lists, matrices and
equations.  See distribute_over'.


Function: signum (<x>)

     For either real or complex numbers <x>, the signum function returns
0 if <x> is zero; for a nonzero numeric input <x>, the signum
function returns x/abs(x)'.

For non-numeric inputs, Maxima attempts to determine the sign of
the input.  When the sign is negative, zero, or positive, signum'
returns -1,0, 1, respectively.  For all other values for the sign,
signum' a simplified but equivalent form.  The simplifications
include reflection (signum(-x)' gives -signum(x)') and
multiplicative identity (signum(x*y)' gives signum(x) *
signum(y)').

The signum' function distributes over a list, a matrix, or an
equation.  See distribute_over'.


Function: truncate (<x>)

     When <x> is a real number, return the closest integer to <x> not
greater in absolute value than <x>.  Evaluation of <x> is similar
to floor' and ceiling'.

The truncate' function distributes over lists, matrices and
equations.  See distribute_over'.



## 10.2 Functions for Complex Numbers

Function: cabs (<expr>)

     Calculates the absolute value of an expression representing a
complex number.  Unlike the function abs', the cabs' function
always decomposes its argument into a real and an imaginary part.
If x' and y' represent real variables or expressions, the cabs'
function calculates the absolute value of x + %i*y' as
2    2
sqrt(y  + x )

The cabs' function can use known properties like symmetry
properties of complex functions to help it calculate the absolute
value of an expression.  If such identities exist, they can be
advertised to cabs' using function properties.  The symmetries
that cabs' understands are: mirror symmetry, conjugate function
and complex characteristic.

cabs' is a verb function and is not suitable for symbolic
calculations.  For such calculations (including integration,
differentiation and taking limits of expressions containing
absolute values), use abs'.

The result of cabs' can include the absolute value function,
abs', and the arc tangent, atan2'.

When applied to a list or matrix, cabs' automatically distributes
over the terms.  Similarly, it distributes over both sides of an
equation.

For further ways to compute with complex numbers, see the functions
rectform', realpart', imagpart', carg', conjugate' and
polarform'.

Examples:

Examples with sqrt' and sin'.

(%i1) cabs(sqrt(1+%i*x));
2     1/4
(%o1)                      (x  + 1)
(%i2) cabs(sin(x+%i*y));
2        2         2        2
(%o2)       sqrt(cos (x) sinh (y) + sin (x) cosh (y))

The error function, erf', has mirror symmetry, which is used here
in the calculation of the absolute value with a complex argument:

(%i3) cabs(erf(x+%i*y));
2
(erf(%i y + x) - erf(%i y - x))
(%o3) sqrt(--------------------------------
4
2
(erf(%i y + x) + erf(%i y - x))
- --------------------------------)
4

Maxima knows complex identities for the Bessel functions, which
allow it to compute the absolute value for complex arguments.
Here is an example for bessel_j'.

(%i4) cabs(bessel_j(1,%i));
(%o4)                 abs(bessel_j(1, %i))


Function: carg (<z>)

     Returns the complex argument of <z>.  The complex argument is an
angle theta' in (-%pi, %pi]' such that r exp (theta %i) = <z>'
where r' is the magnitude of <z>.

carg' is a computational function, not a simplifying function.

See also abs' (complex magnitude), polarform', rectform',
realpart', and imagpart'.

Examples:

(%i1) carg (1);
(%o1)                           0
(%i2) carg (1 + %i);
%pi
(%o2)                          ---
4
(%i3) carg (exp (%i));
(%o3)                           1
(%i4) carg (exp (%pi * %i));
(%o4)                          %pi
(%i5) carg (exp (3/2 * %pi * %i));
%pi
(%o5)                         - ---
2
(%i6) carg (17 * exp (2 * %i));
(%o6)                           2


Function: conjugate (<x>)

     Returns the complex conjugate of <x>.

(%i1) declare ([aa, bb], real, cc, complex, ii, imaginary);

(%o1)                         done
(%i2) conjugate (aa + bb*%i);

(%o2)                      aa - %i bb
(%i3) conjugate (cc);

(%o3)                     conjugate(cc)
(%i4) conjugate (ii);

(%o4)                         - ii
(%i5) conjugate (xx + yy);

(%o5)             conjugate(yy) + conjugate(xx)


Function: imagpart (<expr>)

     Returns the imaginary part of the expression <expr>.

imagpart' is a computational function, not a simplifying function.

See also abs', carg', polarform', rectform', and realpart'.

Example:

(%i1) imagpart (a+b*%i);
(%o1)                                  b
(%i2) imagpart (1+sqrt(2)*%i);
(%o2)                               sqrt(2)
(%i3) imagpart (1);
(%o3)                                  0
(%i4) imagpart (sqrt(2)*%i);
(%o4)                               sqrt(2)


Function: polarform (<expr>)

     Returns an expression r %e^(%i theta)' equivalent to <expr>, such
that r' and theta' are purely real.

Example:

(%i1) polarform(a+b*%i);
2    2    %i atan2(b, a)
(%o1)                   sqrt(b  + a ) %e
(%i2) polarform(1+%i);
%i %pi
------
4
(%o2)                          sqrt(2) %e
(%i3) polarform(1+2*%i);
%i atan(2)
(%o3)                        sqrt(5) %e


Function: realpart (<expr>)

     Returns the real part of <expr>.  realpart' and imagpart' will
work on expressions involving trigonometric and hyperbolic
functions, as well as square root, logarithm, and exponentiation.

Example:

(%i1) realpart (a+b*%i);
(%o1)                                  a
(%i2) realpart (1+sqrt(2)*%i);
(%o2)                                  1
(%i3) realpart (sqrt(2)*%i);
(%o3)                                  0
(%i4) realpart (1);
(%o4)                                  1


Function: rectform (<expr>)

     Returns an expression a + b %i' equivalent to <expr>, such that
<a> and <b> are purely real.

Example:

(%i1) rectform(sqrt(2)*%e^(%i*%pi/4));
(%o1)                               %i + 1
(%i2) rectform(sqrt(b^2+a^2)*%e^(%i*atan2(b, a)));
(%o2)                              %i b + a
(%i3) rectform(sqrt(5)*%e^(%i*atan(2)));
(%o3)                              2 %i + 1



## 10.3 Combinatorial Functions

Operator: !!

     The double factorial operator.

For an integer, float, or rational number n', n!!' evaluates to
the product n (n-2) (n-4) (n-6) ... (n - 2 (k-1))' where k' is
equal to entier (n/2)', that is, the largest integer less than or
equal to n/2'.  Note that this definition does not coincide with
other published definitions for arguments which are not integers.

For an even (or odd) integer n', n!!' evaluates to the product of
all the consecutive even (or odd) integers from 2 (or 1) through
n' inclusive.

For an argument n' which is not an integer, float, or rational,
n!!' yields a noun form genfact (n, n/2, 2)'.


Function: binomial (<x>, <y>)

     The binomial coefficient <x>!/(<y>! (<x> - <y>)!)'.  If <x> and
<y> are integers, then the numerical value of the binomial
coefficient is computed.  If <y>, or <x - y>, is an integer, the
binomial coefficient is expressed as a polynomial.

Examples:

(%i1) binomial (11, 7);
(%o1)                          330
(%i2) 11! / 7! / (11 - 7)!;
(%o2)                          330
(%i3) binomial (x, 7);
(x - 6) (x - 5) (x - 4) (x - 3) (x - 2) (x - 1) x
(%o3)   -------------------------------------------------
5040
(%i4) binomial (x + 7, x);
(x + 1) (x + 2) (x + 3) (x + 4) (x + 5) (x + 6) (x + 7)
(%o4) -------------------------------------------------------
5040
(%i5) binomial (11, y);
(%o5)                    binomial(11, y)


Function: factcomb (<expr>)

     Tries to combine the coefficients of factorials in <expr> with the
factorials themselves by converting, for example, (n + 1)*n!'
into (n + 1)!'.

sumsplitfact' if set to false' will cause minfactorial' to be
applied after a factcomb'.

Example:

(%i1) sumsplitfact;
(%o1)                                true
(%i2) (n + 1)*(n + 1)*n!;
2
(%o2)                             (n + 1)  n!
(%i3) factcomb (%);
(%o3)                         (n + 2)! - (n + 1)!
(%i4) sumsplitfact: not sumsplitfact;
(%o4)                                false
(%i5) (n + 1)*(n + 1)*n!;
2
(%o5)                             (n + 1)  n!
(%i6) factcomb (%);
(%o6)                        n (n + 1)! + (n + 1)!


Function: factorial

Operator: !

     Represents the factorial function.  Maxima treats factorial (<x>)'
the same as <x>!'.

For any complex number x', except for negative integers, x!' is
defined as gamma(x+1)'.

For an integer x', x!' simplifies to the product of the integers
from 1 to x' inclusive.  0!' simplifies to 1.  For a real or
complex number in float or bigfloat precision x', x!' simplifies
to the value of gamma (x+1)'.  For x' equal to n/2' where n' is
an odd integer, x!' simplifies to a rational factor times sqrt
(%pi)' (since gamma (1/2)' is equal to sqrt (%pi)').

The option variables factlim' and gammalim' control the numerical
evaluation of factorials for integer and rational arguments.  The
functions minfactorial' and factcomb' simplifies expressions
containing factorials.

The functions gamma', bffac', and cbffac' are varieties of the
gamma function.  bffac' and cbffac' are called internally by
gamma' to evaluate the gamma function for real and complex
numbers in bigfloat precision.

makegamma' substitutes gamma' for factorials and related
functions.

Maxima knows the derivative of the factorial function and the
limits for specific values like negative integers.

The option variable factorial_expand' controls the simplification
of expressions like (n+x)!', where n' is an integer.

The factorial of an integer is simplified to an exact number
unless the operand is greater than factlim'.  The factorial for
real and complex numbers is evaluated in float or bigfloat
precision.

(%i1) factlim:10;
(%o1)                                 10
(%i2) [0!, (7/2)!, 8!, 20!];
105 sqrt(%pi)
(%o2)                   [1, -------------, 40320, 20!]
16
(%i3) [4.77!, (1.0+%i)!];
(%o3)    [81.44668037931197,
.3430658398165454 %i + .6529654964201665]
(%i4) [2.86b0!, (1.0b0+%i)!];
(%o4) [5.046635586910012b0,
3.430658398165454b-1 %i + 6.529654964201667b-1]

The factorial of a known constant, or general expression is not
simplified.  Even so it may be possible to simplify the factorial
after evaluating the operand.

(%i1) [(%i + 1)!, %pi!, %e!, (cos(1) + sin(1))!];
(%o1)      [(%i + 1)!, %pi!, %e!, (sin(1) + cos(1))!]
(%i2) ev (%, numer, %enumer);
(%o2) [.3430658398165454 %i + .6529654964201665,
7.188082728976031,
4.260820476357003, 1.227580202486819]

Factorials are simplified, not evaluated.  Thus x!' may be
replaced even in a quoted expression.

(%i1) '([0!, (7/2)!, 4.77!, 8!, 20!]);
105 sqrt(%pi)
(%o1) [1, -------------, 81.44668037931199, 40320,
16
2432902008176640000]

Maxima knows the derivative of the factorial function.

(%i1) diff(x!,x);
(%o1)                           x! psi (x + 1)
0

The option variable factorial_expand' controls expansion and
simplification of expressions with the factorial function.

(%i1) (n+1)!/n!,factorial_expand:true;
(%o1)                                n + 1


Option variable: factlim

     Default value: -1

factlim' specifies the highest factorial which is automatically
expanded.  If it is -1 then all integers are expanded.


Option variable: factorial_expand

     Default value: false

The option variable factorial_expand' controls the simplification
of expressions like (n+1)!', where n' is an integer.  See
factorial' for an example.


Function: genfact (<x>, <y>, <z>)

     Returns the generalized factorial, defined as x (x-z) (x - 2 z)
... (x - (y - 1) z)'.  Thus, when <x> is an integer, genfact (x,
x, 1) = x!' and genfact (x, x/2, 2) = x!!'.


Function: minfactorial (<expr>)

     Examines <expr> for occurrences of two factorials which differ by
an integer.  minfactorial' then turns one into a polynomial times
the other.

(%i1) n!/(n+2)!;
n!
(%o1)                       --------
(n + 2)!
(%i2) minfactorial (%);
1
(%o2)                    ---------------
(n + 1) (n + 2)


Option variable: sumsplitfact

     Default value: true'

When sumsplitfact' is false', minfactorial' is applied after a
factcomb'.

(%i1) sumsplitfact
(%o1)                                true
(%i2) n!/(2+n)!
n!
(%o2)                              --------
(n + 2)!
(%i3) factcomb(%)
n!
(%o3)                              --------
(n + 2)!
(%i4) sumsplitfact:not sumsplitfact
(%o4)                                false
(%i5) n!/(2+n)!
n!
(%o5)                              --------
(n + 2)!
(%i6) factcomb(%)
1
(%o6)                           ---------------
(n + 1) (n + 2)



## 10.4 Root, Exponential and Logarithmic Functions

Option variable: %e_to_numlog

     Default value: false'

When true', r' some rational number, and x' some expression,
%e^(r*log(x))' will be simplified into x^r' .  It should be noted
that the radcan' command also does this transformation, and more
complicated transformations of this ilk as well.  The logcontract'
command "contracts" expressions containing log'.


Option variable: %emode

     Default value: true'

When %emode' is true', %e^(%pi %i x)' is simplified as follows.

%e^(%pi %i x)' simplifies to cos (%pi x) + %i sin (%pi x)' if
x' is a floating point number, an integer, or a multiple of 1/2,
1/3, 1/4, or 1/6, and then further simplified.

For other numerical x', %e^(%pi %i x)' simplifies to %e^(%pi %i
y)' where y' is x - 2 k' for some integer k' such that abs(y)
< 1'.

When %emode' is false', no special simplification of %e^(%pi %i
x)' is carried out.

(%i1) %emode
(%o1)                                true
(%i2) %e^(%pi*%i*1)
(%o2)                                 - 1
(%i3) %e^(%pi*%i*216/144)
(%o3)                                - %i
(%i4) %e^(%pi*%i*192/144)
sqrt(3) %i   1
(%o4)                          - ---------- - -
2        2
(%i5) %e^(%pi*%i*180/144)
%i         1
(%o5)                         - ------- - -------
sqrt(2)   sqrt(2)
(%i6) %e^(%pi*%i*120/144)
%i   sqrt(3)
(%o6)                            -- - -------
2       2
(%i7) %e^(%pi*%i*121/144)
121 %i %pi
----------
144
(%o7)                            %e


Option variable: %enumer

     Default value: false'

When %enumer' is true', %e' is replaced by its numeric value
2.718...  whenever numer' is true'.

When %enumer' is false', this substitution is carried out only
if the exponent in %e^x' evaluates to a number.

See also ev' and numer'.

(%i1) %enumer
(%o1)                                false
(%i2) numer
(%o2)                                false
(%i3) 2*%e
(%o3)                                2 %e
(%i4) %enumer:not %enumer
(%o4)                                true
(%i5) 2*%e
(%o5)                                2 %e
(%i6) numer:not numer
(%o6)                                true
(%i7) 2*%e
(%o7)                          5.43656365691809
(%i8) 2*%e^1
(%o8)                          5.43656365691809
(%i9) 2*%e^x
x
(%o9)                       2 2.718281828459045


Function: exp (<x>)

     Represents the exponential function.  Instances of exp (<x>)' in
input are simplified to %e^<x>'; exp' does not appear in
simplified expressions.

demoivre' if true' causes %e^(a + b %i)' to simplify to %e^(a
(cos(b) + %i sin(b)))' if b' is free of %i'.  See demoivre'.

%emode', when true', causes %e^(%pi %i x)' to be simplified.
See %emode'.

%enumer', when true' causes %e' to be replaced by 2.718...
whenever numer' is true'.  See %enumer'.

(%i1) demoivre;
(%o1)                                false
(%i2) %e^(a + b*%i);
%i b + a
(%o2)                             %e
(%i3) demoivre: not demoivre;
(%o3)                                true
(%i4) %e^(a + b*%i);
a
(%o4)                      %e  (%i sin(b) + cos(b))


Function: li [<s>] (<z>)

     Represents the polylogarithm function of order <s> and argument
<z>, defined by the infinite series

inf
====   k
\     z
Li (z) =  >    --
s      /      s
====  k
k = 1

li ' is - log (1 - z)'.  li ' and li ' are the
dilogarithm and trilogarithm functions, respectively.

When the order is 1, the polylogarithm simplifies to - log (1 -
z)', which in turn simplifies to a numerical value if <z> is a
real or complex floating point number or the numer' evaluation
flag is present.

When the order is 2 or 3, the polylogarithm simplifies to a
numerical value if <z> is a real floating point number or the
numer' evaluation flag is present.

Examples:

(%i1) assume (x > 0);
(%o1)                        [x > 0]
(%i2) integrate ((log (1 - t)) / t, t, 0, x);
(%o2)                       - li (x)
2
(%i3) li  (7);
(%o3)                        li (7)
2
(%i4) li  (7), numer;
(%o4)        1.24827317833392 - 6.113257021832577 %i
(%i5) li  (7);
(%o5)                        li (7)
3
(%i6) li  (7), numer;
(%o6)        1.24827317833392 - 6.113257021832577 %i
(%i7) L : makelist (i / 4.0, i, 0, 8);
(%o7)   [0.0, 0.25, 0.5, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0]
(%i8) map (lambda ([x], li  (x)), L);
(%o8) [0, .2676526384986274, .5822405249432515,
.9784693966661848, 1.64493407, 2.190177004178597
- .7010261407036192 %i, 2.374395264042415
- 1.273806203464065 %i, 2.448686757245154
- 1.758084846201883 %i, 2.467401098097648
- 2.177586087815347 %i]
(%i9) map (lambda ([x], li  (x)), L);
(%o9) [0, .2584613953442624, 0.537213192678042,
.8444258046482203, 1.2020569, 1.642866878950322
- .07821473130035025 %i, 2.060877505514697
- .2582419849982037 %i, 2.433418896388322
- .4919260182322965 %i, 2.762071904015935
- .7546938285978846 %i]


Function: log (<x>)

     Represents the natural (base e) logarithm of <x>.

Maxima does not have a built-in function for the base 10 logarithm
or other bases. log10(x) := log(x) / log(10)' is a useful
definition.

Simplification and evaluation of logarithms is governed by several
global flags:

logexpand''
causes log(a^b)' to become b*log(a)'. If it is set to
all', log(a*b)' will also simplify to log(a)+log(b)'.  If
it is set to super', then log(a/b)' will also simplify to
log(a)-log(b)' for rational numbers a/b', a#1'.
(log(1/b)', for b' integer, always simplifies.) If it is
set to false', all of these simplifications will be turned
off.

logsimp''
if false' then no simplification of %e' to a power
containing log''s is done.

lognegint''
if true' implements the rule log(-n)' -> log(n)+%i*%pi' for
n' a positive integer.

%e_to_numlog''
when true', r' some rational number, and x' some
expression, the expression %e^(r*log(x))' will be simplified
into x^r'.  It should be noted that the radcan' command
also does this transformation, and more complicated
transformations of this as well. The logcontract' command
"contracts" expressions containing log'.


Option variable: logabs

     Default value: false'

When doing indefinite integration where logs are generated, e.g.
integrate(1/x,x)', the answer is given in terms of log(abs(...))'
if logabs' is true', but in terms of log(...)' if logabs' is
false'.  For definite integration, the logabs:true' setting is
used, because here "evaluation" of the indefinite integral at the
endpoints is often needed.


Option variable: logarc

Function: logarc (<expr>)

     When the global variable logarc' is true', inverse circular and
hyperbolic functions are replaced by equivalent logarithmic
functions.  The default value of logarc' is false'.

The function logarc(<expr>)' carries out that replacement for an
expression <expr> without setting the global variable logarc'.


Option variable: logconcoeffp

     Default value: false'

Controls which coefficients are contracted when using
logcontract'.  It may be set to the name of a predicate function
of one argument.  E.g. if you like to generate SQRTs, you can do
logconcoeffp:'logconfun$logconfun(m):=featurep(m,integer) or ratnump(m)$' .  Then logcontract(1/2*log(x));' will give
log(sqrt(x))'.


Function: logcontract (<expr>)

     Recursively scans the expression <expr>, transforming
subexpressions of the form a1*log(b1) + a2*log(b2) + c' into
log(ratsimp(b1^a1 * b2^a2)) + c'

(%i1) 2*(a*log(x) + 2*a*log(y))$(%i2) logcontract(%); 2 4 (%o2) a log(x y ) The declaration declare(n,integer)' causes logcontract(2*a*n*log(x))' to simplify to a*log(x^(2*n))'. The coefficients that "contract" in this manner are those such as the 2 and the n' here which satisfy featurep(coeff,integer)'. The user can control which coefficients are contracted by setting the option logconcoeffp' to the name of a predicate function of one argument. E.g. if you like to generate SQRTs, you can do logconcoeffp:'logconfun$ logconfun(m):=featurep(m,integer) or
ratnump(m)$' . Then logcontract(1/2*log(x));' will give log(sqrt(x))'.  Option variable: logexpand   Default value: true' If true', that is the default value, causes log(a^b)' to become b*log(a)'. If it is set to all', log(a*b)' will also simplify to log(a)+log(b)'. If it is set to super', then log(a/b)' will also simplify to log(a)-log(b)' for rational numbers a/b', a#1'. (log(1/b)', for integer b', always simplifies.) If it is set to false', all of these simplifications will be turned off.  Option variable: lognegint   Default value: false' If true' implements the rule log(-n)' -> log(n)+%i*%pi' for n' a positive integer.  Option variable: logsimp   Default value: true' If false' then no simplification of %e' to a power containing log''s is done.  Function: plog (<x>)   Represents the principal branch of the complex-valued natural logarithm with -%pi' < carg(<x>)' <= +%pi' .  Function: sqrt (<x>)   The square root of <x>. It is represented internally by <x>^(1/2)'. See also rootscontract'. radexpand' if true' will cause nth roots of factors of a product which are powers of n to be pulled outside of the radical, e.g. sqrt(16*x^2)' will become 4*x' only if radexpand' is true'.  ## 10.5 Trigonometric Functions  * Introduction to Trigonometric:: * Functions and Variables for Trigonometric::  Option variable: %piargs   Default value: true' When %piargs' is true', trigonometric functions are simplified to algebraic constants when the argument is an integer multiple of %pi, %pi/2, %pi/3, %pi/4, or %pi/6. Maxima knows some identities which can be applied when %pi, etc., are multiplied by an integer variable (that is, a symbol declared to be integer). Examples: (%i1) %piargs : false$
(%i2) [sin (%pi), sin (%pi/2), sin (%pi/3)];
%pi       %pi
(%o2)            [sin(%pi), sin(---), sin(---)]
2         3
(%i3) [sin (%pi/4), sin (%pi/5), sin (%pi/6)];
%pi       %pi       %pi
(%o3)            [sin(---), sin(---), sin(---)]
4         5         6
(%i4) %piargs : true$(%i5) [sin (%pi), sin (%pi/2), sin (%pi/3)]; sqrt(3) (%o5) [0, 1, -------] 2 (%i6) [sin (%pi/4), sin (%pi/5), sin (%pi/6)]; 1 %pi 1 (%o6) [-------, sin(---), -] sqrt(2) 5 2 (%i7) [cos (%pi/3), cos (10*%pi/3), tan (10*%pi/3), cos (sqrt(2)*%pi/3)]; 1 1 sqrt(2) %pi (%o7) [-, - -, sqrt(3), cos(-----------)] 2 2 3 Some identities are applied when %pi and %pi/2 are multiplied by an integer variable. (%i1) declare (n, integer, m, even)$
(%i2) [sin (%pi * n), cos (%pi * m), sin (%pi/2 * m),
cos (%pi/2 * m)];
m/2
(%o2)                  [0, 1, 0, (- 1)   ]


Option variable: %iargs

     Default value: true'

When %iargs' is true', trigonometric functions are simplified to
hyperbolic functions when the argument is apparently a multiple of
the imaginary unit %i.

Even when the argument is demonstrably real, the simplification is
applied; Maxima considers only whether the argument is a literal
multiple of %i.

Examples:

(%i1) %iargs : false$(%i2) [sin (%i * x), cos (%i * x), tan (%i * x)]; (%o2) [sin(%i x), cos(%i x), tan(%i x)] (%i3) %iargs : true$
(%i4) [sin (%i * x), cos (%i * x), tan (%i * x)];
(%o4)           [%i sinh(x), cosh(x), %i tanh(x)]

Even when the argument is demonstrably real, the simplification is
applied.

(%i1) declare (x, imaginary)$(%i2) [featurep (x, imaginary), featurep (x, real)]; (%o2) [true, false] (%i3) sin (%i * x); (%o3) %i sinh(x)  Function: acos (<x>)   - Arc Cosine.  Function: acosh (<x>)   - Hyperbolic Arc Cosine.  Function: acot (<x>)   - Arc Cotangent.  Function: acoth (<x>)   - Hyperbolic Arc Cotangent.  Function: acsc (<x>)   - Arc Cosecant.  Function: acsch (<x>)   - Hyperbolic Arc Cosecant.  Function: asec (<x>)   - Arc Secant.  Function: asech (<x>)   - Hyperbolic Arc Secant.  Function: asin (<x>)   - Arc Sine.  Function: asinh (<x>)   - Hyperbolic Arc Sine.  Function: atan (<x>)   - Arc Tangent.  Function: atan2 (<y>, <x>)   - yields the value of atan(<y>/<x>)' in the interval -%pi' to %pi'.  Function: atanh (<x>)   - Hyperbolic Arc Tangent.  Package: atrig1   The atrig1' package contains several additional simplification rules for inverse trigonometric functions. Together with rules already known to Maxima, the following angles are fully implemented: 0', %pi/6', %pi/4', %pi/3', and %pi/2'. Corresponding angles in the other three quadrants are also available. Do load(atrig1);' to use them.  Function: cos (<x>)   - Cosine.  Function: cosh (<x>)   - Hyperbolic Cosine.  Function: cot (<x>)   - Cotangent.  Function: coth (<x>)   - Hyperbolic Cotangent.  Function: csc (<x>)   - Cosecant.  Function: csch (<x>)   - Hyperbolic Cosecant.  Option variable: halfangles   Default value: false' When halfangles' is true', trigonometric functions of arguments <expr>/2' are simplified to functions of <expr>. For a real argument <x> in the interval 0 < x < 2*%pi' the sine of the half-angle simplifies to a simple formula: sqrt(1 - cos(x)) ---------------- sqrt(2) A complicated factor is needed to make this formula correct for all complex arguments <z>: realpart(z) floor(-----------) 2 %pi (- 1) (1 - unit_step(- imagpart(z)) realpart(z) realpart(z) floor(-----------) - ceiling(-----------) 2 %pi 2 %pi ((- 1) + 1)) Maxima knows this factor and similar factors for the functions sin', cos', sinh', and cosh'. For special values of the argument z these factors simplify accordingly. Examples: (%i1) halfangles:false; (%o1) false (%i2) sin(x/2); x (%o2) sin(-) 2 (%i3) halfangles:true; (%o3) true (%i4) sin(x/2); x floor(-----) 2 %pi sqrt(1 - cos(x)) (- 1) (%o4) ---------------------------------- sqrt(2) (%i5) assume(x>0, x<2*%pi)$
(%i6) sin(x/2);
sqrt(1 - cos(x))
(%o6)                          ----------------
sqrt(2)


Package: ntrig

     The ntrig' package contains a set of simplification rules that are
used to simplify trigonometric function whose arguments are of the
form <f>(<n> %pi/10)' where <f> is any of the functions sin',
cos', tan', csc', sec' and cot'.


Function: sec (<x>)

     - Secant.


Function: sech (<x>)

     - Hyperbolic Secant.


Function: sin (<x>)

     - Sine.


Function: sinh (<x>)

     - Hyperbolic Sine.


Function: tan (<x>)

     - Tangent.


Function: tanh (<x>)

     - Hyperbolic Tangent.


Function: trigexpand (<expr>)

     Expands trigonometric and hyperbolic functions of sums of angles
and of multiple angles occurring in <expr>.  For best results,
<expr> should be expanded.  To enhance user control of
simplification, this function expands only one level at a time,
expanding sums of angles or multiple angles.  To obtain full
expansion into sines and cosines immediately, set the switch
trigexpand: true'.

trigexpand' is governed by the following global flags:

trigexpand'
If true' causes expansion of all expressions containing
sin's and cos's occurring subsequently.

halfangles'
If true' causes half-angles to be simplified away.

trigexpandplus'
Controls the "sum" rule for trigexpand', expansion of sums
(e.g. sin(x + y)') will take place only if trigexpandplus'
is true'.

trigexpandtimes'
Controls the "product" rule for trigexpand', expansion of
products (e.g. sin(2 x)') will take place only if
trigexpandtimes' is true'.

Examples:

(%i1) x+sin(3*x)/sin(x),trigexpand=true,expand;
2           2
(%o1)               - sin (x) + 3 cos (x) + x
(%i2) trigexpand(sin(10*x+y));
(%o2)          cos(10 x) sin(y) + sin(10 x) cos(y)


Option variable: trigexpandplus

     Default value: true'

trigexpandplus' controls the "sum" rule for trigexpand'.  Thus,
when the trigexpand' command is used or the trigexpand' switch
set to true', expansion of sums (e.g. sin(x+y))' will take place
only if trigexpandplus' is true'.


Option variable: trigexpandtimes

     Default value: true'

trigexpandtimes' controls the "product" rule for trigexpand'.
Thus, when the trigexpand' command is used or the trigexpand'
switch set to true', expansion of products (e.g. sin(2*x)') will
take place only if trigexpandtimes' is true'.


Option variable: triginverses

     Default value: true'

triginverses' controls the simplification of the composition of
trigonometric and hyperbolic functions with their inverse
functions.

If all', both e.g. atan(tan(<x>))' and tan(atan(<x>))' simplify
to <x>.

If true', the <arcfun>(<fun>(<x>))' simplification is turned off.

If false', both the <arcfun>(<fun>(<x>))' and
<fun>(<arcfun>(<x>))' simplifications are turned off.


Function: trigreduce

          trigreduce (<expr>, <x>)
trigreduce (<expr>)
Combines products and powers of trigonometric and hyperbolic sin's
and cos's of <x> into those of multiples of <x>.  It also tries to
eliminate these functions when they occur in denominators.  If <x>
is omitted then all variables in <expr> are used.

(%i1) trigreduce(-sin(x)^2+3*cos(x)^2+x);
cos(2 x)      cos(2 x)   1        1
(%o1)          -------- + 3 (-------- + -) + x - -
2             2       2        2


Option variable: trigsign

     Default value: true'

When trigsign' is true', it permits simplification of negative
arguments to trigonometric functions.  E.g., sin(-x)' will become
-sin(x)' only if trigsign' is true'.


Function: trigsimp (<expr>)

     Employs the identities sin(x)^2 + cos(x)^2 = 1 and cosh(x)^2 -
sinh(x)^2 = 1 to simplify expressions containing tan', sec',
etc., to sin', cos', sinh', cosh'.

trigreduce', ratsimp', and radcan' may be able to further
simplify the result.

demo ("trgsmp.dem")' displays some examples of trigsimp'.


Function: trigrat (<expr>)

     Gives a canonical simplified quasilinear form of a trigonometrical
expression; <expr> is a rational fraction of several sin', cos'
or tan', the arguments of them are linear forms in some variables
(or kernels) and %pi/<n>' (<n> integer) with integer coefficients.
The result is a simplified fraction with numerator and denominator
linear in sin' and cos'.  Thus trigrat' linearize always when
it is possible.

(%i1) trigrat(sin(3*a)/sin(a+%pi/3));
(%o1)            sqrt(3) sin(2 a) + cos(2 a) - 1

The following example is taken from Davenport, Siret, and
Tournier, Calcul Formel, Masson (or in English, Addison-Wesley),
section 1.5.5, Morley theorem.

(%i1) c : %pi/3 - a - b$(%i2) bc : sin(a)*sin(3*c)/sin(a+b); %pi sin(a) sin(3 (- b - a + ---)) 3 (%o2) ----------------------------- sin(b + a) (%i3) ba : bc, c=a, a=c; %pi sin(3 a) sin(b + a - ---) 3 (%o3) ------------------------- %pi sin(a - ---) 3 (%i4) ac2 : ba^2 + bc^2 - 2*bc*ba*cos(b); 2 2 %pi sin (3 a) sin (b + a - ---) 3 (%o4) --------------------------- 2 %pi sin (a - ---) 3 %pi - (2 sin(a) sin(3 a) sin(3 (- b - a + ---)) cos(b) 3 %pi %pi sin(b + a - ---))/(sin(a - ---) sin(b + a)) 3 3 2 2 %pi sin (a) sin (3 (- b - a + ---)) 3 + ------------------------------- 2 sin (b + a) (%i5) trigrat (ac2); (%o5) - (sqrt(3) sin(4 b + 4 a) - cos(4 b + 4 a) - 2 sqrt(3) sin(4 b + 2 a) + 2 cos(4 b + 2 a) - 2 sqrt(3) sin(2 b + 4 a) + 2 cos(2 b + 4 a) + 4 sqrt(3) sin(2 b + 2 a) - 8 cos(2 b + 2 a) - 4 cos(2 b - 2 a) + sqrt(3) sin(4 b) - cos(4 b) - 2 sqrt(3) sin(2 b) + 10 cos(2 b) + sqrt(3) sin(4 a) - cos(4 a) - 2 sqrt(3) sin(2 a) + 10 cos(2 a) - 9)/4  ## 10.6 Random Numbers Function: make_random_state   make_random_state (<n>) make_random_state (<s>) make_random_state (true) make_random_state (false) A random state object represents the state of the random number generator. The state comprises 627 32-bit words. make_random_state (<n>)' returns a new random state object created from an integer seed value equal to <n> modulo 2^32. <n> may be negative. make_random_state (<s>)' returns a copy of the random state <s>. make_random_state (true)' returns a new random state object, using the current computer clock time as the seed. make_random_state (false)' returns a copy of the current state of the random number generator.  Function: set_random_state (<s>)   Copies <s> to the random number generator state. set_random_state' always returns done'.  Function: random (<x>)   Returns a pseudorandom number. If <x> is an integer, random (<x>)' returns an integer from 0 through <x> - 1' inclusive. If <x> is a floating point number, random (<x>)' returns a nonnegative floating point number less than <x>. random' complains with an error if <x> is neither an integer nor a float, or if <x> is not positive. The functions make_random_state' and set_random_state' maintain the state of the random number generator. The Maxima random number generator is an implementation of the Mersenne twister MT 19937. Examples: (%i1) s1: make_random_state (654321)$
(%i2) set_random_state (s1);
(%o2)                         done
(%i3) random (1000);
(%o3)                          768
(%i4) random (9573684);
(%o4)                        7657880
(%i5) random (2^75);
(%o5)                11804491615036831636390
(%i6) s2: make_random_state (false)$(%i7) random (1.0); (%o7) .2310127244107132 (%i8) random (10.0); (%o8) 4.394553645870825 (%i9) random (100.0); (%o9) 32.28666704056853 (%i10) set_random_state (s2); (%o10) done (%i11) random (1.0); (%o11) .2310127244107132 (%i12) random (10.0); (%o12) 4.394553645870825 (%i13) random (100.0); (%o13) 32.28666704056853  ## 11 Maximas Database  Introduction to Maximas Database Functions and Variables for Properties Functions and Variables for Facts Functions and Variables for Predicates  ## 11.1 Introduction to Maximas Database ## 11.2 Functions and Variables for Properties Property: alphabetic   alphabetic' is a property type recognized by declare'. The expression declare(<s>, alphabetic)' tells Maxima to recognize as alphabetic all of the characters in <s>, which must be a string. See also *note Identifiers::. Example: (%i1) xx\~yy\\@ : 1729; (%o1) 1729 (%i2) declare ("~@", alphabetic); (%o2) done (%i3) xx~yy@ + @yyxx + xx@@yy~; (%o3) xx@@yy~ + @yyxx + 1729 (%i4) listofvars (%); (%o4) [@yyxx, xx@@yy~]  Property: bindtest   The command declare(<x>, bindtest)' tells Maxima to trigger an error when the symbol <x> is evaluated unbound. (%i1) aa + bb; (%o1) bb + aa (%i2) declare (aa, bindtest); (%o2) done (%i3) aa + bb; aa unbound variable -- an error. Quitting. To debug this try debugmode(true); (%i4) aa : 1234; (%o4) 1234 (%i5) aa + bb; (%o5) bb + 1234  Property: constant   declare(<a>, constant)' declares <a> to be a constant. The declaration of a symbol to be constant does not prevent the assignment of a nonconstant value to the symbol. See constantp' and declare'. Example: (%i1) declare(c, constant); (%o1) done (%i2) constantp(c); (%o2) true (%i3) c : x; (%o3) x (%i4) constantp(c); (%o4) false  Function: constantp (<expr>)   Returns true' if <expr> is a constant expression, otherwise returns false'. An expression is considered a constant expression if its arguments are numbers (including rational numbers, as displayed with /R/'), symbolic constants such as %pi', %e', and %i', variables bound to a constant or declared constant by declare', or functions whose arguments are constant. constantp' evaluates its arguments. See the property constant' which declares a symbol to be constant. Examples: (%i1) constantp (7 * sin(2)); (%o1) true (%i2) constantp (rat (17/29)); (%o2) true (%i3) constantp (%pi * sin(%e)); (%o3) true (%i4) constantp (exp (x)); (%o4) false (%i5) declare (x, constant); (%o5) done (%i6) constantp (exp (x)); (%o6) true (%i7) constantp (foo (x) + bar (%e) + baz (2)); (%o7) false (%i8)  Function: declare (<a_1>, <p_1>, <a_2>, <p_2>, ...)   Assigns the atom or list of atoms <a_i> the property or list of properties <p_i>. When <a_i> and/or <p_i> are lists, each of the atoms gets all of the properties. declare' quotes its arguments. declare' always returns done'. As noted in the description for each declaration flag, for some flags featurep(<object>, <feature>)' returns true' if <object> has been declared to have <feature>. For more information about the features system, see features'. To remove a property from an atom, use remove'. declare' recognizes the following properties: additive' Tells Maxima to simplify <a_i> expressions by the substitution <a_i>(x + y + z + ...)' -->' <a_i>(x) + <a_i>(y) + <a_i>(z) + ...'. The substitution is carried out on the first argument only. alphabetic' Tells Maxima to recognize all characters in <a_i> (which must be a string) as alphabetic characters. antisymmetric, commutative, symmetric' Tells Maxima to recognize <a_i> as a symmetric or antisymmetric function. commutative' is the same as symmetric'. bindtest' Tells Maxima to trigger an error when <a_i> is evaluated unbound. constant' Tells Maxima to consider <a_i> a symbolic constant. even, odd' Tells Maxima to recognize <a_i> as an even or odd integer variable. evenfun, oddfun' Tells Maxima to recognize <a_i> as an odd or even function. evflag' Makes <a_i> known to the ev' function so that <a_i> is bound to true' during the execution of ev' when <a_i> appears as a flag argument of ev'. See evflag'. evfun' Makes <a_i> known to ev' so that the function named by <a_i> is applied when <a_i> appears as a flag argument of ev'. See evfun'. feature' Tells Maxima to recognize <a_i> as the name of a feature. Other atoms may then be declared to have the <a_i> property. increasing, decreasing' Tells Maxima to recognize <a_i> as an increasing or decreasing function. integer, noninteger' Tells Maxima to recognize <a_i> as an integer or noninteger variable. integervalued' Tells Maxima to recognize <a_i> as an integer-valued function. lassociative, rassociative' Tells Maxima to recognize <a_i> as a right-associative or left-associative function. linear' Equivalent to declaring <a_i> both outative' and additive'. mainvar' Tells Maxima to consider <a_i> a "main variable". A main variable succeeds all other constants and variables in the canonical ordering of Maxima expressions, as determined by ordergreatp'. multiplicative' Tells Maxima to simplify <a_i> expressions by the substitution <a_i>(x * y * z * ...)' -->' <a_i>(x) * <a_i>(y) * <a_i>(z) * ...'. The substitution is carried out on the first argument only. nary' Tells Maxima to recognize <a_i> as an n-ary function. The nary' declaration is not the same as calling the nary' function. The sole effect of declare(foo, nary)' is to instruct the Maxima simplifier to flatten nested expressions, for example, to simplify foo(x, foo(y, z))' to foo(x, y, z)'. nonarray' Tells Maxima to consider <a_i> not an array. This declaration prevents multiple evaluation of a subscripted variable name. nonscalar' Tells Maxima to consider <a_i> a nonscalar variable. The usual application is to declare a variable as a symbolic vector or matrix. noun' Tells Maxima to parse <a_i> as a noun. The effect of this is to replace instances of <a_i> with '<a_i>' or nounify(<a_i>)', depending on the context. outative' Tells Maxima to simplify <a_i> expressions by pulling constant factors out of the first argument. When <a_i> has one argument, a factor is considered constant if it is a literal or declared constant. When <a_i> has two or more arguments, a factor is considered constant if the second argument is a symbol and the factor is free of the second argument. posfun' Tells Maxima to recognize <a_i> as a positive function. rational, irrational' Tells Maxima to recognize <a_i> as a rational or irrational real variable. real, imaginary, complex' Tells Maxima to recognize <a_i> as a real, pure imaginary, or complex variable. scalar' Tells Maxima to consider <a_i> a scalar variable.  Property: decreasing  Property: increasing   The commands declare(<f>, decreasing)' or declare(<f>, increasing)' tell Maxima to recognize the function <f> as an decreasing or increasing function. See also declare' for more properties. Example: (%i1) assume(a > b); (%o1) [a > b] (%i2) is(f(a) > f(b)); (%o2) unknown (%i3) declare(f, increasing); (%o3) done (%i4) is(f(a) > f(b)); (%o4) true  Property: even  Property: odd   declare(<a>, even)' or declare(<a>, odd)' tells Maxima to recognize the symbol <a> as an even or odd integer variable. The properties even' and odd' are not recognized by the functions evenp', oddp', and integerp'. See also declare' and askinteger'. Example: (%i1) declare(n, even); (%o1) done (%i2) askinteger(n, even); (%o2) yes (%i3) askinteger(n); (%o3) yes (%i4) evenp(n); (%o4) false  Property: feature   Maxima understands two distinct types of features, system features and features which apply to mathematical expressions. See also status' for information about system features. See also features' and featurep' for information about mathematical features. feature' itself is not the name of a function or variable.  Function: featurep (<a>, <f>)   Attempts to determine whether the object <a> has the feature <f> on the basis of the facts in the current database. If so, it returns true', else false'. Note that featurep' returns false' when neither <f> nor the negation of <f> can be established. featurep' evaluates its argument. See also declare' and features'. (%i1) declare (j, even)$
(%i2) featurep (j, integer);
(%o2)                           true


Declaration: features

     Maxima recognizes certain mathematical properties of functions and
variables.  These are called "features".

declare (<x>, <foo>)' gives the property <foo> to the function or
variable <x>.

declare (<foo>, feature)' declares a new feature <foo>.  For
example, declare ([red, green, blue], feature)' declares three
new features, red', green', and blue'.

The predicate featurep (<x>, <foo>)' returns true' if <x> has
the <foo> property, and false' otherwise.

The infolist features' is a list of known features.  These are

integer        noninteger      even
odd            rational        irrational
real           imaginary       complex
analytic       increasing      decreasing
oddfun         evenfun         posfun
constant       commutative     lassociative
rassociative   symmetric       antisymmetric
integervalued

plus any user-defined features.

features' is a list of mathematical features.  There is also a
list of non-mathematical, system-dependent features.  See status'.

Example:

(%i1) declare (FOO, feature);
(%o1)                         done
(%i2) declare (x, FOO);
(%o2)                         done
(%i3) featurep (x, FOO);
(%o3)                         true


Function: get (<a>, <i>)

     Retrieves the user property indicated by <i> associated with atom
<a> or returns false' if <a> doesn't have property <i>.

get' evaluates its arguments.

See also put' and qput'.

(%i1) put (%e, 'transcendental, 'type);
(%o1)                    transcendental
(%i2) put (%pi, 'transcendental, 'type)$(%i3) put (%i, 'algebraic, 'type)$
(%i4) typeof (expr) := block ([q],
if numberp (expr)
then return ('algebraic),
if not atom (expr)
then return (maplist ('typeof, expr)),
q: get (expr, 'type),
if q=false
then errcatch (error(expr,"is not numeric.")) else q)$(%i5) typeof (2*%e + x*%pi); x is not numeric. (%o5) [[transcendental, []], [algebraic, transcendental]] (%i6) typeof (2*%e + %pi); (%o6) [transcendental, [algebraic, transcendental]]  Property: integer  Property: noninteger   declare(<a>, integer)' or declare(<a>, noninteger)' tells Maxima to recognize <a> as an integer or noninteger variable. See also declare'. Example: (%i1) declare(n, integer, x, noninteger); (%o1) done (%i2) askinteger(n); (%o2) yes (%i3) askinteger(x); (%o3) no  Property: integervalued   declare(<f>, integervalued)' tells Maxima to recognize <f> as an integer-valued function. See also declare'. Example: (%i1) exp(%i)^f(x); %i f(x) (%o1) (%e ) (%i2) declare(f, integervalued); (%o2) done (%i3) exp(%i)^f(x); %i f(x) (%o3) %e  Property: nonarray   The command declare(a, nonarray)' tells Maxima to consider <a> not an array. This declaration prevents multiple evaluation, if <a> is a subscripted variable. See also declare'. Example: (%i1) a:'b$ b:'c$c:'d$

(%i4) a[x];
(%o4)                          d
x
(%i5) declare(a, nonarray);
(%o5)                         done
(%i6) a[x];
(%o6)                          a
x


Property: nonscalar

     Makes atoms behave as does a list or matrix with respect to the
dot operator.

See also declare'.


Function: nonscalarp (<expr>)

     Returns true' if <expr> is a non-scalar, i.e., it contains atoms
declared as non-scalars, lists, or matrices.

See also the predicate function scalarp' and declare'.


Property: posfun

     declare (f, posfun)' declares f' to be a positive function.  is
(f(x) > 0)' yields true'.

See also declare'.


Function: printprops

          printprops (<a>, <i>)
printprops ([<a_1>, ..., <a_n>], <i>)
printprops (all, <i>)
Displays the property with the indicator <i> associated with the
atom <a>.  <a> may also be a list of atoms or the atom all' in
which case all of the atoms with the given property will be used.
For example, printprops ([f, g], atvalue)'.  printprops' is for
properties that cannot otherwise be displayed, i.e.  for atvalue',
atomgrad', gradef', and matchdeclare'.


Function: properties (<a>)

     Returns a list of the names of all the properties associated with
the atom <a>.


System variable: props

     Default value: []'

props' are atoms which have any property other than those
explicitly mentioned in infolists', such as specified by
atvalue', matchdeclare', etc., as well as properties specified
in the declare' function.


Function: propvars (<prop>)

     Returns a list of those atoms on the props' list which have the
property indicated by <prop>.  Thus propvars (atvalue)' returns a
list of atoms which have atvalues.


Function: put (<atom>, <value>, <indicator>)

     Assigns <value> to the property (specified by <indicator>) of
<atom>.  <indicator> may be the name of any property, not just a
system-defined property.

rem' reverses the effect of put'.

put' evaluates its arguments.  put' returns <value>.

See also qput' and get'.

Examples:

(%i1) put (foo, (a+b)^5, expr);
5
(%o1)                       (b + a)
(%i2) put (foo, "Hello", str);
(%o2)                         Hello
(%i3) properties (foo);
(%o3)            [[user properties, str, expr]]
(%i4) get (foo, expr);
5
(%o4)                       (b + a)
(%i5) get (foo, str);
(%o5)                         Hello


Function: qput (<atom>, <value>, <indicator>)

     Assigns <value> to the property (specified by <indicator>) of
<atom>.  This is the same as put', except that the arguments are
quoted.

Example:

(%i1) foo: aa$(%i2) bar: bb$
(%i3) baz: cc$(%i4) put (foo, bar, baz); (%o4) bb (%i5) properties (aa); (%o5) [[user properties, cc]] (%i6) get (aa, cc); (%o6) bb (%i7) qput (foo, bar, baz); (%o7) bar (%i8) properties (foo); (%o8) [value, [user properties, baz]] (%i9) get ('foo, 'baz); (%o9) bar  Property: rational  Property: irrational   declare(<a>, rational)' or declare(<a>, irrational)' tells Maxima to recognize <a> as a rational or irrational real variable. See also declare'.  Property: real  Property: imaginary  Property: complex   declare(<a>, real)', declare(<a>, imaginary)', or declare(<a>, complex)' tells Maxima to recognize <a> as a real, pure imaginary, or complex variable. See also declare'.  Function: rem (<atom>, <indicator>)   Removes the property indicated by <indicator> from <atom>. rem' reverses the effect of put'. rem' returns done' if <atom> had an <indicator> property when rem' was called, or false' if it had no such property.  Function: remove   remove (<a_1>, <p_1>, ..., <a_n>, <p_n>) remove ([<a_1>, ..., <a_m>], [<p_1>, ..., <p_n>], ...) remove ("<a>", operator) remove (<a>, transfun) remove (all, <p>) Removes properties associated with atoms. remove (<a_1>, <p_1>, ..., <a_n>, <p_n>)' removes property p_k' from atom a_k'. remove ([<a_1>, ..., <a_m>], [<p_1>, ..., <p_n>], ...)' removes properties <p_1>, ..., <p_n>' from atoms <a_1>, ..., <a_m>. There may be more than one pair of lists. remove (all, <p>)' removes the property <p> from all atoms which have it. The removed properties may be system-defined properties such as function', macro', or mode_declare'. remove' does not remove properties defined by put'. A property may be transfun' to remove the translated Lisp version of a function. After executing this, the Maxima version of the function is executed rather than the translated version. remove ("<a>", operator)' or, equivalently, remove ("<a>", op)' removes from <a> the operator properties declared by prefix', infix', nary', postfix', matchfix', or nofix'. Note that the name of the operator must be written as a quoted string. remove' always returns done' whether or not an atom has a specified property. This behavior is unlike the more specific remove functions remvalue', remarray', remfunction', and remrule'. remove' quotes its arguments.  Property: scalar   declare(<a>, scalar)' tells Maxima to consider <a> a scalar variable. See also declare'.  Function: scalarp (<expr>)   Returns true' if <expr> is a number, constant, or variable declared scalar' with declare', or composed entirely of numbers, constants, and such variables, but not containing matrices or lists. See also the predicate function nonscalarp'.  ## 11.3 Functions and Variables for Facts Function: activate (<context_1>, ..., <context_n>)   Activates the contexts <context_1>, ..., <context_n>. The facts in these contexts are then available to make deductions and retrieve information. The facts in these contexts are not listed by facts ()'. The variable activecontexts' is the list of contexts which are active by way of the activate' function.  System variable: activecontexts   Default value: []' activecontexts' is a list of the contexts which are active by way of the activate' function, as opposed to being active because they are subcontexts of the current context.  Function: askinteger   askinteger (<expr>, integer) askinteger (<expr>) askinteger (<expr>, even) askinteger (<expr>, odd) askinteger (<expr>, integer)' attempts to determine from the assume' database whether <expr> is an integer. askinteger' prompts the user if it cannot tell otherwise, and attempt to install the information in the database if possible. askinteger (<expr>)' is equivalent to askinteger (<expr>, integer)'. askinteger (<expr>, even)' and askinteger (<expr>, odd)' likewise attempt to determine if <expr> is an even integer or odd integer, respectively.  Function: asksign (<expr>)   First attempts to determine whether the specified expression is positive, negative, or zero. If it cannot, it asks the user the necessary questions to complete its deduction. The user's answer is recorded in the data base for the duration of the current computation. The return value of asksign' is one of pos', neg', or zero'.  Function: assume (<pred_1>, ..., <pred_n>)   Adds predicates <pred_1>, ..., <pred_n> to the current context. If a predicate is inconsistent or redundant with the predicates in the current context, it is not added to the context. The context accumulates predicates from each call to assume'. assume' returns a list whose elements are the predicates added to the context or the atoms redundant' or inconsistent' where applicable. The predicates <pred_1>, ..., <pred_n> can only be expressions with the relational operators < <= equal notequal >=' and >'. Predicates cannot be literal equality =' or literal inequality #' expressions, nor can they be predicate functions such as integerp'. Compound predicates of the form <pred_1> and ... and <pred_n>' are recognized, but not <pred_1> or ... or <pred_n>'. not <pred_k>' is recognized if <pred_k> is a relational predicate. Expressions of the form not (<pred_1> and <pred_2>)' and not (<pred_1> or <pred_2>)' are not recognized. Maxima's deduction mechanism is not very strong; there are many obvious consequences which cannot be determined by is'. This is a known weakness. assume' does not handle predicates with complex numbers. If a predicate contains a complex number assume' returns inconsistent' or redunant'. assume' evaluates its arguments. See also is', facts', forget', context', and declare'. Examples: (%i1) assume (xx > 0, yy < -1, zz >= 0); (%o1) [xx > 0, yy < - 1, zz >= 0] (%i2) assume (aa < bb and bb < cc); (%o2) [bb > aa, cc > bb] (%i3) facts (); (%o3) [xx > 0, - 1 > yy, zz >= 0, bb > aa, cc > bb] (%i4) is (xx > yy); (%o4) true (%i5) is (yy < -yy); (%o5) true (%i6) is (sinh (bb - aa) > 0); (%o6) true (%i7) forget (bb > aa); (%o7) [bb > aa] (%i8) prederror : false; (%o8) false (%i9) is (sinh (bb - aa) > 0); (%o9) unknown (%i10) is (bb^2 < cc^2); (%o10) unknown  Option variable: assumescalar   Default value: true' assumescalar' helps govern whether expressions expr' for which nonscalarp (expr)' is false' are assumed to behave like scalars for certain transformations. Let expr' represent any expression other than a list or a matrix, and let [1, 2, 3]' represent any list or matrix. Then expr . [1, 2, 3]' yields [expr, 2 expr, 3 expr]' if assumescalar' is true', or scalarp (expr)' is true', or constantp (expr)' is true'. If assumescalar' is true', such expressions will behave like scalars only for commutative operators, but not for noncommutative multiplication .'. When assumescalar' is false', such expressions will behave like non-scalars. When assumescalar' is all', such expressions will behave like scalars for all the operators listed above.  Option variable: assume_pos   Default value: false' When assume_pos' is true' and the sign of a parameter <x> cannot be determined from the current context or other considerations, sign' and asksign (<x>)' return true'. This may forestall some automatically-generated asksign' queries, such as may arise from integrate' or other computations. By default, a parameter is <x> such that symbolp (<x>)' or subvarp (<x>)'. The class of expressions considered parameters can be modified to some extent via the variable assume_pos_pred'. sign' and asksign' attempt to deduce the sign of expressions from the sign of operands within the expression. For example, if a' and b' are both positive, then a + b' is also positive. However, there is no way to bypass all asksign' queries. In particular, when the asksign' argument is a difference <x> - <y>' or a logarithm log(<x>)', asksign' always requests an input from the user, even when assume_pos' is true' and assume_pos_pred' is a function which returns true' for all arguments.  Option variable: assume_pos_pred   Default value: false' When assume_pos_pred' is assigned the name of a function or a lambda expression of one argument <x>, that function is called to determine whether <x> is considered a parameter for the purpose of assume_pos'. assume_pos_pred' is ignored when assume_pos' is false'. The assume_pos_pred' function is called by sign' and asksign' with an argument <x> which is either an atom, a subscripted variable, or a function call expression. If the assume_pos_pred' function returns true', <x> is considered a parameter for the purpose of assume_pos'. By default, a parameter is <x> such that symbolp (<x>)' or subvarp (<x>)'. See also assume' and assume_pos'. Examples: (%i1) assume_pos: true$
(%i2) assume_pos_pred: symbolp$(%i3) sign (a); (%o3) pos (%i4) sign (a); (%o4) pnz (%i5) assume_pos_pred: lambda ([x], display (x), true)$
x = a

(%o6)                          pos
x = a
1

(%o7)                          pos
x = foo(a)

(%o8)                          pos
(%i9) asksign (foo (a) + bar (b));
x = foo(a)

x = bar(b)

(%o9)                          pos
x = a

Is  a - 1  positive, negative, or zero?

p;
(%o10)                         pos
x = a

x = b

x = a

x = b

Is  b - a  positive, negative, or zero?

p;
(%o11)                         neg


Option variable: context

     Default value: initial'

context' names the collection of facts maintained by assume' and
forget'.  assume' adds facts to the collection named by
context', while forget' removes facts.

Binding context' to a name <foo> changes the current context to
<foo>.  If the specified context <foo> does not yet exist, it is
created automatically by a call to newcontext'.  The specified
context is activated automatically.

See contexts' for a general description of the context mechanism.


Option variable: contexts

     Default value: [initial, global]'

contexts' is a list of the contexts which currently exist,
including the currently active context.

The context mechanism makes it possible for a user to bind together
and name a collection of facts, called a context.  Once this is
done, the user can have Maxima assume or forget large numbers of
facts merely by activating or deactivating their context.

Any symbolic atom can be a context, and the facts contained in that
context will be retained in storage until destroyed one by one by
calling forget' or destroyed as a whole by calling kill' to
destroy the context to which they belong.

Contexts exist in a hierarchy, with the root always being the
context global', which contains information about Maxima that some
functions need.  When in a given context, all the facts in that
context are "active" (meaning that they are used in deductions and
retrievals) as are all the facts in any context which is a
subcontext of the active context.

When a fresh Maxima is started up, the user is in a context called
initial', which has global' as a subcontext.

See also facts', newcontext', supcontext', killcontext',
activate', deactivate', assume', and forget'.


Function: deactivate (<context_1>, ..., <context_n>)

     Deactivates the specified contexts <context_1>, ..., <context_n>.


Function: facts

          facts (<item>)
facts ()
If <item> is the name of a context, facts (<item>)' returns a
list of the facts in the specified context.

If <item> is not the name of a context, facts (<item>)' returns a
list of the facts known about <item> in the current context.
Facts that are active, but in a different context, are not listed.

facts ()' (i.e., without an argument) lists the current context.


Function: forget

          forget (<pred_1>, ..., <pred_n>)
forget (<L>)
Removes predicates established by assume'.  The predicates may be
expressions equivalent to (but not necessarily identical to) those
previously assumed.

forget (<L>)', where <L> is a list of predicates, forgets each
item on the list.


Function: is (<expr>)

     Attempts to determine whether the predicate <expr> is provable
from the facts in the assume' database.

If the predicate is provably true' or false', is' returns
true' or false', respectively.  Otherwise, the return value is
governed by the global flag prederror'.  When prederror' is
true', is' complains with an error message.  Otherwise, is'
returns unknown'.

ev(<expr>, pred)' (which can be written  <expr>, pred' at the
interactive prompt) is equivalent to is(<expr>)'.

See also assume', facts', and maybe'.

Examples:

is' causes evaluation of predicates.

(%i1) %pi > %e;
(%o1)                       %pi > %e
(%i2) is (%pi > %e);
(%o2)                         true

is' attempts to derive predicates from the assume' database.

(%i1) assume (a > b);
(%o1)                        [a > b]
(%i2) assume (b > c);
(%o2)                        [b > c]
(%i3) is (a < b);
(%o3)                         false
(%i4) is (a > c);
(%o4)                         true
(%i5) is (equal (a, c));
(%o5)                         false

If is' can neither prove nor disprove a predicate from the
assume' database, the global flag prederror' governs the
behavior of is'.

(%i1) assume (a > b);
(%o1)                        [a > b]
(%i2) prederror: true$(%i3) is (a > 0); Maxima was unable to evaluate the predicate: a > 0 -- an error. Quitting. To debug this try debugmode(true); (%i4) prederror: false$
(%i5) is (a > 0);
(%o5)                        unknown


Function: killcontext (<context_1>, ..., <context_n>)

     Kills the contexts <context_1>, ..., <context_n>.

If one of the contexts is the current context, the new current
context will become the first available subcontext of the current
context which has not been killed.  If the first available
unkilled context is global' then initial' is used instead.  If
the initial' context is killed, a new, empty initial' context is
created.

killcontext' refuses to kill a context which is currently active,
either because it is a subcontext of the current context, or by
use of the function activate'.

killcontext' evaluates its arguments.  killcontext' returns
done'.


Function: maybe (<expr>)

     Attempts to determine whether the predicate <expr> is provable
from the facts in the assume' database.

If the predicate is provably true' or false', maybe' returns
true' or false', respectively.  Otherwise, maybe' returns
unknown'.

maybe' is functionally equivalent to is' with prederror:
false', but the result is computed without actually assigning a
value to prederror'.

See also assume', facts', and is'.

Examples:

(%i1) maybe (x > 0);
(%o1)                        unknown
(%i2) assume (x > 1);
(%o2)                        [x > 1]
(%i3) maybe (x > 0);
(%o3)                         true


Function: newcontext

          newcontext (<name>)
newcontext ()
Creates a new, empty context, called <name>, which has global' as
its only subcontext.  The newly-created context becomes the
currently active context.

If <name> is not specified, a new name is created (via gensym')
and returned.

newcontext' evaluates its argument.  newcontext' returns <name>
(if specified) or the new context name.


Function: sign (<expr>)

     Attempts to determine the sign of <expr> on the basis of the facts
in the current data base.  It returns one of the following
answers: pos' (positive), neg' (negative), zero', pz'
(positive or zero), nz' (negative or zero), pn' (positive or
negative), or pnz' (positive, negative, or zero, i.e. nothing
known).


Function: supcontext

          supcontext (<name>, <context>)
supcontext (<name>)
supcontext ()
Creates a new context, called <name>, which has <context> as a
subcontext.  <context> must exist.

If <context> is not specified, the current context is assumed.

If <name> is not specified, a new name is created (via gensym')
and returned.

supcontext' evaluates its argument.  supcontext' returns <name>
(if specified) or the new context name.



## 11.4 Functions and Variables for Predicates

Function: charfun (<p>)

     Return 0 when the predicate <p> evaluates to false'; return 1 when
the predicate evaluates to true'.  When the predicate evaluates to
something other than true' or false' (unknown),  return a noun
form.

Examples:

(%i1) charfun (x < 1);
(%o1)                    charfun(x < 1)
(%i2) subst (x = -1, %);
(%o2)                           1
(%i3) e : charfun ('"and" (-1 < x, x < 1))$(%i4) [subst (x = -1, e), subst (x = 0, e), subst (x = 1, e)]; (%o4) [0, 1, 0]  Function: compare (<x>, <y>)   Return a comparison operator <op> (<', <=', >', >=', =', or #') such that is (<x> <op> <y>)' evaluates to true'; when either <x> or <y> depends on %i' and <x> # <y>', return notcomparable'; when there is no such operator or Maxima isn't able to determine the operator, return unknown'. Examples: (%i1) compare (1, 2); (%o1) < (%i2) compare (1, x); (%o2) unknown (%i3) compare (%i, %i); (%o3) = (%i4) compare (%i, %i + 1); (%o4) notcomparable (%i5) compare (1/x, 0); (%o5) # (%i6) compare (x, abs(x)); (%o6) <= The function compare' doesn't try to determine whether the real domains of its arguments are nonempty; thus (%i1) compare (acos (x^2 + 1), acos (x^2 + 1) + 1); (%o1) < The real domain of acos (x^2 + 1)' is empty.  Function: equal (<a>, <b>)   Represents equivalence, that is, equal value. By itself, equal' does not evaluate or simplify. The function is' attempts to evaluate equal' to a Boolean value. is(equal(<a>, <b>))' returns true' (or false') if and only if <a> and <b> are equal (or not equal) for all possible values of their variables, as determined by evaluating ratsimp(<a> - <b>)'; if ratsimp' returns 0, the two expressions are considered equivalent. Two expressions may be equivalent even if they are not syntactically equal (i.e., identical). When is' fails to reduce equal' to true' or false', the result is governed by the global flag prederror'. When prederror' is true', is' complains with an error message. Otherwise, is' returns unknown'. In addition to is', some other operators evaluate equal' and notequal' to true' or false', namely if', and', or', and not'. The negation of equal' is notequal'. Examples: By itself, equal' does not evaluate or simplify. (%i1) equal (x^2 - 1, (x + 1) * (x - 1)); 2 (%o1) equal(x - 1, (x - 1) (x + 1)) (%i2) equal (x, x + 1); (%o2) equal(x, x + 1) (%i3) equal (x, y); (%o3) equal(x, y) The function is' attempts to evaluate equal' to a Boolean value. is(equal(<a>, <b>))' returns true' when ratsimp(<a> - <b>)' returns 0. Two expressions may be equivalent even if they are not syntactically equal (i.e., identical). (%i1) ratsimp (x^2 - 1 - (x + 1) * (x - 1)); (%o1) 0 (%i2) is (equal (x^2 - 1, (x + 1) * (x - 1))); (%o2) true (%i3) is (x^2 - 1 = (x + 1) * (x - 1)); (%o3) false (%i4) ratsimp (x - (x + 1)); (%o4) - 1 (%i5) is (equal (x, x + 1)); (%o5) false (%i6) is (x = x + 1); (%o6) false (%i7) ratsimp (x - y); (%o7) x - y (%i8) is (equal (x, y)); (%o8) unknown (%i9) is (x = y); (%o9) false When is' fails to reduce equal' to true' or false', the result is governed by the global flag prederror'. (%i1) [aa : x^2 + 2*x + 1, bb : x^2 - 2*x - 1]; 2 2 (%o1) [x + 2 x + 1, x - 2 x - 1] (%i2) ratsimp (aa - bb); (%o2) 4 x + 2 (%i3) prederror : true; (%o3) true (%i4) is (equal (aa, bb)); Maxima was unable to evaluate the predicate: 2 2 equal(x + 2 x + 1, x - 2 x - 1) -- an error. Quitting. To debug this try debugmode(true); (%i5) prederror : false; (%o5) false (%i6) is (equal (aa, bb)); (%o6) unknown Some operators evaluate equal' and notequal' to true' or false'. (%i1) if equal (y, y - 1) then FOO else BAR; (%o1) BAR (%i2) eq_1 : equal (x, x + 1); (%o2) equal(x, x + 1) (%i3) eq_2 : equal (y^2 + 2*y + 1, (y + 1)^2); 2 2 (%o3) equal(y + 2 y + 1, (y + 1) ) (%i4) [eq_1 and eq_2, eq_1 or eq_2, not eq_1]; (%o4) [false, true, true] Because not <expr>' causes evaluation of <expr>, not equal(<a>, <b>)' is equivalent to is(notequal(<a>, <b>))'. (%i1) [notequal (2*z, 2*z - 1), not equal (2*z, 2*z - 1)]; (%o1) [notequal(2 z, 2 z - 1), true] (%i2) is (notequal (2*z, 2*z - 1)); (%o2) true  Function: notequal (<a>, <b>)   Represents the negation of equal(<a>, <b>)'. Examples: (%i1) equal (a, b); (%o1) equal(a, b) (%i2) maybe (equal (a, b)); (%o2) unknown (%i3) notequal (a, b); (%o3) notequal(a, b) (%i4) not equal (a, b); (%o4) notequal(a, b) (%i5) maybe (notequal (a, b)); (%o5) unknown (%i6) assume (a > b); (%o6) [a > b] (%i7) equal (a, b); (%o7) equal(a, b) (%i8) maybe (equal (a, b)); (%o8) false (%i9) notequal (a, b); (%o9) notequal(a, b) (%i10) maybe (notequal (a, b)); (%o10) true  Function: unknown (<expr>)   Returns true' if and only if <expr> contains an operator or function not recognized by the Maxima simplifier.  Function: zeroequiv (<expr>, <v>)   Tests whether the expression <expr> in the variable <v> is equivalent to zero, returning true', false', or dontknow'. zeroequiv' has these restrictions: 1. Do not use functions that Maxima does not know how to differentiate and evaluate. 2. If the expression has poles on the real line, there may be errors in the result (but this is unlikely to occur). 3. If the expression contains functions which are not solutions to first order differential equations (e.g. Bessel functions) there may be incorrect results. 4. The algorithm uses evaluation at randomly chosen points for carefully selected subexpressions. This is always a somewhat hazardous business, although the algorithm tries to minimize the potential for error. For example zeroequiv (sin(2 * x) - 2 * sin(x) * cos(x), x)' returns true' and zeroequiv (%e^x + x, x)' returns false'. On the other hand zeroequiv (log(a * b) - log(a) - log(b), a)' returns dontknow' because of the presence of an extra parameter b'.  ## 12 Plotting  Introduction to Plotting Plotting Formats Functions and Variables for Plotting Plotting Options Gnuplot Options Gnuplot_pipes Format Functions  ## 12.1 Introduction to Plotting Maxima uses an external plotting package to make the plots (see the section on Plotting Formats'). The plotting functions calculate a set of points and pass them to the plotting package together with a set of commands. That information can be passed to the external program either through a pipe or by calling the program with the name of a file where the data has been saved. The data file is given the name maxout.format', where format' is the name of the plotting format being used (gnuplot', xmaxima', mgnuplot' or gnuplot_pipes'). There are to save the plot in a graphic format file. In those cases, the file maxout.format' created by Maxima includes commands that will make the external plotting program save the result in a graphic file. The default name for that graphic file is maxplot.extension', where extension' is the extension normally used for the kind of graphic file selected. The maxout.format' and maxplot.extension' files are created in the directory specified by the system variable maxima_tempdir'. That location can be changed by assigning to that variable (or to the environment variable MAXIMA_TEMPDIR) a string that represents a valid directory where Maxima can create new files. The output of the Maxima plotting command will be a list with the names of the file(s) created, including their complete path. If the format used is either gnuplot' or xmaxima', the external programs gnuplot' or xmaxima' can be run, giving it the file maxout.format' as argument, in order to view again a plot previously created in Maxima. Thus, when a Maxima plotting command fails, the format can be set to gnuplot' or xmaxima' and the plain-text file maxout.gnuplot' (or maxout.xmaxima') can be inspected to look for the source of the problem. The additional package *note draw:: provides functions similar to the ones described in this section with some extra features. Note that some plotting options have the same name in both plotting packages, but their syntax and behavior is different. To view the documentation for a graphic option opt', type ?? opt' in order to choose the information for either of those two packages.  ## 12.2 Plotting Formats Maxima can use either Gnuplot or Xmaxima as graphics program. Gnuplot is an external program that has to be installed separately, while Xmaxima is distributed with Maxima. There are various different formats for those programs, which can be selected with the option plot_format' (see also the Plotting Options' section). The plotting formats are the following: * *gnuplot* (default on Windows) Used to launch the external program gnuplot, which must be installed in your system. All plotting commands and data are saved into the file maxout.gnuplot'. * *gnuplot_pipes* (default on non-Windows platforms) This format is not available in Windows platforms. It is similar to the gnuplot' format except that the commands are sent to gnuplot through a pipe, while the data are saved into the file maxout.gnuplot_pipes'. A single gnuplot process is kept open and subsequent plot commands will be sent to the same process, replacing previous plots, unless the gnuplot pipe is closed with the function gnuplot_close'. When this format is used, the function gnuplot_replot' can be used to modify a plot that has already displayed on the screen. This format is only used to plot to the screen; whenever graphic files are created, the format is silently switched to gnuplot' and the commands needed to create the graphic file are saved with the data in file maxout.gnuplot'. * *mgnuplot* Mgnuplot is a Tk-based wrapper around gnuplot. It is included in the Maxima distribution. Mgnuplot offers a rudimentary GUI for gnuplot, but has fewer overall features than the plain gnuplot interface. Mgnuplot requires an external gnuplot installation and, in Unix systems, the Tcl/Tk system. * *xmaxima* Xmaxima is a Tcl/Tk graphical interface for Maxima that can also be used to display plots created when Maxima is run from the console or from other graphical interfaces. To use this format, the xmaxima program, which is distributed together with Maxima, should be installed. If Maxima is being run from the Xmaxima console, the data and commands are passed to xmaxima through the same socket used for the communication between Maxima and the Xmaxima console. When used from a terminal or from graphical interfaces different from Xmaxima, the commands and data are saved in the file maxout.xmaxima' and xmaxima is run with the name of that file as argument. In previous versions this format used to be called openmath'; that old name still works as a synonym for xmaxima'.  ## 12.3 Functions and Variables for Plotting Function: contour_plot (<expr>, <x_range>, <y_range>, <options>, ...)   It plots the contours (curves of equal value) of <expr> over the region <x_range> by <y_range>. Any additional arguments are treated the same as in plot3d'. This function only works when the plot format is either gnuplot' or gnuplot_pipes'. The additional package implicit_plot', which works in any graphic format, can also be used to plot contours but a separate expression must be given for each contour. Examples: (%i1) contour_plot (x^2 + y^2, [x, -4, 4], [y, -4, 4])$

You can add any options accepted by plot3d'; for instance, the
option legend' with a value of false, to remove the legend. By
default, Gnuplot chooses and displays 3 contours. To increase the
number of contours, it is necessary to use a custom
gnuplot_preamble', as in the next example:

(%i1) contour_plot (u^3 + v^2, [u, -4, 4], [v, -4, 4],
[legend,false],
[gnuplot_preamble, "set cntrparam levels 12"])$ Function: get_plot_option (<keyword>, <index>)   Returns the current default value of the option named <keyword>, which is a list. The optional argument <index> must be a positive integer which can be used to extract only one element from the list (element 1 is the name of the option). See also set_plot_option', remove_plot_option' and the section on Plotting Options.  System variable: gnuplot_command   This variable stores the name of the command used to run the gnuplot program when the plot format is gnuplot'. Its default value is "wgnuplot" in Windows and "gnuplot" in other systems. If the gnuplot program is not found unless you give its complete path or if you want to try a different version of it, you may change the value of this variable. For instance, (%i1) gnuplot_command: "/usr/local/bin/my_gnuplot"$


System variable: gnuplot_file_args

     When a graphic file is going to be created using gnuplot', this
variable is used to specify the way the file name should be passed
to gnuplot. Its default value is "~s", which means that the name
of the file will be passed directly. The contents of this variable
can be changed in order to add options for the gnuplot program,
adding those options before the format directive "~s".


System variable: gnuplot_view_args

     This variable is used to parse the argument that will be passed to
the gnuplot program when the plot format is gnuplot'. Its default
value is "-persist ~s", where "~s" will be replaced with the name
of the file where the gnuplot commands have been written (usually
"maxout.gnuplot"). The option -persist' tells gnuplot to exit
after the commands in the file have been executed, without closing
the window that displays the plot.

Those familiar with gnuplot, might want to change the value of this
variable. For example, by changing it to:

(%i1) gnuplot_view_args: "~s -"$gnuplot will not be closed after the commands in the file have been executed; thus, the window with the plot will remain, as well as the gnuplot interactive shell where other commands can be issued in order to modify the plot. In Windows versions of Gnuplot older than 4.6.3 the behavior of "~s -" and "-persist ~s" were the opposite; namely, "-persist ~s" made the plot window and the gnuplot interactive shell remain, while "~s -" closed the gnuplot shell keeping the plot window. Therefore, when older gnuplot versions are used in Windows, it might be necessary to adjust the value of gnuplot_view_args'.  Function: implicit_plot   implicit_plot (<expr>, <x_range>, <y_range>) implicit_plot ([<expr_1>, ..., <expr_n>], <x_range>, <y_range>) Displays a plot of a function on the real plane, defined implicitly by the expression <expr>. The domain in the plane is defined by <x_range> and <y_range>. Several functions can be represented on the same plot, giving a list [<expr_1>, ..., <expr_n>] of expressions that define them. This function uses the global format options set up with the set_plot_option'. Additional options can also be given as extra arguments for the implicit_plot' command. The method used by implicit_plot' consists of tracking sign changes on the domain given and it can fail for complicated expressions. load(implicit_plot)' loads this function. Example: (%i1) load(implicit_plot)$
(%i2) implicit_plot (x^2 = y^3 - 3*y + 1, [x, -4, 4], [y, -4, 4])$ Function: julia (<x>, <y>, ...<options>...)   Creates a graphic representation of the Julia set for the complex number (<x> + i <y>). The two mandatory parameters <x> and <y> must be real. This program is part of the additional package dynamics', but that package does not have to be loaded; the first time julia is used, it will be loaded automatically. Each pixel in the grid is given a color corresponding to the number of iterations it takes the sequence that starts at that point to move out of the convergence circle of radius 2 centered at the origin. The number of pixels in the grid is controlled by the grid' plot option (default 30 by 30). The maximum number of iterations is set with the option iterations'. The program uses its own default palette: magenta,violet, blue, cyan, green, yellow, orange, red, brown and black, but it can be changed by adding an explicit palette' option in the command. The default domain used goes from -2 to 2 in both axes and can be changed with the x' and y' options. By default, the two axes are shown with the same scale, unless the option yx_ratio' is used or the option same_xy' is disabled. Other general plot options are also accepted. The following example shows a region of the Julia set for the number -0.55 + i0.6. The option color_bar_tics' is used to prevent Gnuplot from adjusting the color box up to 40, in which case the points corresponding the maximum 36 iterations would not be black. (%i1) julia (-0.55, 0.6, [iterations, 36], [x, -0.3, 0.2], [y, 0.3, 0.9], [grid, 400, 400], [color_bar_tics, 0, 6, 36])$


Function: make_transform ([<var1>, <var2>, <var3>], <fx>, <fy>, <fz>)

     Returns a function suitable to be used in the option transform_xy'
of plot3d.  The three variables <var1>, <var2>, <var3> are three
dummy variable names, which represent the 3 variables given by the
plot3d command (first the two independent variables and then the
function that depends on those two variables).  The three functions
<fx>, <fy>, <fz> must depend only on those 3 variables, and will
give the corresponding x, y and z coordinates that should be
plotted.  There are two transformations defined by default:
polar_to_xy' and spherical_to_xyz'. See the documentation for
those two transformations.


Function: mandelbrot (<options>)

     Creates a graphic representation of the Mandelbrot set. This
program is part of the additional package dynamics', but that
package does not have to be loaded; the first time mandelbrot is
used, the package will be loaded automatically.

This program can be called without any arguments, in which case it
will use a default value of 9 iterations per point, a grid with
dimensions set by the grid' plot option (default 30 by 30) and a
region that extends from -2 to 2 in both axes. The options are all
the same that plot2d accepts, plus an option iterations' to
change the number of iterations.

Each pixel in the grid is given a color corresponding to the
number of iterations it takes the sequence starting at zero to
move out of the convergence circle of radius 2, centered at the
origin. The maximum number of iterations is set by the option
iterations'.  The program uses its own default palette:
magenta,violet, blue, cyan, green, yellow, orange, red, brown and
black, but it can be changed by adding an explicit palette'
option in the command. By default, the two axes are shown with the
same scale, unless the option yx_ratio' is used or the option
same_xy' is disabled.

Example:

[grid,400,400])$(%i1) mandelbrot ([iterations, 30], [x, -2, 1], [y, -1.2, 1.2], [grid,400,400])$


System function: polar_to_xy

     It can be given as value for the transform_xy' option of plot3d.
Its effect will be to interpret the two independent variables in
plot3d as the distance from the z axis and the azimuthal angle
(polar coordinates), and transform them into x and y coordinates.


Function: plot2d

          plot2d (<plot>, <x_range>, ..., <options>, ...)
plot2d ([<plot_1>, ..., <plot_n>], ..., <options>, ...)
plot2d ([<plot_1>, ..., <plot_n>], <x_range>, ..., <options>,
...)
Where <plot>, <plot_1>, ..., <plot_n> can be either expressions,
function names or a list with the any of the forms: [discrete,
[<x1>, ..., <xn>], [<y1>, ..., <yn>]]', [discrete, [[<x1>, <y1>],
..., [<xn>, ..., <yn>]]]' or [parametric, <x_expr>, <y_expr>,
<t_range>]'.

Displays a plot of one or more expressions as a function of one
variable or parameter.

plot2d' displays one or several plots in two dimensions.  When
expressions or function name are used to define the plots, they
should all depend on only one variable <var> and the use of
<x_range> will be mandatory, to provide the name of the variable
and its minimum and maximum values; the syntax for <x_range> is:
[<variable>, <min>, <max>]'.

A plot can also be defined in the discrete or parametric forms.
The discrete form is used to plot a set of points with given
coordinates.  A discrete plot is defined by a list starting with
the keyword <discrete>, followed by one or two lists of values.
If two lists are given, they must have the same length; the first
list will be interpreted as the x coordinates of the points to be
plotted and the second list as the y coordinates.  If only one
list is given after the <discrete> keyword, each element on the
list could also be a list with two values that correspond to the x
and y coordinates of a point, or it could be a sequence of
numerical values which will be plotted at consecutive integer
values (1,2,3,...) on the x axis.

A parametric plot is defined by a list starting with the keyword
<parametric>, followed by two expressions or function names and a
range for the parameter.  The range for the parameter must be a
list with the name of the parameter followed by its minimum and
maximum values: [<param>, <min>, <max>]'.  The plot will show the
path traced out by the point with coordinates given by the two
expressions or functions, as <param> increases from <min> to <max>.

A range for the vertical axis is an optional argument with the
form: [y, <min>, <max>]' (the keyword <y> is always used for the
vertical axis).  If that option is used, the plot will show that
exact vertical range, independently of the values reached by the
plot.  If the vertical range is not specified, it will be set up
according to the minimum and maximum values of the second
coordinate of the plot points.

All other options should also be lists, starting with a keyword and
followed by one or more values.  See plot_options'.

If there are several plots to be plotted, a legend will be written
to identity each of the expressions.  The labels that should be
used in that legend can be given with the option legend'.  If that
option is not used, Maxima will create labels from the expressions
or function names.

*Examples:*

Plot of a common function:

(%i1) plot2d (sin(x), [x, -%pi, %pi])$If the function grows too fast, it might be necessary to limit the values in the vertical axis using the y' option: (%i1) plot2d (sec(x), [x, -2, 2], [y, -20, 20])$

When the plot box is disabled, no labels are created for the axes.
In that case, instead of using xlabel' and ylabel' to set the
names of the axes, it is better to use option label', which
allows more flexibility. Option yx_ratio' is used to change the
default rectangular shape of the plot; in this example the plot
will fill a square.

(%i1) plot2d ( x^2 - 1, [x, -3, 3], [box, false], grid2d,
[yx_ratio, 1], [axes, solid], [xtics, -2, 4, 2],
[ytics, 2, 2, 6], [label, ["x", 2.9, -0.3],
["x^2-1", 0.1, 8]], [title, "A parabola"])$A plot with a logarithmic scale in the vertical axis: (%i1) plot2d (exp(3*s), [s, -2, 2], logy)$

Plotting functions by name:

(%i1) F(x) := x^2 $(%i2) :lisp (defun |$g| (x) (m* x x x))
$g (%i2) H(x) := if x < 0 then x^4 - 1 else 1 - x^5$
(%i3) plot2d ([F, G, H], [u, -1, 1], [y, -1.5, 1.5])$A plot of the butterfly curve, defined parametrically: (%i1) r: (exp(cos(t))-2*cos(4*t)-sin(t/12)^5)$
(%i2) plot2d([parametric, r*sin(t), r*cos(t), [t, -8*%pi, 8*%pi]])$Plot of a circle, using its parametric representation, together with the function -|x|. The circle will only look like a circle if the scale in the two axes is the same, which is done with the option same_xy'. (%i1) plot2d([[parametric, cos(t), sin(t), [t,0,2*%pi]], -abs(x)], [x, -sqrt(2), sqrt(2)], same_xy)$

A plot of 200 random numbers between 0 and 9:

(%i1) plot2d ([discrete, makelist ( random(10), 200)])$A plot of a discrete set of points, defining x and y coordinates separately: (%i1) plot2d ([discrete, makelist(i*%pi, i, 1, 5), [0.6, 0.9, 0.2, 1.3, 1]])$

In the next example a table with three columns is saved in a file
"data.txt" which is then read and the second and third column are
plotted on the two axes:

(%i1) with_stdout ("data.txt", for x:0 thru 10 do
print (x, x^2, x^3))$(%i2) data: read_matrix ("data.txt")$
(%i3) plot2d ([discrete, transpose(data), transpose(data)],
[style,points], [point_type,diamond], [color,red])$A plot of discrete data points together with a continuous function: (%i1) xy: [[10, .6], [20, .9], [30, 1.1], [40, 1.3], [50, 1.4]]$
(%i2) plot2d([[discrete, xy], 2*%pi*sqrt(l/980)], [l,0,50],
[style, points, lines], [color, red, blue],
[point_type, asterisk],
[legend, "experiment", "theory"],
[xlabel, "pendulum's length (cm)"],
[ylabel, "period (s)"])$See also the section about Plotting Options.  Function: plot3d   plot3d (<expr>, <x_range>, <y_range>, ..., <options>, ...) plot3d ([<expr_1>, ..., <expr_n>], <x_range>, <y_range>, ..., <options>, ...) Displays a plot of one or more surfaces defined as functions of two variables or in parametric form. The functions to be plotted may be specified as expressions or function names. The mouse can be used to rotate the plot looking at the surface from different sides. *Examples:* Plot of a function of two variables: (%i1) plot3d (u^2 - v^2, [u, -2, 2], [v, -3, 3], [grid, 100, 100], [mesh_lines_color,false])$

Use of the z' option to limit a function that goes to infinity
(in this case the function is minus infinity on the x and y axes);
this also shows how to plot with only lines and no shading:

(%i1) plot3d ( log ( x^2*y^2 ), [x, -2, 2], [y, -2, 2], [z, -8, 4],
[palette, false], [color, magenta])$The infinite values of z can also be avoided by choosing a grid that does not fall on any points where the function is undefined, as in the next example, which also shows how to change the palette and how to include a color bar that relates colors to values of the z variable: (%i1) plot3d (log (x^2*y^2), [x, -2, 2], [y, -2, 2],[grid, 29, 29], [palette, [gradient, red, orange, yellow, green]], color_bar, [xtics, 1], [ytics, 1], [ztics, 4], [color_bar_tics, 4])$

Two surfaces in the same plot. Ranges specific to one of the
surfaces can be given by placing each expression and its ranges in
a separate list; global ranges for the complete plot are also
given after the functions definitions.

(%i1) plot3d ([[-3*x - y, [x, -2, 2], [y, -2, 2]],
4*sin(3*(x^2 + y^2))/(x^2 + y^2), [x, -3, 3], [y, -3, 3]],
[x, -4, 4], [y, -4, 4])$Plot of a Klein bottle, defined parametrically: (%i1) expr_1: 5*cos(x)*(cos(x/2)*cos(y)+sin(x/2)*sin(2*y)+3)-10$
(%i2) expr_2: -5*sin(x)*(cos(x/2)*cos(y)+sin(x/2)*sin(2*y)+3)$(%i3) expr_3: 5*(-sin(x/2)*cos(y)+cos(x/2)*sin(2*y))$
(%i4) plot3d ([expr_1, expr_2, expr_3], [x, -%pi, %pi],
[y, -%pi, %pi], [grid, 50, 50])$Plot of a "spherical harmonic" function, using the predefined transformation, spherical_to_xyz' to transform from spherical coordinates to rectangular coordinates. See the documentation for spherical_to_xyz'. (%i1) plot3d (sin(2*theta)*cos(phi), [theta, 0, %pi], [phi, 0, 2*%pi], [transform_xy, spherical_to_xyz], [grid,30,60], [legend,false])$

Use of the pre-defined function polar_to_xy' to transform from
cylindrical to rectangular coordinates.  See the documentation for
polar_to_xy'.

(%i1) plot3d (r^.33*cos(th/3), [r,0,1], [th,0,6*%pi], [box, false],
[grid, 12, 80], [transform_xy, polar_to_xy], [legend, false])$Plot of a sphere using the transformation from spherical to rectangular coordinates. Option same_xyz' is used to get the three axes scaled in the same proportion. When transformations are used, it is not convenient to eliminate the mesh lines, because Gnuplot will not show the surface correctly. (%i1) plot3d ( 5, [theta, 0, %pi], [phi, 0, 2*%pi], same_xyz, [transform_xy, spherical_to_xyz], [mesh_lines_color,blue], [palette,[gradient,"#1b1b4e", "#8c8cf8"]], [legend, false])$

Definition of a function of two-variables using a matrix.  Notice
the single quote in the definition of the function, to prevent
plot3d' from failing when it realizes that the matrix will
require integer indices.

(%i1) M: matrix([1,2,3,4], [1,2,3,2], [1,2,3,4], [1,2,3,3])$(%i2) f(x, y) := float('M [round(x), round(y)])$
(%i3) plot3d (f(x,y), [x,1,4],[y,1,4],[grid,3,3],[legend,false])$By setting the elevation equal to zero, a surface can be seen as a map in which each color represents a different level. (%i1) plot3d (cos (-x^2 + y^3/4), [x,-4,4], [y,-4,4], [zlabel,""], [mesh_lines_color,false], [elevation,0], [azimuth,0], color_bar, [grid,80,80], [ztics,false], [color_bar_tics,1])$


System variable: plot_options

     This option is being kept for compatibility with older versions,
but its use is deprecated. To set global plotting options, see
their current values or remove options, use set_plot_option',
get_plot_option' and remove_plot_option'.


Function: remove_plot_option (<name>)

     Removes the default value of an option. The name of the option
must be given.

See also set_plot_option', get_plot_option' and the section on
Plotting Options.


Function: set_plot_option (<option>)

     Accepts any of the options listed in the section Plotting Options,
and saves them for use in plotting commands. The values of the
options set in each plotting command will have precedence, but if
those options are not given, the default values set with this
function will be used.

set_plot_option' evaluates its argument and returns the complete
list of options (after modifying the option given). If called
without any arguments, it will simply show the list of current
default options.

See also remove_plot_option', get_plot_option' and the section
on Plotting Options.

Example:

Modification of the grid' values.

(%i1) set_plot_option ([grid, 30, 40]);
(%o1) [[plot_format, gnuplot_pipes], [grid, 30, 40],
[run_viewer, true], [axes, true], [nticks, 29], [adapt_depth, 5],
[color, blue, red, green, magenta, black, cyan],
[point_type, bullet, box, triangle, plus, times, asterisk],
[palette, [gradient, green, cyan, blue, violet],
[gradient, magenta, violet, blue, cyan, green, yellow, orange,
red, brown, black]], [gnuplot_preamble, ], [gnuplot_term, default]]


System function: spherical_to_xyz

     It can be given as value for the transform_xy' option of
plot3d'. Its effect will be to interpret the two independent
variables and the function in plot3d' as the spherical coordinates
of a point (first, the angle with the z axis, then the angle of
the xy projection with the x axis and finally the distance from
the origin) and transform them into x, y and z coordinates.



## 12.4 Plotting Options

All options consist of a list starting with one of the keywords in this
section, followed by one or more values. Some of the options may have
different effects in different plotting commands as it will be pointed
out in the following list. The options that accept among their possible
values true or false, can also be set to true by simply writing their
names. For instance, typing logx as an option is equivalent to writing
[logx, true].

Plot option: adapt_depth [adapt_depth, <integer>]

     Default value: 5'

The maximum number of splittings used by the adaptive plotting
routine.


Plot option: axes [axes, <symbol>]

     Default value: true'

Where <symbol> can be either true', false', x', y' or solid'.
If false', no axes are shown; if equal to x' or y' only the x
or y axis will be shown; if it is equal to true', both axes will
be shown and solid' will show the two axes with a solid line,
rather than the default broken line. This option does not have any
effect in the 3 dimensional plots.


Plot option: azimuth [azimuth, <number>]

     Default value: 30'

A plot3d plot can be thought of as starting with the x and y axis
in the horizontal and vertical axis, as in plot2d, and the z axis
coming out of the screen.  The z axis is then rotated around the x
axis through an angle equal to elevation' and then the new xy
plane is rotated around the new z axis through an angle azimuth'.
This option sets the value for the azimuth, in degrees.


Plot option: box [box, <symbol>]

     Default value: true'

If set to true', a bounding box will be drawn for the plot; if set
to false', no box will be drawn.


Plot option: color [color, <color_1>, ..., <color_n>]

     In 2d plots it defines the color (or colors) for the various
curves.  In plot3d', it defines the colors used for the mesh
lines of the surfaces, when no palette is being used.

If there are more curves or surfaces than colors, the colors will
be repeated in sequence. The valid colors are red', green',
blue', magenta', cyan', yellow', orange', violet', brown',
gray', black', white', or a string starting with the character
# and followed by six hexadecimal digits: two for the red
component, two for green component and two for the blue component.
If the name of a given color is unknown color, black will be used


Plot option: color_bar [color_bar, <symbol>]

     Default value: false' in plot3d, true' in mandelbrot and julia

Where <symbol> can be either true' or false'.  If true',
whenever plot3d', mandelbrot' or julia' use a palette to
represent different values, a box will be shown on the right,
showing the corresponding between colors and values.


Plot option: color_bar_tics [color_bar_tics, <x1>, <x2>, <x3>]

     Defines the values at which a mark and a number will be placed in
the color bar. The first number is the initial value, the second
the increments and the third is the last value where a mark is
placed. The second and third numbers can be omitted. When only one
number is given, it will be used as the increment from an initial
value that will be chosen automatically.


Plot option: elevation [elevation, <number>]

     Default value: 60'

A plot3d plot can be thought of as starting with the x and y axis
in the horizontal and vertical axis, as in plot2d, and the z axis
coming out of the screen.  The z axis is then rotated around the x
axis through an angle equal to elevation' and then the new xy
plane is rotated around the new z axis through an angle azimuth'.
This option sets the value for the azimuth, in degrees.


Plot option: grid [grid, <integer>, <integer>]

     Default value: 30', 30'

Sets the number of grid points to use in the x- and y-directions
for three-dimensional plotting or for the julia' and mandelbrot'
programs.


Plot option: grid2d [grid, <value>]

     Default value: false'

Shows a grid of lines on the xy plane. The points where the grid
lines are placed are the same points where tics are marked in the
x and y axes, which can be controlled with the xtics' and ytics'
options.


Plot option: iterations [grid, <value>]

     Default value: 9'

Number of iterations made by the programs mandelbrot and julia.


Plot option: label [label, [<string>, <x>, <y>], ...]

     Writes one or several labels in the points with <x>, <y>
coordinates indicated after each label.


Plot option: legend

          legend [legend, <string_1>, ..., <string_n>]
legend [legend, <false>]
It specifies the labels for the plots when various plots are
shown.  If there are more plots than the number of labels given,
they will be repeated.  If given the value false', no legends
will be shown.  By default, the names of the expressions or
functions will be used, or the words discrete1, discrete2, ...,
for discrete sets of points.


Plot option: logx [logx, <value>]

     Makes the horizontal axes to be scaled logarithmically. It can be
either true or false.


Plot option: logy [logy, <value>]

     Makes the vertical axes to be scaled logarithmically. It can be
either true or false.


Plot option: mesh_lines_color [mesh_lines_color, <color>]

     Default value: black'

It sets the color used by plot3d to draw the mesh lines, when a
palette is being used.  It accepts the same colors as for the
option color' (see the list of allowed colors in color').  It
can also be given a value false' to eliminate completely the mesh
lines.


Plot option: nticks [nticks, <integer>]

     Default value: 29'

When plotting functions with plot2d', it is gives the initial
number of points used by the adaptive plotting routine for plotting
functions.  When plotting parametric functions with plot3d', it
sets the number of points that will be shown for the plot.


Plot option: palette

          palette [palette, [<palette_1>], ..., [<palette_n>]]
palette [palette, <false>]
It can consist of one palette or a list of several palettes.  Each
palette is a list with a keyword followed by values. If the
keyword is gradient, it should be followed by a list of valid
colors.

If the keyword is hue, saturation or value, it must be followed by
4 numbers. The first three numbers, which must be between 0 and 1,
define the hue, saturation and value of a basic color to be
assigned to the minimum value of z. The keyword specifies which of
the three attributes (hue, saturation or value) will be increased
according to the values of z.  The last number indicates the
increase corresponding to the maximum value of z.  That last
number can be bigger than 1 or negative; the corresponding values
of the modified attribute will be rounded modulo 1.

Gnuplot only uses the first palette in the list; xmaxima will use
the palettes in the list sequentially, when several surfaces are
plotted together; if the number of palettes is exhausted, they
will be repeated sequentially.

The color of the mesh lines will be given by the option
mesh_lines_color'.  If palette' is given the value false', the
surfaces will not be shaded but represented with a mesh of curves
only.  In that case, the colors of the lines will be determined by
the option color'.


Plot option: plot_format [plot_format, <format>]

     Default value: gnuplot', in Windows systems, or gnuplot_pipes' in
other systems.

Where <format> is one of the following: gnuplot, xmaxima, mgnuplot
or gnuplot_pipes.

It sets the format to be used for plotting.


Plot option: plot_realpart [plot_realpart, <symbol>]

     Default value: false'

If set to true', the functions to be plotted will be considered
as complex functions whose real value should be plotted; this is
equivalent to plotting realpart(<function>)'.  If set to false',
nothing will be plotted when the function does not give a real
value.  For instance, when x' is negative, log(x)' gives a
complex value, with real value equal to log(abs(x))'; if
plot_realpart' were true', log(-5)' would be plotted as
log(5)', while nothing would be plotted if plot_realpart' were
false'.


Plot option: point_type [point_type, <type_1>, ..., <type_n>]

     In gnuplot, each set of points to be plotted with the style
"points" or "linespoints" will be represented with objects taken
from this list, in sequential order.  If there are more sets of
points than objects in this list, they will be repeated
sequentially.  The possible objects that can be used are:
bullet', circle', plus', times', asterisk', box', square',
triangle', delta', wedge', nabla', diamond', lozenge'.


Plot option: pdf_file [pdf_file, <file_name>]

     Saves the plot into a PDF file with name equal to <file_name>,
rather than showing it in the screen.  By default, the file will be
created in the directory defined by the variable maxima_tempdir',
unless <file_name> contains the character "/", in which case it
will be assumed to contain the complete path where the file should
be created. The value of maxima_tempdir' can be changed to save
the file in a different directory. When the option
gnuplot_pdf_term_command' is also given, it will be used to set up
Gnuplot's PDF terminal; otherwise, Gnuplot's pdfcairo terminal
will be used with solid colored lines of width 3, plot size of
17.2 cm by 12.9 cm and font of 18 points.


Plot option: png_file [png_file, <file_name>]

     Saves the plot into a PNG graphics file with name equal to
<file_name>, rather than showing it in the screen. By default, the
file will be created in the directory defined by the variable
maxima_tempdir', unless <file_name> contains the character "/",
in which case it will be assumed to contain the complete path where
the file should be created. The value of maxima_tempdir' can be
changed to save the file in a different directory. When the option
gnuplot_png_term_command' is also given, it will be used to set up
Gnuplot's PNG terminal; otherwise, Gnuplot's pngcairo terminal
will be used, with a font of size 12.


Plot option: ps_file [ps_file, <file_name>]

     Saves the plot into a Postscript file with name equal to
<file_name>, rather than showing it in the screen.  By default,
the file will be created in the directory defined by the variable
maxima_tempdir', unless <file_name> contains the character "/",
in which case it will be assumed to contain the complete path where
the file should be created. The value of maxima_tempdir' can be
changed to save the file in a different directory. When the option
gnuplot_ps_term_command' is also given, it will be used to set up
Gnuplot's Postscript terminal; otherwise, Gnuplot's postscript
terminal will be used with the EPS option, solid colored lines of
width 2, plot size of 16.4 cm by 12.3 cm and font of 24 points.


Plot option: run_viewer [run_viewer, <symbol>]

     This option is only used when the plot format is gnuplot' and the
terminal is default' or when the Gnuplot terminal is set to
dumb' (see gnuplot_term') and can have a true or false value.

If the terminal is default', a file maxout.gnuplot' (or other
name specified with gnuplot_out_file') is created with the
gnuplot commands necessary to generate the plot. Option
run_viewer' controls whether or not Gnuplot will be launched to
execute those commands and show the plot.

If the terminal is default', gnuplot is run to execute the
commands in maxout.gnuplot', producing another file maxplot.txt'
(or other name specified with gnuplot_out_file'). Option
run_viewer' controls whether or not that file, with an ASCII
representation of the plot, will be shown in the Maxima or Xmaxima
console.

The default value for this option is true, making the plots to be
shown in either the console or a separate graphics window.


Plot option: same_xy [same_xy , <value>]

     It can be either true or false. If true, the scales used in the x
and y axes will be the same, in either 2d or 3d plots. See also
yx_ratio'.


Plot option: same_xyz [same_xyz , <value>]

     It can be either true or false. If true, the scales used in the 3
axes of a 3d plot will be the same.


Plot option: style

          style [style, <type_1>, ..., <type_n>]
style [style, [<style_1>], ..., [<style_n>]]
The styles that will be used for the various functions or sets of
data in a 2d plot.  The word <style> must be followed by one or
more styles.  If there are more functions and data sets than the
styles given, the styles will be repeated.  Each style can be
either <lines> for line segments, <points> for isolated points,
<linespoints> for segments and points, or <dots> for small
isolated dots.  Gnuplot accepts also an <impulses> style.

Each of the styles can be enclosed inside a list with some
additional parameters.  <lines> accepts one or two numbers: the
width of the line and an integer that identifies a color.  The
default color codes are: 1: blue, 2: red, 3: magenta, 4: orange,
5: brown, 6: lime and 7: aqua.  If you use Gnuplot with a terminal
different than X11, those colors might be different; for example,
if you use the option [<gnuplot_term>, <ps>], color index 4 will
correspond to black, instead of orange.

<points> accepts one two or three parameters; the first parameter
is the radius of the points, the second parameter is an integer
that selects the color, using the same code used for <lines> and
the third parameter is currently used only by Gnuplot and it
corresponds to several objects instead of points.  The default
types of objects are: 1: filled circles, 2: open circles, 3: plus
signs, 4: x, 5: *, 6: filled squares, 7: open squares, 8: filled
triangles, 9: open triangles, 10: filled inverted triangles, 11:
open inverted triangles, 12: filled lozenges and 13: open lozenges.

<linespoints> accepts up to four parameters: line width, points
radius, color and type of object to replace the points.

See also color' and point_type'.


Plot option: svg_file [svg_file, <file_name>]

     Saves the plot into an SVG file with name equal to <file_name>,
rather than showing it in the screen.  By default, the file will be
created in the directory defined by the variable maxima_tempdir',
unless <file_name> contains the character "/", in which case it
will be assumed to contain the complete path where the file should
be created. The value of maxima_tempdir' can be changed to save
the file in a different directory. When the option
gnuplot_svg_term_command' is also given, it will be used to set up
Gnuplot's SVG terminal; otherwise, Gnuplot's svg terminal will be
used with font of 14 points.


Plot option: t [t, <min>, <max>]

     Default range for parametric plots.


Plot option: title [title, <text>]

     Defines a title that will be written at the top of the plot.


Plot option: transform_xy [transform_xy, <symbol>]

     Where <symbol> is either false' or the result obtained by using
the function transform_xy'.  If different from false', it will
be used to transform the 3 coordinates in plot3d.

See make_transform', polar_to_xy' and spherical_to_xyz'.


Plot option: x [x, <min>, <max>]

     When used as the first option in a plot2d' command (or any of the
first two in plot3d'), it indicates that the first independent
variable is x and it sets its range.  It can also be used again
after the first option (or after the second option in plot3d) to
define the effective horizontal domain that will be shown in the
plot.


Plot option: xlabel [xlabel, <string>]

     Specifies the <string> that will label the first axis; if this
option is not used, that label will be the name of the independent
variable, when plotting functions with plot2d' or
implicit_plot', or the name of the first variable, when plotting
surfaces with plot3d' or contours with contour_plot', or the
first expression in the case of a parametric plot.  It can not be
used with set_plot_option'.


Plot option: xtics [xtics, <x1>, <x2>, <x3>]

     Defines the values at which a mark and a number will be placed in
the x axis. The first number is the initial value, the second the
increments and the third is the last value where a mark is placed.
The second and third numbers can be omitted. When only one number
is given, it will be used as the increment from an initial value
that will be chosen automatically.


Plot option: xy_scale [xy_scale, <sx>, <sy>]

     In a 2d plot, it defines the ratio of the total size of the Window
to the size that will be used for the plot. The two numbers given
as arguments are the scale factors for the x and y axes.


Plot option: y [y, <min>, <max>]

     When used as one of the first two options in plot3d', it indicates
that one of the independent variables is y and it sets its range.
Otherwise, it defines the effective domain of the second variable
that will be shown in the plot.


Plot option: ylabel [ylabel, <string>]

     Specifies the <string> that will label the second axis; if this
option is not used, that label will be "y", when plotting functions
with plot2d' or implicit_plot', or the name of the second
variable, when plotting surfaces with plot3d' or contours with
contour_plot', or the second expression in the case of a
parametric plot.  It can not be used with set_plot_option'.


Plot option: ytics [ytics, <y1>, <y2>, <y3>]

     Defines the values at which a mark and a number will be placed in
the y axis. The first number is the initial value, the second the
increments and the third is the last value where a mark is placed.
The second and third numbers can be omitted. When only one number
is given, it will be used as the increment from an initial value
that will be chosen automatically


Plot option: yx_ratio [yx_ratio, <r>]

     In a 2d plot, the ratio between the vertical and the horizontal
sides of the rectangle used to make the plot. See also same_xy'.


Plot option: z [z, <min>, <max>]

     Used in plot3d' to set the effective range of values of z that
will be shown in the plot.


Plot option: zlabel [zlabel, <string>]

     Specifies the <string> that will label the third axis, when using
plot3d'.  If this option is not used, that label will be "z", when
plotting surfaces, or the third expression in the case of a
parametric plot.  It can not be used with set_plot_option' and it
will be ignored by plot2d' and implicit_plot'.


Plot option: zmin [zmin, <z>]

     In 3d plots, the value of z that will be at the bottom of the plot
box.



## 12.5 Gnuplot Options

There are several plot options specific to gnuplot.  All of them consist
of a keyword (the name of the option), followed by a string that should
be a valid gnuplot command, to be passed directly to gnuplot.  In most
cases, there exist a corresponding plotting option that will produce a
similar result and whose use is more recommended than the gnuplot
specific option.

Plot option: gnuplot_term [gnuplot_term, <terminal_name>]

     Sets the output terminal type for gnuplot. The argument
<terminal_name> can be a string or one of the following 3 special
symbols
* *default* (default value)

Gnuplot output is displayed in a separate graphical window
and the gnuplot terminal used will be specified by the value
of the option gnuplot_default_term_command'.

* *dumb*

Gnuplot output is saved to a file maxout.gnuplot' using
"ASCII art" approximation to graphics. If the option
gnuplot_out_file' is set to <filename>, the plot will be
saved there, instead of the default maxout.gnuplot'. The
settings for the "dumb" terminal of Gnuplot are given by the
value of option gnuplot_dumb_term_command'. If option
run_viewer' is set to true and the plot_format is gnuplot'
that ASCII representation will also be shown in the Maxima or
Xmaxima console.

* *ps*

Gnuplot generates commands in the PostScript page description
language.  If the option gnuplot_out_file' is set to
<filename>, gnuplot writes the PostScript commands to
<filename>.  Otherwise, it is saved as maxplot.ps' file. The
settings for this terminal are given by the value of the
option gnuplot_dumb_term_command'.

* A string representing any valid gnuplot term specification

Gnuplot can generate output in many other graphical formats
such as png, jpeg, svg etc. To use those formats, option
gnuplot_term' can be set to any supported gnuplot term name
(which must be a symbol) or even a full gnuplot term
specification with any valid options (which must be a
string).  For example [gnuplot_term, png]' creates output in
PNG (Portable Network Graphics) format while [gnuplot_term,
"png size 1000,1000"]' creates PNG of 1000 x 1000 pixels
size.  If the option gnuplot_out_file' is set to <filename>,
gnuplot writes the output to <filename>.  Otherwise, it is
saved as maxplot.<term>' file, where <term> is gnuplot
terminal name.


Plot option: gnuplot_out_file [gnuplot_out_file, <file_name>]

     It can be used to replace the default name for the file that
contains the commands that will interpreted by gnuplot, when the
terminal is set to default', or to replace the default name of
the graphic file that gnuplot creates, when the terminal is
different from default'. If it contains one or more slashes, "/",
the name of the file will be left as it is; otherwise, it will be
appended to the path of the temporary directory. The complete name
of the files created by the plotting commands is always sent as
output of those commands so they can be seen if the command is
ended by semi-colon.

When used in conjunction with the gnuplot_term' option, it can be
used to save the plot in a file, in one of the graphic formats
supported by Gnuplot. To create PNG, PDF, Postscript or SVG, it is
easier to use options png_file', pdf_file', ps_file', or
svg_file'.


Plot option: gnuplot_pm3d [gnuplot_pm3d, <value>]

     With a value of false', it can be used to disable the use of PM3D
mode, which is enabled by default.


Plot option: gnuplot_preamble [gnuplot_preamble, <string>]

     This option inserts gnuplot commands before any other commands
sent to Gnuplot. Any valid gnuplot commands may be used. Multiple
gnuplot_postamble'.


Plot option: gnuplot_postamble [gnuplot_postamble, <string>]

     This option inserts gnuplot commands after other commands sent to
Gnuplot and right before the plot command is sent. Any valid
gnuplot commands may be used. Multiple commands should be


Plot option: gnuplot_default_term_command

     [gnuplot_default_term_command, <command>]

The gnuplot command to set the terminal type for the default
terminal. It this option is not set, the command used will be:
"set term wxt size 640,480 font \",12\"; set term pop"'.


Plot option: gnuplot_dumb_term_command

     [gnuplot_dumb_term_command, <command>]

The gnuplot command to set the terminal type for the dumb
terminal.  It this option is not set, the command used will be:
"set term dumb 79 22"', which makes the text output 79 characters
by 22 characters.


Plot option: gnuplot_pdf_term_command [gnuplot_pdf_term_command, <command>]

     The gnuplot command to set the terminal type for the PDF terminal.
If this option is not set, the command used will be: "set term
pdfcairo color solid lw 3 size 17.2 cm, 12.9 cm font \",18\""'.


Plot option: gnuplot_png_term_command [gnuplot_png_term_command, <command>]

     The gnuplot command to set the terminal type for the PNG terminal.
If this option is not set, the command used will be: "set term
pngcairo font \",12\""'. See the gnuplot documentation for more
information.


Plot option: gnuplot_ps_term_command [gnuplot_ps_term_command, <command>]

     The gnuplot command to set the terminal type for the PostScript
terminal.  If this option is not set, the command used will be:
"set term postscript eps color solid lw 2 size 16.4 cm, 12.3 cm
font \",24\""'. See the gnuplot documentation for set term


Plot option: gnuplot_svg_term_command [gnuplot_svg_term_command, <command>]

     The gnuplot command to set the terminal type for the SVG terminal.
If this option is not set, the command used will be: "set term
svg font \",14\""'. See the gnuplot documentation for more
information.


Plot option: gnuplot_curve_titles

     This is an obsolete option that has been replaced legend'
described above.


Plot option: gnuplot_curve_styles

     This is an obsolete option that has been replaced by style'.



## 12.6 Gnuplot_pipes Format Functions

Function: gnuplot_start ()

     Opens the pipe to gnuplot used for plotting with the
gnuplot_pipes' format.  Is not necessary to manually open the
pipe before plotting.


Function: gnuplot_close ()

     Closes the pipe to gnuplot which is used with the gnuplot_pipes'
format.


Function: gnuplot_restart ()

     Closes the pipe to gnuplot which is used with the gnuplot_pipes'
format and opens a new pipe.


Function: gnuplot_replot

          gnuplot_replot ()
gnuplot_replot (<s>)
Updates the gnuplot window.  If gnuplot_replot' is called with a
gnuplot command in a string <s>, then s' is sent to gnuplot
before reploting the window.


Function: gnuplot_reset ()

     Resets the state of gnuplot used with the gnuplot_pipes' format.
To update the gnuplot window call gnuplot_replot' after
gnuplot_reset'.



## 13 File Input and Output


Files
Functions and Variables for File Input and Output
Functions and Variables for TeX Output
Functions and Variables for Fortran Output


A comment in Maxima input is any text between /*' and */'.

The Maxima parser treats a comment as whitespace for the purpose of
finding tokens in the input stream; a token always ends at a comment.
An input such as a/* foo */b' contains two tokens, a' and b', and
not a single token ab'.  Comments are otherwise ignored by Maxima;
neither the content nor the location of comments is stored in parsed
input expressions.

Comments can be nested to arbitrary depth.  The /*' and */'
delimiters form matching pairs.  There must be the same number of /*'
as there are */'.

Examples:

(%i1) /* aa is a variable of interest */  aa : 1234;
(%o1)                         1234
(%i2) /* Value of bb depends on aa */  bb : aa^2;
(%o2)                        1522756
(%i3) /* User-defined infix operator */  infix ("b");
(%o3)                           b
(%i4) /* Parses same as a b c, not abc */  a/* foo */b/* bar */c;
(%o4)                         a b c
(%i5) /* Comments /* can be nested /* to any depth */ */ */  1 + xyz;
(%o5)                        xyz + 1


## 13.2 Files

A file is simply an area on a particular storage device which contains
data or text.  Files on the disks are figuratively grouped into
"directories".  A directory is just a list of files.  Commands which
deal with files are:

closefile            file_output_append    filename_merge
file_search          file_search_maxima    file_search_lisp
file_search_demo     file_search_usage     file_search_tests
file_type            file_type_lisp        file_type_maxima
pathname_type        printfile             save
stringout            with_stdout           writefile

When a file name is passed to functions like plot2d', save', or
writefile' and the file name does not include a path, Maxima stores
the file in the current working directory.  The current working
directory depends on the system like Windows or Linux and on the
installation.


## 13.3 Functions and Variables for File Input and Output

Function: appendfile (<filename>)

     Appends a console transcript to <filename>.  appendfile' is the
same as writefile', except that the transcript file, if it
exists, is always appended.

closefile' closes the transcript file opened by appendfile' or
writefile'.


Function: batch

          batch (<filename>)
batch (<filename>, option')
batch(<filename>)' reads Maxima expressions from <filename> and
evaluates them.  batch' searches for <filename> in the list
file_search_maxima'.  See also file_search'.

batch(<filename>, demo')' is like demo(<filename>)'.  In this
case batch' searches for <filename> in the list
file_search_demo'.  See demo'.

batch(<filename>, test')' is like run_testsuite' with the
option display_all=true'.  For this case batch' searches
<filename> in the list file_search_maxima' and not in the list
file_search_tests' like run_testsuite'.  Furthermore,
run_testsuite' runs tests which are in the list
testsuite_files'.  With batch' it is possible to run any file in
a test mode, which can be found in the list file_search_maxima'.
This is useful, when writing a test file.

<filename> comprises a sequence of Maxima expressions, each
terminated with ;' or $'. The special variable %' and the function %th' refer to previous results within the file. The file may include :lisp' constructs. Spaces, tabs, and newlines in the file are ignored. A suitable input file may be created by a text editor or by the stringout' function. batch' reads each input expression from <filename>, displays the input to the console, computes the corresponding output expression, and displays the output expression. Input labels are assigned to the input expressions and output labels are assigned to the output expressions. batch' evaluates every input expression in the file unless there is an error. If user input is requested (by asksign' or askinteger', for example) batch' pauses to collect the requisite input and then continue. It may be possible to halt batch' by typing control-C' at the console. The effect of control-C' depends on the underlying Lisp implementation. batch' has several uses, such as to provide a reservoir for working command lines, to give error-free demonstrations, or to help organize one's thinking in solving complex problems. batch' evaluates its argument. batch' returns the path of <filename> as a string, when called with no second argument or with the option demo'. When called with the option test', the return value is a an empty list []' or a list with <filename> and the numbers of the tests which have failed. See also load', batchload', and demo'.  Function: batchload (<filename>)   Reads Maxima expressions from <filename> and evaluates them, without displaying the input or output expressions and without assigning labels to output expressions. Printed output (such as produced by print' or describe')) is displayed, however. The special variable %' and the function %th' refer to previous results from the interactive interpreter, not results within the file. The file cannot include :lisp' constructs. batchload' returns the path of <filename>, as a string. batchload' evaluates its argument. See also batch', and load'.  Function: closefile ()   Closes the transcript file opened by writefile' or appendfile'.  Option variable: file_output_append   Default value: false' file_output_append' governs whether file output functions append or truncate their output file. When file_output_append' is true', such functions append to their output file. Otherwise, the output file is truncated. save', stringout', and with_stdout' respect file_output_append'. Other functions which write output files do not respect file_output_append'. In particular, plotting and translation functions always truncate their output file, and tex' and appendfile' always append.  Function: filename_merge (<path>, <filename>)   Constructs a modified path from <path> and <filename>. If the final component of <path> is of the form ###.<something>', the component is replaced with <filename>.<something>'. Otherwise, the final component is simply replaced by <filename>. The result is a Lisp pathname object.  Function: file_search   file_search (<filename>) file_search (<filename>, <pathlist>) file_search' searches for the file <filename> and returns the path to the file (as a string) if it can be found; otherwise file_search' returns false'. file_search (<filename>)' searches in the default search directories, which are specified by the file_search_maxima', file_search_lisp', and file_search_demo' variables. file_search' first checks if the actual name passed exists, before attempting to match it to "wildcard" file search patterns. See file_search_maxima' concerning file search patterns. The argument <filename> can be a path and file name, or just a file name, or, if a file search directory includes a file search pattern, just the base of the file name (without an extension). For example, file_search ("/home/wfs/special/zeta.mac"); file_search ("zeta.mac"); file_search ("zeta"); all find the same file, assuming the file exists and /home/wfs/special/###.mac' is in file_search_maxima'. file_search (<filename>, <pathlist>)' searches only in the directories specified by <pathlist>, which is a list of strings. The argument <pathlist> supersedes the default search directories, so if the path list is given, file_search' searches only the ones specified, and not any of the default search directories. Even if there is only one directory in <pathlist>, it must still be given as a one-element list. The user may modify the default search directories. See file_search_maxima'. file_search' is invoked by load' with file_search_maxima' and file_search_lisp' as the search directories.  Option variable: file_search_maxima  Option variable: file_search_lisp  Option variable: file_search_demo  Option variable: file_search_usage  Option variable: file_search_tests   These variables specify lists of directories to be searched by load', demo', and some other Maxima functions. The default values of these variables name various directories in the Maxima installation. The user can modify these variables, either to replace the default values or to append additional directories. For example, file_search_maxima: ["/usr/local/foo/###.mac", "/usr/local/bar/###.mac"]$

replaces the default value of file_search_maxima', while

file_search_maxima: append (file_search_maxima,
["/usr/local/foo/###.mac", "/usr/local/bar/###.mac"])$appends two additional directories. It may be convenient to put such an expression in the file maxima-init.mac' so that the file search path is assigned automatically when Maxima starts. See also *note Introduction for Runtime Environment::. Multiple filename extensions and multiple paths can be specified by special "wildcard" constructions. The string ###' expands into the sought-after name, while a comma-separated list enclosed in curly braces {foo,bar,baz}' expands into multiple strings. For example, supposing the sought-after name is neumann', "/home/{wfs,gcj}/###.{lisp,mac}" expands into /home/wfs/neumann.lisp', /home/gcj/neumann.lisp', /home/wfs/neumann.mac', and /home/gcj/neumann.mac'.  Function: file_type (<filename>)   Returns a guess about the content of <filename>, based on the filename extension. <filename> need not refer to an actual file; no attempt is made to open the file and inspect the content. The return value is a symbol, either object', lisp', or maxima'. If the extension is matches one of the values in file_type_maxima', file_type' returns maxima'. If the extension matches one of the values in file_type_lisp', file_type' returns lisp'. If none of the above, file_type' returns object'. See also pathname_type'. See file_type_maxima' and file_type_lisp' for the default values. Examples: (%i2) map('file_type, ["test.lisp", "test.mac", "test.dem", "test.txt"]); (%o2) [lisp, maxima, maxima, object]  Option variable: file_type_lisp   Default value: [l, lsp, lisp]' file_type_lisp' is a list of file extensions that maxima recognizes as denoting a Lisp source file. See also file_type'.  Option variable: file_type_maxima   Default value: [mac, mc, demo, dem, dm1, dm2, dm3, dmt]' file_type_maxima' is a list of file extensions that maxima recognizes as denoting a Maxima source file. See also file_type'.  Function: load (<filename>)   Evaluates expressions in <filename>, thus bringing variables, functions, and other objects into Maxima. The binding of any existing object is clobbered by the binding recovered from <filename>. To find the file, load' calls file_search' with file_search_maxima' and file_search_lisp' as the search directories. If load' succeeds, it returns the name of the file. Otherwise load' prints an error message. load' works equally well for Lisp code and Maxima code. Files created by save', translate_file', and compile_file', which create Lisp code, and stringout', which creates Maxima code, can all be processed by load'. load' calls loadfile' to load Lisp files and batchload' to load Maxima files. load' does not recognize :lisp' constructs in Maxima files, and while processing <filename>, the global variables _', __', %', and %th' have whatever bindings they had when load' was called. See also loadfile', batch', batchload', and demo'. loadfile' processes Lisp files; batch', batchload', and demo' process Maxima files. See file_search' for more detail about the file search mechanism. load' evaluates its argument.  System variable: load_pathname   Default value: false' When a file is loaded with the functions load', loadfile' or batchload' the system variable load_pathname' is bound to the pathname of the file which is processed. The variable load_pathname' can be accessed from the file during the loading. Example: Suppose we have a batchfile test.mac' in the directory "/home/dieter/workspace/mymaxima/temp/"' with the following commands print("The value of load_pathname is: ", load_pathname)$
print("End of batchfile")$then we get the following output (%i1) load("/home/dieter/workspace/mymaxima/temp/test.mac")$
/home/dieter/workspace/mymaxima/temp/test.mac
End of batchfile


Function: loadfile (<filename>)

     Evaluates Lisp expressions in <filename>.  loadfile' does not
invoke file_search', so filename' must include the file
extension and as much of the path as needed to find the file.

loadfile' can process files created by save', translate_file',
and compile_file'.  The user may find it more convenient to use
load' instead of loadfile'.


Option variable: loadprint

     Default value: true'

loadprint' tells whether to print a message when a file is loaded.

* When loadprint' is true', always print a message.

* When loadprint' is 'loadfile', print a message only if a

* When loadprint' is 'autoload', print a message only if a
file is automatically loaded.  See setup_autoload'.

* When loadprint' is false', never print a message.


Function: pathname_directory (<pathname>)

Function: pathname_name (<pathname>)

Function: pathname_type (<pathname>)

     These functions return the components of <pathname>.

Examples:

(%i1) pathname_directory("/home/dieter/maxima/changelog.txt");
(%o1)                 /home/dieter/maxima/
(%i2) pathname_name("/home/dieter/maxima/changelog.txt");
(%o2)                       changelog
(%i3) pathname_type("/home/dieter/maxima/changelog.txt");
(%o3)                          txt


Function: printfile (<path>)

     Prints the file named by <path> to the console.  <path> may be a
string or a symbol; if it is a symbol, it is converted to a string.

If <path> names a file which is accessible from the current working
directory, that file is printed to the console.  Otherwise,
printfile' attempts to locate the file by appending <path> to
each of the elements of file_search_usage' via filename_merge'.

printfile' returns <path> if it names an existing file, or
otherwise the result of a successful filename merge.


Function: save

          save (<filename>, <name_1>, <name_2>, <name_3>, ...)
save (<filename>, values, functions, labels, ...)
save (<filename>, [<m>, <n>])
save (<filename>, <name_1>=<expr_1>, ...)
save (<filename>, all)
save (<filename>, <name_1>=<expr_1>, <name_2>=<expr_2>, ...)
Stores the current values of <name_1>, <name_2>, <name_3>, ..., in
<filename>.  The arguments are the names of variables, functions,
or other objects.  If a name has no value or function associated
with it, it is ignored.  save' returns <filename>.

save' stores data in the form of Lisp expressions.  The data
stored by save' may be recovered by load (<filename>)'.  See

The global flag file_output_append' governs whether save'
appends or truncates the output file.  When file_output_append'
is true', save' appends to the output file.  Otherwise, save'
truncates the output file.  In either case, save' creates the
file if it does not yet exist.

The special form save (<filename>, values, functions, labels,
...)'  stores the items named by values', functions', labels',
etc.  The names may be any specified by the variable infolists'.
values' comprises all user-defined variables.

The special form save (<filename>, [<m>, <n>])' stores the values
of input and output labels <m> through <n>.  Note that <m> and <n>
must be literal integers.  Input and output labels may also be
stored one by one, e.g., save ("foo.1", %i42, %o42)'.  save
(<filename>, labels)' stores all input and output labels.  When
the stored labels are recovered, they clobber existing labels.

The special form save (<filename>, <name_1>=<expr_1>,
<name_2>=<expr_2>, ...)' stores the values of <expr_1>, <expr_2>,
..., with names <name_1>, <name_2>, ...  It is useful to apply
this form to input and output labels, e.g., save ("foo.1",
aa=%o88)'.  The right-hand side of the equality in this form may
be any expression, which is evaluated.  This form does not
introduce the new names into the current Maxima environment, but
only stores them in <filename>.

These special forms and the general form of save' may be mixed at
will.  For example, save (<filename>, aa, bb, cc=42, functions,
[11, 17])'.

The special form save (<filename>, all)' stores the current state
of Maxima.  This includes all user-defined variables, functions,
arrays, etc., as well as some automatically defined items.  The
saved items include system variables, such as file_search_maxima'
or showtime', if they have been assigned new values by the user;
see myoptions'.

save' evaluates <filename> and quotes all other arguments.


Function: stringout

          stringout (<filename>, <expr_1>, <expr_2>, <expr_3>, ...)
stringout (<filename>, [<m>, <n>])
stringout (<filename>, input)
stringout (<filename>, functions)
stringout (<filename>, values)
stringout' writes expressions to a file in the same form the
expressions would be typed for input.  The file can then be used
as input for the batch' or demo' commands, and it may be edited
for any purpose.  stringout' can be executed while writefile' is
in progress.

The global flag file_output_append' governs whether stringout'
appends or truncates the output file.  When file_output_append' is
true', stringout' appends to the output file.  Otherwise,
stringout' truncates the output file.  In either case, stringout'
creates the file if it does not yet exist.

The general form of stringout' writes the values of one or more
expressions to the output file.  Note that if an expression is a
variable, only the value of the variable is written and not the
name of the variable.  As a useful special case, the expressions
may be input labels (%i1', %i2', %i3', ...) or output labels
(%o1', %o2', %o3', ...).

If grind' is true', stringout' formats the output using the
grind' format.  Otherwise the string' format is used.  See
grind' and string'.

The special form stringout (<filename>, [<m>, <n>])' writes the
values of input labels m through n, inclusive.

The special form stringout (<filename>, input)' writes all input
labels to the file.

The special form stringout (<filename>, functions)' writes all
user-defined functions (named by the global list functions')) to
the file.

The special form stringout (<filename>, values)' writes all
user-assigned variables (named by the global list values')) to
the file.  Each variable is printed as an assignment statement,
with the name of the variable, a colon, and its value.  Note that
the general form of stringout' does not print variables as
assignment statements.


Function: with_stdout

          with_stdout (<f>, <expr_1>, <expr_2>, <expr_3>, ...)
with_stdout (<s>, <expr_1>, <expr_2>, <expr_3>, ...)
Evaluates <expr_1>, <expr_2>, <expr_3>, ... and writes any output
thus generated to a file <f> or output stream <s>.  The evaluated
expressions are not written to the output.  Output may be
generated by print', display', grind', among other functions.

The global flag file_output_append' governs whether with_stdout'
appends or truncates the output file <f>.  When
file_output_append' is true', with_stdout' appends to the
output file.  Otherwise, with_stdout' truncates the output file.
In either case, with_stdout' creates the file if it does not yet
exist.

with_stdout' returns the value of its final argument.

(%i1) with_stdout ("tmp.out", for i:5 thru 10 do
print (i, "! yields", i!))$(%i2) printfile ("tmp.out")$
5 ! yields 120
6 ! yields 720
7 ! yields 5040
8 ! yields 40320
9 ! yields 362880
10 ! yields 3628800


Function: writefile (<filename>)

     Begins writing a transcript of the Maxima session to <filename>.
All interaction between the user and Maxima is then recorded in
this file, just as it appears on the console.

As the transcript is printed in the console output format, it
cannot be reloaded into Maxima.  To make a file containing
expressions which can be reloaded, see save' and stringout'.
save' stores expressions in Lisp form, while stringout' stores
expressions in Maxima form.

The effect of executing writefile' when <filename> already exists
depends on the underlying Lisp implementation; the transcript file
may be clobbered, or the file may be appended.  appendfile'
always appends to the transcript file.

It may be convenient to execute playback' after writefile' to
save the display of previous interactions.  As playback' displays
only the input and output variables (%i1', %o1', etc.), any
output generated by a print statement in a function (as opposed to
a return value) is not displayed by playback'.

closefile' closes the transcript file opened by writefile' or
appendfile'.



## 13.4 Functions and Variables for TeX Output

Function: tex

          tex (<expr>)
tex (<expr>, <destination>)
tex (<expr>, false)
tex (<label>)
tex (<label>, <destination>)
tex (<label>, false)
Prints a representation of an expression suitable for the TeX
document preparation system.  The result is a fragment of a
document, which can be copied into a larger document but not
processed by itself.

tex (<expr>)' prints a TeX representation of <expr> on the
console.

tex (<label>)' prints a TeX representation of the expression
named by <label> and assigns it an equation label (to be displayed
to the left of the expression).  The TeX equation label is the
same as the Maxima label.

<destination> may be an output stream or file name.  When
<destination> is a file name, tex' appends its output to the
file.  The functions openw' and opena' create output streams.

tex (<expr>, false)' and tex (<label>, false)' return their TeX
output as a string.

tex' evaluates its first argument after testing it to see if it
is a label.  Quote-quote ''' forces evaluation of the argument,
thereby defeating the test and preventing the label.

See also texput'.

Examples:

(%i1) integrate (1/(1+x^3), x);
2 x - 1
2            atan(-------)
log(x  - x + 1)        sqrt(3)    log(x + 1)
(%o1)      - --------------- + ------------- + ----------
6             sqrt(3)          3
(%i2) tex (%o1);
$$-{{\log \left(x^2-x+1\right)}\over{6}}+{{\arctan \left({{2\,x-1 }\over{\sqrt{3}}}\right)}\over{\sqrt{3}}}+{{\log \left(x+1\right) }\over{3}}\leqno{\tt (\%o1)}$$
(%o2)                          (\%o1)
(%i3) tex (integrate (sin(x), x));
$$-\cos x$$
(%o3)                           false
(%i4) tex (%o1, "foo.tex");
(%o4)                          (\%o1)

tex (<expr>, false)' returns its TeX output as a string.

(%i1) S : tex (x * y * z, false);
(%o1) $$x\,y\,z$$
(%i2) S;
(%o2) $$x\,y\,z$$


Function: tex1 (<e>)

     Returns a string which represents the TeX output for the
expressions <e>.  The TeX output is not enclosed in delimiters for
an equation or any other environment.

Examples:

(%i1) tex1 (sin(x) + cos(x));
(%o1)                     \sin x+\cos x


Function: texput

          texput (<a>, <s>)
texput (<a>, <f>)
texput (<a>, <s>, <operator_type>)
texput (<a>, [<s_1>, <s_2>], matchfix)
texput (<a>, [<s_1>, <s_2>, <s_3>], matchfix)
Assign the TeX output for the atom <a>, which can be a symbol or
the name of an operator.

texput (<a>, <s>)' causes the tex' function to interpolate the
string <s> into the TeX output in place of <a>.

texput (<a>, <f>)' causes the tex' function to call the function
<f> to generate TeX output.  <f> must accept one argument, which
is an expression which has operator <a>, and must return a string
(the TeX output).  <f> may call tex1' to generate TeX output for
the arguments of the input expression.

texput (<a>, <s>, <operator_type>)', where <operator_type> is
prefix', infix', postfix', nary', or nofix', causes the tex'
function to interpolate <s> into the TeX output in place of <a>,
and to place the interpolated text in the appropriate position.

texput (<a>, [<s_1>, <s_2>], matchfix)' causes the tex' function
to interpolate <s_1> and <s_2> into the TeX output on either side
of the arguments of <a>.  The arguments (if more than one) are
separated by commas.

texput (<a>, [<s_1>, <s_2>, <s_3>], matchfix)' causes the tex'
function to interpolate <s_1> and <s_2> into the TeX output on
either side of the arguments of <a>, with <s_3> separating the
arguments.

Examples:

Assign TeX output for a variable.

(%i1) texput (me,"\\mu_e");
(%o1)                         \mu_e
(%i2) tex (me);
$$\mu_e$$
(%o2)                         false

Assign TeX output for an ordinary function (not an operator).

(%i1) texput (lcm, "\\mathrm{lcm}");
(%o1)                     \mathrm{lcm}
(%i2) tex (lcm (a, b));
$$\mathrm{lcm}\left(a , b\right)$$
(%o2)                         false

Call a function to generate TeX output.

(%i1) texfoo (e) := block ([a, b], [a, b] : args (e),
concat("\\left[\\stackrel{",tex1(b),"}{",tex1(a),"}\\right]"))$(%i2) texput (foo, texfoo); (%o2) texfoo (%i3) tex (foo (2^x, %pi)); $$\left[\stackrel{\pi}{2^{x}}\right]$$ (%o3) false Assign TeX output for a prefix operator. (%i1) prefix ("grad"); (%o1) grad (%i2) texput ("grad", " \\nabla ", prefix); (%o2) \nabla (%i3) tex (grad f); $$\nabla f$$ (%o3) false Assign TeX output for an infix operator. (%i1) infix ("~"); (%o1) ~ (%i2) texput ("~", " \\times ", infix); (%o2) \times (%i3) tex (a ~ b); $$a \times b$$ (%o3) false Assign TeX output for a postfix operator. (%i1) postfix ("##"); (%o1) ## (%i2) texput ("##", "!!", postfix); (%o2) !! (%i3) tex (x ##); $$x!!$$ (%o3) false Assign TeX output for a nary operator. (%i1) nary ("@@"); (%o1) @@ (%i2) texput ("@@", " \\circ ", nary); (%o2) \circ (%i3) tex (a @@ b @@ c @@ d); $$a \circ b \circ c \circ d$$ (%o3) false Assign TeX output for a nofix operator. (%i1) nofix ("foo"); (%o1) foo (%i2) texput ("foo", "\\mathsc{foo}", nofix); (%o2) \mathsc{foo} (%i3) tex (foo); $$\mathsc{foo}$$ (%o3) false Assign TeX output for a matchfix operator. (%i1) matchfix ("<<", ">>"); (%o1) << (%i2) texput ("<<", [" \\langle ", " \\rangle "], matchfix); (%o2) [ \langle , \rangle ] (%i3) tex (<<a>>); $$\langle a \rangle$$ (%o3) false (%i4) tex (<<a, b>>); $$\langle a , b \rangle$$ (%o4) false (%i5) texput ("<<", [" \\langle ", " \\rangle ", " \\, | \\,"], matchfix); (%o5) [ \langle , \rangle , \, | \,] (%i6) tex (<<a>>); $$\langle a \rangle$$ (%o6) false (%i7) tex (<<a, b>>); $$\langle a \, | \,b \rangle$$ (%o7) false  Function: get_tex_environment (<op>)  Function: set_tex_environment (<op>, <before>, <after>)   Customize the TeX environment output by tex'. As maintained by these functions, the TeX environment comprises two strings: one is printed before any other TeX output, and the other is printed after. Only the TeX environment of the top-level operator in an expression is output; TeX environments associated with other operators are ignored. get_tex_environment' returns the TeX enviroment which is applied to the operator <op>; returns the default if no other environment has been assigned. set_tex_environment' assigns the TeX environment for the operator <op>. Examples: (%i1) get_tex_environment (":="); (%o1) [ \begin{verbatim} , ; \end{verbatim} ] (%i2) tex (f (x) := 1 - x); \begin{verbatim} f(x):=1-x; \end{verbatim} (%o2) false (%i3) set_tex_environment (":=", "$$", "$$"); (%o3) [$$,$$] (%i4) tex (f (x) := 1 - x); $$f(x):=1-x$$ (%o4) false  Function: get_tex_environment_default ()  Function: set_tex_environment_default (<before>, <after>)   Customize the TeX environment output by tex'. As maintained by these functions, the TeX environment comprises two strings: one is printed before any other TeX output, and the other is printed after. get_tex_environment_default' returns the TeX environment which is applied to expressions for which the top-level operator has no specific TeX environment (as assigned by set_tex_environment'). set_tex_environment_default' assigns the default TeX environment. Examples: (%i1) get_tex_environment_default (); (%o1) [$$,$$] (%i2) tex (f(x) + g(x)); $$g\left(x\right)+f\left(x\right)$$ (%o2) false (%i3) set_tex_environment_default ("\\begin{equation} ", " \\end{equation}"); (%o3) [\begin{equation} , \end{equation}] (%i4) tex (f(x) + g(x)); \begin{equation} g\left(x\right)+f\left(x\right) \end{equation} (%o4) false  ## 13.5 Functions and Variables for Fortran Output Option variable: fortindent   Default value: 0' fortindent' controls the left margin indentation of expressions printed out by the fortran' command. 0' gives normal printout (i.e., 6 spaces), and positive values will causes the expressions to be printed farther to the right.  Function: fortran (<expr>)   Prints <expr> as a Fortran statement. The output line is indented with spaces. If the line is too long, fortran' prints continuation lines. fortran' prints the exponentiation operator ^' as **', and prints a complex number a + b %i' in the form (a,b)'. <expr> may be an equation. If so, fortran' prints an assignment statement, assigning the right-hand side of the equation to the left-hand side. In particular, if the right-hand side of <expr> is the name of a matrix, then fortran' prints an assignment statement for each element of the matrix. If <expr> is not something recognized by fortran', the expression is printed in grind' format without complaint. fortran' does not know about lists, arrays, or functions. fortindent' controls the left margin of the printed lines. 0' is the normal margin (i.e., indented 6 spaces). Increasing fortindent' causes expressions to be printed further to the right. When fortspaces' is true', fortran' fills out each printed line with spaces to 80 columns. fortran' evaluates its arguments; quoting an argument defeats evaluation. fortran' always returns done'. See also the function f90' for printing one or more expressions as a Fortran 90 program. Examples: (%i1) expr: (a + b)^12$
(%i2) fortran (expr);
(b+a)**12
(%o2)                         done
(%i3) fortran ('x=expr);
x = (b+a)**12
(%o3)                         done
(%i4) fortran ('x=expand (expr));
x = b**12+12*a*b**11+66*a**2*b**10+220*a**3*b**9+495*a**4*b**8+792
1   *a**5*b**7+924*a**6*b**6+792*a**7*b**5+495*a**8*b**4+220*a**9*b
2   **3+66*a**10*b**2+12*a**11*b+a**12
(%o4)                         done
(%i5) fortran ('x=7+5*%i);
x = (7,5)
(%o5)                         done
(%i6) fortran ('x=[1,2,3,4]);
x = [1,2,3,4]
(%o6)                         done
(%i7) f(x) := x^2$(%i8) fortran (f); f (%o8) done  Option variable: fortspaces   Default value: false' When fortspaces' is true', fortran' fills out each printed line with spaces to 80 columns.  ## 14 Polynomials  Introduction to Polynomials Functions and Variables for Polynomials  ## 14.1 Introduction to Polynomials Polynomials are stored in Maxima either in General Form or as Canonical Rational Expressions (CRE) form. The latter is a standard form, and is used internally by operations such as factor, ratsimp, and so on. Canonical Rational Expressions constitute a kind of representation which is especially suitable for expanded polynomials and rational functions (as well as for partially factored polynomials and rational functions when RATFAC is set to true'). In this CRE form an ordering of variables (from most to least main) is assumed for each expression. Polynomials are represented recursively by a list consisting of the main variable followed by a series of pairs of expressions, one for each term of the polynomial. The first member of each pair is the exponent of the main variable in that term and the second member is the coefficient of that term which could be a number or a polynomial in another variable again represented in this form. Thus the principal part of the CRE form of 3*X^2-1 is (X 2 3 0 -1) and that of 2*X*Y+X-3 is (Y 1 (X 1 2) 0 (X 1 1 0 -3)) assuming Y is the main variable, and is (X 1 (Y 1 2 0 1) 0 -3) assuming X is the main variable. "Main"-ness is usually determined by reverse alphabetical order. The "variables" of a CRE expression needn't be atomic. In fact any subexpression whose main operator is not + - * / or ^ with integer power will be considered a "variable" of the expression (in CRE form) in which it occurs. For example the CRE variables of the expression X+SIN(X+1)+2*SQRT(X)+1 are X, SQRT(X), and SIN(X+1). If the user does not specify an ordering of variables by using the RATVARS function Maxima will choose an alphabetic one. In general, CRE's represent rational expressions, that is, ratios of polynomials, where the numerator and denominator have no common factors, and the denominator is positive. The internal form is essentially a pair of polynomials (the numerator and denominator) preceded by the variable ordering list. If an expression to be displayed is in CRE form or if it contains any subexpressions in CRE form, the symbol /R/ will follow the line label. See the RAT function for converting an expression to CRE form. An extended CRE form is used for the representation of Taylor series. The notion of a rational expression is extended so that the exponents of the variables can be positive or negative rational numbers rather than just positive integers and the coefficients can themselves be rational expressions as described above rather than just polynomials. These are represented internally by a recursive polynomial form which is similar to and is a generalization of CRE form, but carries additional information such as the degree of truncation. As with CRE form, the symbol /T/ follows the line label of such expressions.  ## 14.2 Functions and Variables for Polynomials Option variable: algebraic   Default value: false' algebraic' must be set to true' in order for the simplification of algebraic integers to take effect.  Option variable: berlefact   Default value: true' When berlefact' is false' then the Kronecker factoring algorithm will be used otherwise the Berlekamp algorithm, which is the default, will be used.  Function: bezout (<p1>, <p2>, <x>)   an alternative to the resultant' command. It returns a matrix. determinant' of this matrix is the desired resultant. Examples: (%i1) bezout(a*x+b, c*x^2+d, x); [ b c - a d ] (%o1) [ ] [ a b ] (%i2) determinant(%); 2 2 (%o2) a d + b c (%i3) resultant(a*x+b, c*x^2+d, x); 2 2 (%o3) a d + b c  Function: bothcoef (<expr>, <x>)   Returns a list whose first member is the coefficient of <x> in <expr> (as found by ratcoef' if <expr> is in CRE form otherwise by coeff') and whose second member is the remaining part of <expr>. That is, [A, B]' where <expr> = A*<x> + B'. Example: (%i1) islinear (expr, x) := block ([c], c: bothcoef (rat (expr, x), x), is (freeof (x, c) and c # 0))$
(%i2) islinear ((r^2 - (x - r)^2)/x, x);
(%o2)                         true


Function: coeff

          coeff (<expr>, <x>, <n>)
coeff (<expr>, <x>)
Returns the coefficient of <x>^<n>' in <expr>, where <expr> is a
polynomial or a monomial term in <x>.

coeff(<expr>, <x>^<n>)' is equivalent to coeff(<expr>, <x>,
<n>)'.  coeff(<expr>, <x>, 0)' returns the remainder of <expr>
which is free of <x>.  If omitted, <n> is assumed to be 1.

<x> may be a simple variable or a subscripted variable, or a
subexpression of <expr> which comprises an operator and all of its
arguments.

It may be possible to compute coefficients of expressions which
are equivalent to <expr> by applying expand' or factor'.
coeff' itself does not apply expand' or factor' or any other
function.

coeff' distributes over lists, matrices, and equations.

Examples:

coeff' returns the coefficient <x>^<n>' in <expr>.

(%i1) coeff (b^3*a^3 + b^2*a^2 + b*a + 1, a^3);
3
(%o1)                          b

coeff(<expr>, <x>^<n>)' is equivalent to coeff(<expr>, <x>,
<n>)'.

(%i1) coeff (c*z^4 - c*z^3 - c*z^2 + c*z, z, 3);
(%o1)                         - c
3
(%i2) coeff (c*z^4 - c*z^3 - c*z^2 + c*z, z^3);
(%o2)                         - c
3

coeff(<expr>, <x>, 0)' returns the remainder of <expr> which is
free of <x>.

(%i1) coeff (a*u + b^2*u^2 + c^3*u^3, b, 0);
3  3
(%o1)                      c  u  + a u

<x> may be a simple variable or a subscripted variable, or a
subexpression of <expr> which comprises an operator and all of its
arguments.

(%i1) coeff (h^4 - 2*%pi*h^2 + 1, h, 2);
(%o1)                        - 2 %pi
(%i2) coeff (v^4 - 2*%pi*v^2 + 1, v, 2);
(%o2)                        - 2 %pi
(%i3) coeff (sin(1+x)*sin(x) + sin(1+x)^3*sin(x)^3, sin(1+x)^3);
3
(%o3)                        sin (x)
(%i4) coeff ((d - a)^2*(b + c)^3 + (a + b)^4*(c - d), a + b, 4);
(%o4)                         c - d

coeff' itself does not apply expand' or factor' or any other
function.

(%i1) coeff (c*(a + b)^3, a);
(%o1)                           0
(%i2) expand (c*(a + b)^3);
3          2        2        3
(%o2)           b  c + 3 a b  c + 3 a  b c + a  c
(%i3) coeff (%, a);
2
(%o3)                        3 b  c
(%i4) coeff (b^3*c + 3*a*b^2*c + 3*a^2*b*c + a^3*c, (a + b)^3);
(%o4)                           0
(%i5) factor (b^3*c + 3*a*b^2*c + 3*a^2*b*c + a^3*c);
3
(%o5)                      (b + a)  c
(%i6) coeff (%, (a + b)^3);
(%o6)                           c

coeff' distributes over lists, matrices, and equations.

(%i1) coeff ([4*a, -3*a, 2*a], a);
(%o1)                      [4, - 3, 2]
(%i2) coeff (matrix ([a*x, b*x], [-c*x, -d*x]), x);
[  a    b  ]
(%o2)                     [          ]
[ - c  - d ]
(%i3) coeff (a*u - b*v = 7*u + 3*v, u);
(%o3)                         a = 7


Function: content (<p_1>, <x_1>, ..., <x_n>)

     Returns a list whose first element is the greatest common divisor
of the coefficients of the terms of the polynomial <p_1> in the
variable <x_n> (this is the content) and whose second element is
the polynomial <p_1> divided by the content.

Examples:

(%i1) content (2*x*y + 4*x^2*y^2, y);
2
(%o1)                   [2 x, 2 x y  + y]


Function: denom (<expr>)

     Returns the denominator of the rational expression <expr>.


Function: divide (<p_1>, <p_2>, <x_1>, ..., <x_n>)

     computes the quotient and remainder of the polynomial <p_1>
divided by the polynomial <p_2>, in a main polynomial variable,
<x_n>.  The other variables are as in the ratvars' function.  The
result is a list whose first element is the quotient and whose
second element is the remainder.

Examples:

(%i1) divide (x + y, x - y, x);
(%o1)                       [1, 2 y]
(%i2) divide (x + y, x - y);
(%o2)                      [- 1, 2 x]

Note that y' is the main variable in the second example.


Function: eliminate ([<eqn_1>, ..., <eqn_n>], [<x_1>, ..., <x_k>])

     Eliminates variables from equations (or expressions assumed equal
to zero) by taking successive resultants. This returns a list of
<n> - <k>' expressions with the <k> variables <x_1>, ..., <x_k>
eliminated.  First <x_1> is eliminated yielding <n> - 1'
expressions, then x_2' is eliminated, etc.  If <k> = <n>' then a
single expression in a list is returned free of the variables
<x_1>, ..., <x_k>.  In this case solve' is called to solve the
last resultant for the last variable.

Example:

(%i1) expr1: 2*x^2 + y*x + z;
2
(%o1)                    z + x y + 2 x
(%i2) expr2: 3*x + 5*y - z - 1;
(%o2)                  - z + 5 y + 3 x - 1
(%i3) expr3: z^2 + x - y^2 + 5;
2    2
(%o3)                    z  - y  + x + 5
(%i4) eliminate ([expr3, expr2, expr1], [y, z]);
8         7         6          5          4
(%o4) [7425 x  - 1170 x  + 1299 x  + 12076 x  + 22887 x

3         2
- 5154 x  - 1291 x  + 7688 x + 15376]


Function: ezgcd (<p_1>, <p_2>, <p_3>, ...)

     Returns a list whose first element is the greatest common divisor
of the polynomials <p_1>, <p_2>, <p_3>, ... and whose remaining
elements are the polynomials divided by the greatest common
divisor.  This always uses the ezgcd' algorithm.

See also gcd', gcdex', gcdivide', and poly_gcd'.

Examples:

The three polynomials have the greatest common divisor 2*x-3'.
The gcd is first calculated with the function gcd' and then with
the function ezgcd'.

(%i1) p1 : 6*x^3-17*x^2+14*x-3;
3       2
(%o1)                6 x  - 17 x  + 14 x - 3
(%i2) p2 : 4*x^4-14*x^3+12*x^2+2*x-3;
4       3       2
(%o2)            4 x  - 14 x  + 12 x  + 2 x - 3
(%i3) p3 : -8*x^3+14*x^2-x-3;
3       2
(%o3)                - 8 x  + 14 x  - x - 3

(%i4) gcd(p1, gcd(p2, p3));
(%o4)                        2 x - 3

(%i5) ezgcd(p1, p2, p3);
2               3      2           2
(%o5) [2 x - 3, 3 x  - 4 x + 1, 2 x  - 4 x  + 1, - 4 x  + x + 1]


Option variable: facexpand

     Default value: true'

facexpand' controls whether the irreducible factors returned by
factor' are in expanded (the default) or recursive (normal CRE)
form.


Function: factor

          factor (<expr>)
factor (<expr>, <p>)
Factors the expression <expr>, containing any number of variables
or functions, into factors irreducible over the integers.  factor
(<expr>, <p>)' factors <expr> over the field of rationals with an
element adjoined whose minimum polynomial is <p>.

factor' uses ifactors' function for factoring integers.

factorflag' if false' suppresses the factoring of integer factors
of rational expressions.

dontfactor' may be set to a list of variables with respect to
which factoring is not to occur.  (It is initially empty).
Factoring also will not take place with respect to any variables
which are less important (using the variable ordering assumed for
CRE form) than those on the dontfactor' list.

savefactors' if true' causes the factors of an expression which
is a product of factors to be saved by certain functions in order
to speed up later factorizations of expressions containing some of
the same factors.

berlefact' if false' then the Kronecker factoring algorithm will
be used otherwise the Berlekamp algorithm, which is the default,
will be used.

intfaclim' if true' maxima will give up factorization of
integers if no factor is found after trial divisions and Pollard's
rho method.  If set to false' (this is the case when the user
calls factor' explicitly), complete factorization of the integer
will be attempted.  The user's setting of intfaclim' is used for
internal calls to factor'.  Thus, intfaclim' may be reset to
prevent Maxima from taking an inordinately long time factoring
large integers.

Examples:

(%i1) factor (2^63 - 1);
2
(%o1)              7  73 127 337 92737 649657
(%i2) factor (-8*y - 4*x + z^2*(2*y + x));
(%o2)               (2 y + x) (z - 2) (z + 2)
(%i3) -1 - 2*x - x^2 + y^2 + 2*x*y^2 + x^2*y^2;
2  2        2    2    2
(%o3)          x  y  + 2 x y  + y  - x  - 2 x - 1
(%i4) block ([dontfactor: [x]], factor (%/36/(1 + 2*y + y^2)));
2
(x  + 2 x + 1) (y - 1)
(%o4)                ----------------------
36 (y + 1)
(%i5) factor (1 + %e^(3*x));
x         2 x     x
(%o5)              (%e  + 1) (%e    - %e  + 1)
(%i6) factor (1 + x^4, a^2 - 2);
2              2
(%o6)             (x  - a x + 1) (x  + a x + 1)
(%i7) factor (-y^2*z^2 - x*z^2 + x^2*y^2 + x^3);
2
(%o7)              - (y  + x) (z - x) (z + x)
(%i8) (2 + x)/(3 + x)/(b + x)/(c + x)^2;
x + 2
(%o8)               ------------------------
2
(x + 3) (x + b) (x + c)
(%i9) ratsimp (%);
4                  3
(%o9) (x + 2)/(x  + (2 c + b + 3) x

2                       2             2                   2
+ (c  + (2 b + 6) c + 3 b) x  + ((b + 3) c  + 6 b c) x + 3 b c )
(%i10) partfrac (%, x);
2                   4                3
(%o10) - (c  - 4 c - b + 6)/((c  + (- 2 b - 6) c

2              2         2                2
+ (b  + 12 b + 9) c  + (- 6 b  - 18 b) c + 9 b ) (x + c))

c - 2
- ---------------------------------
2                             2
(c  + (- b - 3) c + 3 b) (x + c)

b - 2
+ -------------------------------------------------
2             2       3      2
((b - 3) c  + (6 b - 2 b ) c + b  - 3 b ) (x + b)

1
- ----------------------------------------------
2
((b - 3) c  + (18 - 6 b) c + 9 b - 27) (x + 3)
(%i11) map ('factor, %);
2
c  - 4 c - b + 6                 c - 2
(%o11) - ------------------------- - ------------------------
2        2                                  2
(c - 3)  (c - b)  (x + c)   (c - 3) (c - b) (x + c)

b - 2                        1
+ ------------------------ - ------------------------
2                          2
(b - 3) (c - b)  (x + b)   (b - 3) (c - 3)  (x + 3)
(%i12) ratsimp ((x^5 - 1)/(x - 1));
4    3    2
(%o12)                x  + x  + x  + x + 1
(%i13) subst (a, x, %);
4    3    2
(%o13)                a  + a  + a  + a + 1
(%i14) factor (%th(2), %);
2        3        3    2
(%o14)   (x - a) (x - a ) (x - a ) (x + a  + a  + a + 1)
(%i15) factor (1 + x^12);
4        8    4
(%o15)               (x  + 1) (x  - x  + 1)
(%i16) factor (1 + x^99);
2            6    3
(%o16) (x + 1) (x  - x + 1) (x  - x  + 1)

10    9    8    7    6    5    4    3    2
(x   - x  + x  - x  + x  - x  + x  - x  + x  - x + 1)

20    19    17    16    14    13    11    10    9    7    6
(x   + x   - x   - x   + x   + x   - x   - x   - x  + x  + x

4    3            60    57    51    48    42    39    33
- x  - x  + x + 1) (x   + x   - x   - x   + x   + x   - x

30    27    21    18    12    9    3
- x   - x   + x   + x   - x   - x  + x  + 1)


Option variable: factorflag

     Default value: false'

When factorflag' is false', suppresses the factoring of integer
factors of rational expressions.


Function: factorout (<expr>, <x_1>, <x_2>, ...)

     Rearranges the sum <expr> into a sum of terms of the form f
(<x_1>, <x_2>, ...)*g' where g' is a product of expressions not
containing any <x_i> and f' is factored.

Note that the option variable keepfloat' is ignored by
factorout'.

Example:

(%i1) expand (a*(x+1)*(x-1)*(u+1)^2);
2  2          2      2      2
(%o1)     a u  x  + 2 a u x  + a x  - a u  - 2 a u - a
(%i2) factorout(%,x);
2
(%o2) a u  (x - 1) (x + 1) + 2 a u (x - 1) (x + 1)
+ a (x - 1) (x + 1)


Function: factorsum (<expr>)

     Tries to group terms in factors of <expr> which are sums into
groups of terms such that their sum is factorable.  factorsum'
can recover the result of expand ((x + y)^2 + (z + w)^2)' but it
can't recover expand ((x + 1)^2 + (x + y)^2)' because the terms
have variables in common.

Example:

(%i1) expand ((x + 1)*((u + v)^2 + a*(w + z)^2));
2      2                            2      2
(%o1) a x z  + a z  + 2 a w x z + 2 a w z + a w  x + v  x

2        2    2            2
+ 2 u v x + u  x + a w  + v  + 2 u v + u
(%i2) factorsum (%);
2          2
(%o2)            (x + 1) (a (z + w)  + (v + u) )


Function: fasttimes (<p_1>, <p_2>)

     Returns the product of the polynomials <p_1> and <p_2> by using a
special algorithm for multiplication of polynomials.  p_1' and
p_2' should be multivariate, dense, and nearly the same size.
Classical multiplication is of order n_1 n_2' where n_1' is the
degree of p_1' and n_2' is the degree of p_2'.  fasttimes' is
of order max (n_1, n_2)^1.585'.


Function: fullratsimp (<expr>)

     fullratsimp' repeatedly applies ratsimp' followed by
non-rational simplification to an expression until no further
change occurs, and returns the result.

When non-rational expressions are involved, one call to ratsimp'
followed as is usual by non-rational ("general") simplification
may not be sufficient to return a simplified result.  Sometimes,
more than one such call may be necessary.  fullratsimp' makes
this process convenient.

fullratsimp (<expr>, <x_1>, ..., <x_n>)' takes one or more
arguments similar to ratsimp' and rat'.

Example:

(%i1) expr: (x^(a/2) + 1)^2*(x^(a/2) - 1)^2/(x^a - 1);
a/2     2   a/2     2
(x    - 1)  (x    + 1)
(%o1)                -----------------------
a
x  - 1
(%i2) ratsimp (expr);
2 a      a
x    - 2 x  + 1
(%o2)                    ---------------
a
x  - 1
(%i3) fullratsimp (expr);
a
(%o3)                        x  - 1
(%i4) rat (expr);
a/2 4       a/2 2
(x   )  - 2 (x   )  + 1
(%o4)/R/             -----------------------
a
x  - 1


Function: fullratsubst (<a>, <b>, <c>)

     is the same as ratsubst' except that it calls itself recursively
on its result until that result stops changing.  This function is
useful when the replacement expression and the replaced expression
have one or more variables in common.

fullratsubst' will also accept its arguments in the format of
lratsubst'.  That is, the first argument may be a single
substitution equation or a list of such equations, while the
second argument is the expression being processed.

load ("lrats")' loads fullratsubst' and lratsubst'.

Examples:

(%i1) load ("lrats")$* subst' can carry out multiple substitutions. lratsubst' is analogous to subst'. (%i2) subst ([a = b, c = d], a + c); (%o2) d + b (%i3) lratsubst ([a^2 = b, c^2 = d], (a + e)*c*(a + c)); (%o3) (d + a c) e + a d + b c * If only one substitution is desired, then a single equation may be given as first argument. (%i4) lratsubst (a^2 = b, a^3); (%o4) a b * fullratsubst' is equivalent to ratsubst' except that it recurses until its result stops changing. (%i5) ratsubst (b*a, a^2, a^3); 2 (%o5) a b (%i6) fullratsubst (b*a, a^2, a^3); 2 (%o6) a b * fullratsubst' also accepts a list of equations or a single equation as first argument. (%i7) fullratsubst ([a^2 = b, b^2 = c, c^2 = a], a^3*b*c); (%o7) b (%i8) fullratsubst (a^2 = b*a, a^3); 2 (%o8) a b * fullratsubst' may cause an indefinite recursion. (%i9) errcatch (fullratsubst (b*a^2, a^2, a^3)); *** - Lisp stack overflow. RESET  Function: gcd (<p_1>, <p_2>, <x_1>, ...)   Returns the greatest common divisor of <p_1> and <p_2>. The flag gcd' determines which algorithm is employed. Setting gcd' to ez', subres', red', or spmod' selects the ezgcd', subresultant prs', reduced, or modular algorithm, respectively. If gcd' false' then gcd (<p_1>, <p_2>, <x>)' always returns 1 for all <x>. Many functions (e.g. ratsimp', factor', etc.) cause gcd's to be taken implicitly. For homogeneous polynomials it is recommended that gcd' equal to subres' be used. To take the gcd when an algebraic is present, e.g., gcd (<x>^2 - 2*sqrt(2)* <x> + 2, <x> - sqrt(2))', the option variable algebraic' must be true' and gcd' must not be ez'. The gcd' flag, default: spmod', if false' will also prevent the greatest common divisor from being taken when expressions are converted to canonical rational expression (CRE) form. This will sometimes speed the calculation if gcds are not required. See also ezgcd', gcdex', gcdivide', and poly_gcd'. Example: (%i1) p1:6*x^3+19*x^2+19*x+6; 3 2 (%o1) 6 x + 19 x + 19 x + 6 (%i2) p2:6*x^5+13*x^4+12*x^3+13*x^2+6*x; 5 4 3 2 (%o2) 6 x + 13 x + 12 x + 13 x + 6 x (%i3) gcd(p1, p2); 2 (%o3) 6 x + 13 x + 6 (%i4) p1/gcd(p1, p2), ratsimp; (%o4) x + 1 (%i5) p2/gcd(p1, p2), ratsimp; 3 (%o5) x + x ezgcd' returns a list whose first element is the greatest common divisor of the polynomials <p_1> and <p_2>, and whose remaining elements are the polynomials divided by the greatest common divisor. (%i6) ezgcd(p1, p2); 2 3 (%o6) [6 x + 13 x + 6, x + 1, x + x]  Function: gcdex   gcdex (<f>, <g>) gcdex (<f>, <g>, <x>) Returns a list [<a>, <b>, <u>]' where <u> is the greatest common divisor (gcd) of <f> and <g>, and <u> is equal to <a> <f> + <b> <g>'. The arguments <f> and <g> should be univariate polynomials, or else polynomials in <x> a supplied main variable since we need to be in a principal ideal domain for this to work. The gcd means the gcd regarding <f> and <g> as univariate polynomials with coefficients being rational functions in the other variables. gcdex' implements the Euclidean algorithm, where we have a sequence of L[i]: [a[i], b[i], r[i]]' which are all perpendicular to [f, g, -1]' and the next one is built as if q = quotient(r[i]/r[i+1])' then L[i+2]: L[i] - q L[i+1]', and it terminates at L[i+1]' when the remainder r[i+2]' is zero. The arguments <f> and <g> can be integers. For this case the function igcdex' is called by gcdex'. See also ezgcd', gcd', gcdivide', and poly_gcd'. Examples: (%i1) gcdex (x^2 + 1, x^3 + 4); 2 x + 4 x - 1 x + 4 (%o1)/R/ [- ------------, -----, 1] 17 17 (%i2) % . [x^2 + 1, x^3 + 4, -1]; (%o2)/R/ 0 Note that the gcd in the following is 1' since we work in k(y)[x]', not the y+1' we would expect in k[y, x]'. (%i1) gcdex (x*(y + 1), y^2 - 1, x); 1 (%o1)/R/ [0, ------, 1] 2 y - 1  Function: gcfactor (<n>)   Factors the Gaussian integer <n> over the Gaussian integers, i.e., numbers of the form <a> + <b> %i'' where <a> and <b> are rational integers (i.e., ordinary integers). Factors are normalized by making <a> and <b> non-negative.  Function: gfactor (<expr>)   Factors the polynomial <expr> over the Gaussian integers (that is, the integers with the imaginary unit %i' adjoined). This is like factor (<expr>, <a>^2+1)' where <a> is %i'. Example: (%i1) gfactor (x^4 - 1); (%o1) (x - 1) (x + 1) (x - %i) (x + %i)  Function: gfactorsum (<expr>)   is similar to factorsum' but applies gfactor' instead of factor'.  Function: hipow (<expr>, <x>)   Returns the highest explicit exponent of <x> in <expr>. <x> may be a variable or a general expression. If <x> does not appear in <expr>, hipow' returns 0'. hipow' does not consider expressions equivalent to expr'. In particular, hipow' does not expand expr', so hipow (<expr>, <x>)' and hipow (expand (<expr>, <x>))' may yield different results. Examples: (%i1) hipow (y^3 * x^2 + x * y^4, x); (%o1) 2 (%i2) hipow ((x + y)^5, x); (%o2) 1 (%i3) hipow (expand ((x + y)^5), x); (%o3) 5 (%i4) hipow ((x + y)^5, x + y); (%o4) 5 (%i5) hipow (expand ((x + y)^5), x + y); (%o5) 0  Option variable: intfaclim   Default value: true If true', maxima will give up factorization of integers if no factor is found after trial divisions and Pollard's rho method and factorization will not be complete. When intfaclim' is false' (this is the case when the user calls factor' explicitly), complete factorization will be attempted. intfaclim' is set to false' when factors are computed in divisors', divsum' and totient'. Internal calls to factor' respect the user-specified value of intfaclim'. Setting intfaclim' to true' may reduce the time spent factoring large integers.  Option variable: keepfloat   Default value: false' When keepfloat' is true', prevents floating point numbers from being rationalized when expressions which contain them are converted to canonical rational expression (CRE) form. Note that the function solve' and those functions calling it (eigenvalues', for example) currently ignore this flag, converting floating point numbers anyway. Examples: (%i1) rat(x/2.0); rat' replaced 0.5 by 1/2 = 0.5 x (%o1)/R/ - 2 (%i2) rat(x/2.0), keepfloat; (%o2)/R/ 0.5 x solve' ignores keepfloat': (%i3) solve(1.0-x,x), keepfloat; rat' replaced 1.0 by 1/1 = 1.0 (%o3) [x = 1]  Function: lopow (<expr>, <x>)   Returns the lowest exponent of <x> which explicitly appears in <expr>. Thus (%i1) lopow ((x+y)^2 + (x+y)^a, x+y); (%o1) min(a, 2)  Function: lratsubst (<L>, <expr>)   is analogous to subst (<L>, <expr>)' except that it uses ratsubst' instead of subst'. The first argument of lratsubst' is an equation or a list of equations identical in format to that accepted by subst'. The substitutions are made in the order given by the list of equations, that is, from left to right. load ("lrats")' loads fullratsubst' and lratsubst'. Examples: (%i1) load ("lrats")$

* subst' can carry out multiple substitutions.  lratsubst' is
analogous to subst'.

(%i2) subst ([a = b, c = d], a + c);
(%o2)                         d + b
(%i3) lratsubst ([a^2 = b, c^2 = d], (a + e)*c*(a + c));
(%o3)                (d + a c) e + a d + b c

* If only one substitution is desired, then a single equation
may be given as first argument.

(%i4) lratsubst (a^2 = b, a^3);
(%o4)                          a b


Option variable: modulus

     Default value: false'

When modulus' is a positive number <p>, operations on rational
numbers (as returned by rat' and related functions) are carried
out modulo <p>, using the so-called "balanced" modulus system in
which <n> modulo <p>' is defined as an integer <k> in
[-(<p>-1)/2, ..., 0, ..., (<p>-1)/2]' when <p> is odd, or
[-(<p>/2 - 1), ..., 0, ...., <p>/2]' when <p> is even, such that
<a> <p> + <k>' equals <n> for some integer <a>.

If <expr> is already in canonical rational expression (CRE) form
when modulus' is reset, then you may need to re-rat <expr>, e.g.,
expr: rat (ratdisrep (expr))', in order to get correct results.

Typically modulus' is set to a prime number.  If modulus' is set
to a positive non-prime integer, this setting is accepted, but a
warning message is displayed.  Maxima signals an error, when zero
or a negative integer is assigned to modulus'.

Examples:

(%i1) modulus:7;
(%o1)                           7
(%i2) polymod([0,1,2,3,4,5,6,7]);
(%o2)            [0, 1, 2, 3, - 3, - 2, - 1, 0]
(%i3) modulus:false;
(%o3)                         false
(%i4) poly:x^6+x^2+1;
6    2
(%o4)                      x  + x  + 1
(%i5) factor(poly);
6    2
(%o5)                      x  + x  + 1
(%i6) modulus:13;
(%o6)                          13
(%i7) factor(poly);
2        4      2
(%o7)               (x  + 6) (x  - 6 x  - 2)
(%i8) polymod(%);
6    2
(%o8)                      x  + x  + 1


Function: num (<expr>)

     Returns the numerator of <expr> if it is a ratio.  If <expr> is
not a ratio, <expr> is returned.

num' evaluates its argument.


Function: polydecomp (<p>, <x>)

     Decomposes the polynomial <p> in the variable <x> into the
functional composition of polynomials in <x>.  polydecomp'
returns a list [<p_1>, ..., <p_n>]' such that

lambda ([x], p_1) (lambda ([x], p_2) (... (lambda ([x], p_n) (x))
...))

is equal to <p>.  The degree of <p_i> is greater than 1 for <i>
less than <n>.

Such a decomposition is not unique.

Examples:

(%i1) polydecomp (x^210, x);
7   5   3   2
(%o1)                   [x , x , x , x ]
(%i2) p : expand (subst (x^3 - x - 1, x, x^2 - a));
6      4      3    2
(%o2)          x  - 2 x  - 2 x  + x  + 2 x - a + 1
(%i3) polydecomp (p, x);
2       3
(%o3)                 [x  - a, x  - x - 1]

The following function composes L = [e_1, ..., e_n]' as functions
in x'; it is the inverse of polydecomp:

compose (L, x) :=
block ([r : x], for e in L do r : subst (e, x, r), r) $Re-express above example using compose': (%i3) polydecomp (compose ([x^2 - a, x^3 - x - 1], x), x); 2 3 (%o3) [x - a, x - x - 1] Note that though compose (polydecomp (<p>, <x>), <x>)' always returns <p> (unexpanded), polydecomp (compose ([<p_1>, ..., <p_n>], <x>), <x>)' does not necessarily return [<p_1>, ..., <p_n>]': (%i4) polydecomp (compose ([x^2 + 2*x + 3, x^2], x), x); 2 2 (%o4) [x + 2, x + 1] (%i5) polydecomp (compose ([x^2 + x + 1, x^2 + x + 1], x), x); 2 2 x + 3 x + 5 (%o5) [------, ------, 2 x + 1] 4 2  Function: polymod   polymod (<p>) polymod (<p>, <m>) Converts the polynomial <p> to a modular representation with respect to the current modulus which is the value of the variable modulus'. polymod (<p>, <m>)' specifies a modulus <m> to be used instead of the current value of modulus'. See modulus'.  Function: quotient   quotient (<p_1>, <p_2>) quotient (<p_1>, <p_2>, <x_1>, ..., <x_n>) Returns the polynomial <p_1> divided by the polynomial <p_2>. The arguments <x_1>, ..., <x_n> are interpreted as in ratvars'. quotient' returns the first element of the two-element list returned by divide'.  Function: rat   rat (<expr>) rat (<expr>, <x_1>, ..., <x_n>) Converts <expr> to canonical rational expression (CRE) form by expanding and combining all terms over a common denominator and cancelling out the greatest common divisor of the numerator and denominator, as well as converting floating point numbers to rational numbers within a tolerance of ratepsilon'. The variables are ordered according to the <x_1>, ..., <x_n>, if specified, as in ratvars'. rat' does not generally simplify functions other than addition +', subtraction -', multiplication *', division /', and exponentiation to an integer power, whereas ratsimp' does handle those cases. Note that atoms (numbers and variables) in CRE form are not the same as they are in the general form. For example, rat(x)- x' yields rat(0)' which has a different internal representation than 0. When ratfac' is true', rat' yields a partially factored form for CRE. During rational operations the expression is maintained as fully factored as possible without an actual call to the factor package. This should always save space and may save some time in some computations. The numerator and denominator are still made relatively prime (e.g., rat((x^2 - 1)^4/(x + 1)^2)' yields (x - 1)^4 (x + 1)^2' when ratfac' is true'), but the factors within each part may not be relatively prime. ratprint' if false' suppresses the printout of the message informing the user of the conversion of floating point numbers to rational numbers. keepfloat' if true' prevents floating point numbers from being converted to rational numbers. See also ratexpand' and ratsimp'. Examples: (%i1) ((x - 2*y)^4/(x^2 - 4*y^2)^2 + 1)*(y + a)*(2*y + x) / (4*y^2 + x^2); 4 (x - 2 y) (y + a) (2 y + x) (------------ + 1) 2 2 2 (x - 4 y ) (%o1) ------------------------------------ 2 2 4 y + x (%i2) rat (%, y, a, x); 2 a + 2 y (%o2)/R/ --------- x + 2 y  Option variable: ratalgdenom   Default value: true' When ratalgdenom' is true', allows rationalization of denominators with respect to radicals to take effect. ratalgdenom' has an effect only when canonical rational expressions (CRE) are used in algebraic mode.  Function: ratcoef   ratcoef (<expr>, <x>, <n>) ratcoef (<expr>, <x>) Returns the coefficient of the expression <x>^<n>' in the expression <expr>. If omitted, <n> is assumed to be 1. The return value is free (except possibly in a non-rational sense) of the variables in <x>. If no coefficient of this type exists, 0 is returned. ratcoef' expands and rationally simplifies its first argument and thus it may produce answers different from those of coeff' which is purely syntactic. Thus ratcoef ((x + 1)/y + x, x)' returns (y + 1)/y' whereas coeff' returns 1. ratcoef (<expr>, <x>, 0)', viewing <expr> as a sum, returns a sum of those terms which do not contain <x>. Therefore if <x> occurs to any negative powers, ratcoef' should not be used. Since <expr> is rationally simplified before it is examined, coefficients may not appear quite the way they were envisioned. Example: (%i1) s: a*x + b*x + 5$
(%i2) ratcoef (s, a + b);
(%o2)                           x


Function: ratdenom (<expr>)

     Returns the denominator of <expr>, after coercing <expr> to a
canonical rational expression (CRE).  The return value is a CRE.

<expr> is coerced to a CRE by rat' if it is not already a CRE.
This conversion may change the form of <expr> by putting all terms
over a common denominator.

denom' is similar, but returns an ordinary expression instead of
a CRE.  Also, denom' does not attempt to place all terms over a
common denominator, and thus some expressions which are considered
ratios by ratdenom' are not considered ratios by denom'.


Option variable: ratdenomdivide

     Default value: true'

When ratdenomdivide' is true', ratexpand' expands a ratio in
which the numerator is a sum into a sum of ratios, all having a
common denominator.  Otherwise, ratexpand' collapses a sum of
ratios into a single ratio, the numerator of which is the sum of
the numerators of each ratio.

Examples:

(%i1) expr: (x^2 + x + 1)/(y^2 + 7);
2
x  + x + 1
(%o1)                      ----------
2
y  + 7
(%i2) ratdenomdivide: true$(%i3) ratexpand (expr); 2 x x 1 (%o3) ------ + ------ + ------ 2 2 2 y + 7 y + 7 y + 7 (%i4) ratdenomdivide: false$
(%i5) ratexpand (expr);
2
x  + x + 1
(%o5)                      ----------
2
y  + 7
(%i6) expr2: a^2/(b^2 + 3) + b/(b^2 + 3);
2
b        a
(%o6)                    ------ + ------
2        2
b  + 3   b  + 3
(%i7) ratexpand (expr2);
2
b + a
(%o7)                        ------
2
b  + 3


Function: ratdiff (<expr>, <x>)

     Differentiates the rational expression <expr> with respect to <x>.
<expr> must be a ratio of polynomials or a polynomial in <x>.  The
argument <x> may be a variable or a subexpression of <expr>.

The result is equivalent to diff', although perhaps in a
different form.  ratdiff' may be faster than diff', for rational
expressions.

ratdiff' returns a canonical rational expression (CRE) if expr'
is a CRE.  Otherwise, ratdiff' returns a general expression.

ratdiff' considers only the dependence of <expr> on <x>, and
ignores any dependencies established by depends'.

Example:

(%i1) expr: (4*x^3 + 10*x - 11)/(x^5 + 5);
3
4 x  + 10 x - 11
(%o1)                   ----------------
5
x  + 5
(%i2) ratdiff (expr, x);
7       5       4       2
8 x  + 40 x  - 55 x  - 60 x  - 50
(%o2)          - ---------------------------------
10       5
x   + 10 x  + 25
(%i3) expr: f(x)^3 - f(x)^2 + 7;
3       2
(%o3)                   f (x) - f (x) + 7
(%i4) ratdiff (expr, f(x));
2
(%o4)                   3 f (x) - 2 f(x)
(%i5) expr: (a + b)^3 + (a + b)^2;
3          2
(%o5)                  (b + a)  + (b + a)
(%i6) ratdiff (expr, a + b);
2                    2
(%o6)            3 b  + (6 a + 2) b + 3 a  + 2 a


Function: ratdisrep (<expr>)

     Returns its argument as a general expression.  If <expr> is a
general expression, it is returned unchanged.

Typically ratdisrep' is called to convert a canonical rational
expression (CRE) into a general expression.  This is sometimes
convenient if one wishes to stop the "contagion", or use rational
functions in non-rational contexts.

See also totaldisrep'.


Function: ratexpand (<expr>)

Option variable: ratexpand

     Expands <expr> by multiplying out products of sums and
exponentiated sums, combining fractions over a common denominator,
cancelling the greatest common divisor of the numerator and
denominator, then splitting the numerator (if a sum) into its
respective terms divided by the denominator.

The return value of ratexpand' is a general expression, even if
<expr> is a canonical rational expression (CRE).

The switch ratexpand' if true' will cause CRE expressions to be
fully expanded when they are converted back to general form or
displayed, while if it is false' then they will be put into a

When ratdenomdivide' is true', ratexpand' expands a ratio in
which the numerator is a sum into a sum of ratios, all having a
common denominator.  Otherwise, ratexpand' collapses a sum of
ratios into a single ratio, the numerator of which is the sum of
the numerators of each ratio.

When keepfloat' is true', prevents floating point numbers from
being rationalized when expressions which contain them are
converted to canonical rational expression (CRE) form.

Examples:

(%i1) ratexpand ((2*x - 3*y)^3);
3         2       2        3
(%o1)          - 27 y  + 54 x y  - 36 x  y + 8 x
(%i2) expr: (x - 1)/(x + 1)^2 + 1/(x - 1);
x - 1       1
(%o2)                   -------- + -----
2   x - 1
(x + 1)
(%i3) expand (expr);
x              1           1
(%o3)          ------------ - ------------ + -----
2              2             x - 1
x  + 2 x + 1   x  + 2 x + 1
(%i4) ratexpand (expr);
2
2 x                 2
(%o4)           --------------- + ---------------
3    2            3    2
x  + x  - x - 1   x  + x  - x - 1


Option variable: ratfac

     Default value: false'

When ratfac' is true', canonical rational expressions (CRE) are
manipulated in a partially factored form.

During rational operations the expression is maintained as fully
factored as possible without calling factor'.  This should always
save space and may save time in some computations.  The numerator
and denominator are made relatively prime, for example factor
((x^2 - 1)^4/(x + 1)^2)' yields (x - 1)^4 (x + 1)^2', but the
factors within each part may not be relatively prime.

In the ctensr' (Component Tensor Manipulation) package, Ricci,
Einstein, Riemann, and Weyl tensors and the scalar curvature are
factored automatically when ratfac' is true'.  ratfac' should
only be set for cases where the tensorial components are known to
consist of few terms.

The ratfac' and ratweight' schemes are incompatible and may not
both be used at the same time.


Function: ratnumer (<expr>)

     Returns the numerator of <expr>, after coercing <expr> to a
canonical rational expression (CRE).  The return value is a CRE.

<expr> is coerced to a CRE by rat' if it is not already a CRE.
This conversion may change the form of <expr> by putting all terms
over a common denominator.

num' is similar, but returns an ordinary expression instead of a
CRE.  Also, num' does not attempt to place all terms over a
common denominator, and thus some expressions which are considered
ratios by ratnumer' are not considered ratios by num'.


Function: ratp (<expr>)

     Returns true' if <expr> is a canonical rational expression (CRE)
or extended CRE, otherwise false'.

CRE are created by rat' and related functions.  Extended CRE are
created by taylor' and related functions.


Option variable: ratprint

     Default value: true'

When ratprint' is true', a message informing the user of the
conversion of floating point numbers to rational numbers is
displayed.


Function: ratsimp (<expr>)

Function: ratsimp (<expr>, <x_1>, ..., <x_n>)

     Simplifies the expression <expr> and all of its subexpressions,
including the arguments to non-rational functions.  The result is
returned as the quotient of two polynomials in a recursive form,
that is, the coefficients of the main variable are polynomials in
the other variables.  Variables may include non-rational functions
(e.g., sin (x^2 + 1)') and the arguments to any such functions
are also rationally simplified.

ratsimp (<expr>, <x_1>, ..., <x_n>)' enables rational
simplification with the specification of variable ordering as in
ratvars'.

When ratsimpexpons' is true', ratsimp' is applied to the
exponents of expressions during simplification.

See also ratexpand'.  Note that ratsimp' is affected by some of
the flags which affect ratexpand'.

Examples:

(%i1) sin (x/(x^2 + x)) = exp ((log(x) + 1)^2 - log(x)^2);
2      2
x         (log(x) + 1)  - log (x)
(%o1)        sin(------) = %e
2
x  + x
(%i2) ratsimp (%);
1          2
(%o2)                  sin(-----) = %e x
x + 1
(%i3) ((x - 1)^(3/2) - (x + 1)*sqrt(x - 1))/sqrt((x - 1)*(x + 1));
3/2
(x - 1)    - sqrt(x - 1) (x + 1)
(%o3)           --------------------------------
sqrt((x - 1) (x + 1))
(%i4) ratsimp (%);
2 sqrt(x - 1)
(%o4)                    - -------------
2
sqrt(x  - 1)
(%i5) x^(a + 1/a), ratsimpexpons: true;
2
a  + 1
------
a
(%o5)                        x


Option variable: ratsimpexpons

     Default value: false'

When ratsimpexpons' is true', ratsimp' is applied to the
exponents of expressions during simplification.


Option variable: radsubstflag

     Default value: false'

radsubstflag', if true', permits ratsubst' to make
substitutions such as u' for sqrt (x)' in x'.


Function: ratsubst (<a>, <b>, <c>)

     Substitutes <a> for <b> in <c> and returns the resulting
expression.  <b> may be a sum, product, power, etc.

ratsubst' knows something of the meaning of expressions whereas
subst' does a purely syntactic substitution.  Thus subst (a, x +
y, x + y + z)' returns x + y + z' whereas ratsubst' returns z +
a'.

When radsubstflag' is true', ratsubst' makes substitutions for
radicals in expressions which don't explicitly contain them.

ratsubst' ignores the value true' of the option variable
keepfloat'.

Examples:

(%i1) ratsubst (a, x*y^2, x^4*y^3 + x^4*y^8);
3      4
(%o1)                      a x  y + a
(%i2) cos(x)^4 + cos(x)^3 + cos(x)^2 + cos(x) + 1;
4         3         2
(%o2)       cos (x) + cos (x) + cos (x) + cos(x) + 1
(%i3) ratsubst (1 - sin(x)^2, cos(x)^2, %);
4           2                     2
(%o3)    sin (x) - 3 sin (x) + cos(x) (2 - sin (x)) + 3
(%i4) ratsubst (1 - cos(x)^2, sin(x)^2, sin(x)^4);
4           2
(%o4)                cos (x) - 2 cos (x) + 1
(%i5) radsubstflag: false$(%i6) ratsubst (u, sqrt(x), x); (%o6) x (%i7) radsubstflag: true$
(%i8) ratsubst (u, sqrt(x), x);
2
(%o8)                          u


Function: ratvars (<x_1>, ..., <x_n>)

Function: ratvars ()

System variable: ratvars

     Declares main variables <x_1>, ..., <x_n> for rational expressions.
<x_n>, if present in a rational expression, is considered the main
variable.  Otherwise, <x_[n-1]> is considered the main variable if
present, and so on through the preceding variables to <x_1>, which
is considered the main variable only if none of the succeeding
variables are present.

If a variable in a rational expression is not present in the
ratvars' list, it is given a lower priority than <x_1>.

The arguments to ratvars' can be either variables or non-rational
functions such as sin(x)'.

The variable ratvars' is a list of the arguments of the function
ratvars' when it was called most recently.  Each call to the
function ratvars' resets the list.  ratvars ()' clears the list.


Option variable: ratvarswitch

     Default value: true'

Maxima keeps an internal list in the Lisp variable VARLIST' of
the main variables for rational expressions.  If ratvarswitch' is
true', every evaluation starts with a fresh list VARLIST'.  This
is the default behavior.  Otherwise, the main variables from
previous evaluations are not removed from the internal list
VARLIST'.

The main variables, which are declared with the function ratvars'
are not affected by the option variable ratvarswitch'.

Examples:

If ratvarswitch' is true', every evaluation starts with a fresh
list VARLIST'.

(%i1) ratvarswitch:true$(%i2) rat(2*x+y^2); 2 (%o2)/R/ y + 2 x (%i3) :lisp varlist ($X $Y) (%i3) rat(2*a+b^2); 2 (%o3)/R/ b + 2 a (%i4) :lisp varlist ($A $B) If ratvarswitch' is false', the main variables from the last evaluation are still present. (%i4) ratvarswitch:false$

(%i5) rat(2*x+y^2);
2
(%o5)/R/                    y  + 2 x
(%i6) :lisp varlist
($X$Y)

(%i6) rat(2*a+b^2);
2
(%o6)/R/                    b  + 2 a

(%i7) :lisp varlist
($A$B $X$Y)


Function: ratweight

          ratweight (<x_1>, <w_1>, ..., <x_n>, <w_n>)
ratweight ()
Assigns a weight <w_i> to the variable <x_i>.  This causes a term
to be replaced by 0 if its weight exceeds the value of the
variable ratwtlvl' (default yields no truncation).  The weight of
a term is the sum of the products of the weight of a variable in
the term times its power.  For example, the weight of 3 x_1^2
x_2' is 2 w_1 + w_2'.  Truncation according to ratwtlvl' is
carried out only when multiplying or exponentiating canonical
rational expressions (CRE).

ratweight ()' returns the cumulative list of weight assignments.

Note: The ratfac' and ratweight' schemes are incompatible and may
not both be used at the same time.

Examples:

(%i1) ratweight (a, 1, b, 1);
(%o1)                     [a, 1, b, 1]
(%i2) expr1: rat(a + b + 1)$(%i3) expr1^2; 2 2 (%o3)/R/ b + (2 a + 2) b + a + 2 a + 1 (%i4) ratwtlvl: 1$
(%i5) expr1^2;
(%o5)/R/                  2 b + 2 a + 1


System variable: ratweights

     Default value: []'

ratweights' is the list of weights assigned by ratweight'.  The
list is cumulative: each call to ratweight' places additional
items in the list.

kill (ratweights)' and save (ratweights)' both work as expected.


Option variable: ratwtlvl

     Default value: false'

ratwtlvl' is used in combination with the ratweight' function to
control the truncation of canonical rational expressions (CRE).
For the default value of false', no truncation occurs.


Function: remainder

          remainder (<p_1>, <p_2>)
remainder (<p_1>, <p_2>, <x_1>, ..., <x_n>)
Returns the remainder of the polynomial <p_1> divided by the
polynomial <p_2>.  The arguments <x_1>, ..., <x_n> are interpreted
as in ratvars'.

remainder' returns the second element of the two-element list
returned by divide'.


Function: resultant (<p_1>, <p_2>, <x>)

     The function resultant' computes the resultant of the two
polynomials <p_1> and <p_2>, eliminating the variable <x>.  The
resultant is a determinant of the coefficients of <x> in <p_1> and
<p_2>, which equals zero if and only if <p_1> and <p_2> have a
non-constant factor in common.

If <p_1> or <p_2> can be factored, it may be desirable to call
factor' before calling resultant'.

The option variable resultant' controls which algorithm will be
used to compute the resultant.  See the option variable
resultant'.

The function bezout' takes the same arguments as resultant' and
returns a matrix.  The determinant of the return value is the
desired resultant.

Examples:

(%i1) resultant(2*x^2+3*x+1, 2*x^2+x+1, x);
(%o1)                           8
(%i2) resultant(x+1, x+1, x);
(%o2)                           0
(%i3) resultant((x+1)*x, (x+1), x);
(%o3)                           0
(%i4) resultant(a*x^2+b*x+1, c*x + 2, x);
2
(%o4)                   c  - 2 b c + 4 a

(%i5) bezout(a*x^2+b*x+1, c*x+2, x);
[ 2 a  2 b - c ]
(%o5)                   [              ]
[  c      2    ]
(%i6) determinant(%);
(%o6)                   4 a - (2 b - c) c


Option variable: resultant

     Default value: subres'

The option variable resultant' controls which algorithm will be
used to compute the resultant with the function resultant'.  The
possible values are:

subres'
for the subresultant polynomial remainder sequence (PRS)
algorithm,

mod'
for the modular resultant algorithm, and

red'
for the reduced polynomial remainder sequence (PRS) algorithm.

On most problems the default value subres' should be best.  On
some large degree univariate or bivariate problems mod' may be
better.


Option variable: savefactors

     Default value: false'

When savefactors' is true', causes the factors of an expression
which is a product of factors to be saved by certain functions in
order to speed up later factorizations of expressions containing
some of the same factors.


Function: showratvars (<expr>)

     Returns a list of the canonical rational expression (CRE)
variables in expression expr'.


Function: sqfr (<expr>)

     is similar to factor' except that the polynomial factors are
"square-free."  That is, they have factors only of degree one.
This algorithm, which is also used by the first stage of factor',
utilizes the fact that a polynomial has in common with its n'th
derivative all its factors of degree greater than n.  Thus by
taking greatest common divisors with the polynomial of the
derivatives with respect to each variable in the polynomial, all
factors of degree greater than 1 can be found.

Example:

(%i1) sqfr (4*x^4 + 4*x^3 - 3*x^2 - 4*x - 1);
2   2
(%o1)                  (2 x + 1)  (x  - 1)


Function: tellrat

          tellrat (<p_1>, ..., <p_n>)
tellrat ()
Adds to the ring of algebraic integers known to Maxima the
elements which are the solutions of the polynomials <p_1>, ...,
<p_n>.  Each argument <p_i> is a polynomial with integer
coefficients.

tellrat (<x>)' effectively means substitute 0 for <x> in rational
functions.

tellrat ()' returns a list of the current substitutions.

algebraic' must be set to true' in order for the simplification
of algebraic integers to take effect.

Maxima initially knows about the imaginary unit %i' and all roots
of integers.

There is a command untellrat' which takes kernels and removes
tellrat' properties.

When tellrat''ing a multivariate polynomial, e.g., tellrat (x^2
- y^2)', there would be an ambiguity as to whether to substitute
<y>^2' for <x>^2' or vice versa.  Maxima picks a particular
ordering, but if the user wants to specify which, e.g.  tellrat
(y^2 = x^2)' provides a syntax which says replace <y>^2' by
<x>^2'.

Examples:

(%i1) 10*(%i + 1)/(%i + 3^(1/3));
10 (%i + 1)
(%o1)                      -----------
1/3
%i + 3
(%i2) ev (ratdisrep (rat(%)), algebraic);
2/3      1/3              2/3      1/3
(%o2)    (4 3    - 2 3    - 4) %i + 2 3    + 4 3    - 2
(%i3) tellrat (1 + a + a^2);
2
(%o3)                     [a  + a + 1]
(%i4) 1/(a*sqrt(2) - 1) + a/(sqrt(3) + sqrt(2));
1                 a
(%o4)           ------------- + -----------------
sqrt(2) a - 1   sqrt(3) + sqrt(2)
(%i5) ev (ratdisrep (rat(%)), algebraic);
(7 sqrt(3) - 10 sqrt(2) + 2) a - 2 sqrt(2) - 1
(%o5)    ----------------------------------------------
7
(%i6) tellrat (y^2 = x^2);
2    2   2
(%o6)                 [y  - x , a  + a + 1]


Function: totaldisrep (<expr>)

     Converts every subexpression of <expr> from canonical rational
expressions (CRE) to general form and returns the result.  If
<expr> is itself in CRE form then totaldisrep' is identical to
ratdisrep'.

totaldisrep' may be useful for ratdisrepping expressions such as
equations, lists, matrices, etc., which have some subexpressions
in CRE form.


Function: untellrat (<x_1>, ..., <x_n>)

     Removes tellrat' properties from <x_1>, ..., <x_n>.



## 15 Special Functions


Introduction to Special Functions
Bessel Functions
Airy Functions
Gamma and factorial Functions
Exponential Integrals
Error Function
Struve Functions
Hypergeometric Functions
Parabolic Cylinder Functions
Functions and Variables for Special Functions


## 15.1 Introduction to Special Functions

Special function notation follows:

bessel_j (index, expr)         Bessel function, 1st kind
bessel_y (index, expr)         Bessel function, 2nd kind
bessel_i (index, expr)         Modified Bessel function, 1st kind
bessel_k (index, expr)         Modified Bessel function, 2nd kind

hankel_1 (v,z)                 Hankel function of the 1st kind
hankel_2 (v,z)                 Hankel function of the 2nd kind
struve_h (v,z)                 Struve H function
struve_l (v,z)                 Struve L function

assoc_legendre_p[v,u] (z)      Legendre function of degree v and order u
assoc_legendre_q[v,u] (z)      Legendre function, 2nd kind

%f[p,q] ([], [], expr)         Generalized Hypergeometric function
gamma (z)                      Gamma function
gamma_greek (a,z)              Incomplete gamma function
gamma_incomplete (a,z)         Tail of incomplete gamma function
hypergeometric (l1, l2, z)     Hypergeometric function
slommel
%m[u,k] (z)                    Whittaker function, 1st kind
%w[u,k] (z)                    Whittaker function, 2nd kind
erfc (z)                       Complement of the erf function

expintegral_e (v,z)            Exponential integral E
expintegral_e1 (z)             Exponential integral E1
expintegral_ei (z)             Exponential integral Ei
expintegral_li (z)             Logarithmic integral Li
expintegral_si (z)             Exponential integral Si
expintegral_ci (z)             Exponential integral Ci
expintegral_shi (z)            Exponential integral Shi
expintegral_chi (z)            Exponential integral Chi

kelliptic (z)                  Complete elliptic integral of the first
kind (K)
parabolic_cylinder_d (v,z)     Parabolic cylinder D function


## 15.2 Bessel Functions

Function: bessel_j (<v>, <z>)

     The Bessel function of the first kind of order v and argument z.

bessel_j' is defined as

inf
====       k  - v - 2 k  v + 2 k
\     (- 1)  2          z
>    --------------------------
/        k! gamma(v + k + 1)
====
k = 0

although the infinite series is not used for computations.


Function: bessel_y (<v>, <z>)

     The Bessel function of the second kind of order v and argument z.

bessel_y' is defined as
cos(%pi v) bessel_j(v, z) - bessel_j(-v, z)
-------------------------------------------
sin(%pi v)

when v is not an integer.  When v is an integer n, the limit as v
approaches n is taken.


Function: bessel_i (<v>, <z>)

     The modified Bessel function of the first kind of order v and
argument z.

bessel_i' is defined as
inf
====   - v - 2 k  v + 2 k
\     2          z
>    -------------------
/     k! gamma(v + k + 1)
====
k = 0

although the infinite series is not used for computations.


Function: bessel_k (<v>, <z>)

     The modified Bessel function of the second kind of order v and
argument z.

bessel_k' is defined as
%pi csc(%pi v) (bessel_i(-v, z) - bessel_i(v, z))
-------------------------------------------------
2

when v is not an integer.  If v is an integer n, then the limit as
v approaches n is taken.


Function: hankel_1 (<v>, <z>)

     The Hankel function of the first kind of order v and argument z
(A&S 9.1.3). hankel_1' is defined as

bessel_j(v,z) + %i * bessel_y(v,z)

Maxima evaluates hankel_1' numerically for a complex order v and
complex argument z in float precision. The numerical evaluation in
bigfloat precision is not supported.

When besselexpand' is true', hankel_1' is expanded in terms of
elementary functions when the order v is half of an odd integer.
See besselexpand'.

Maxima knows the derivative of hankel_1' wrt the argument z.

Examples:

Numerical evaluation:

(%i1) hankel_1(1,0.5);
(%o1)        0.24226845767487 - 1.471472392670243 %i
(%i2) hankel_1(1,0.5+%i);
(%o2)       - 0.25582879948621 %i - 0.23957560188301

Expansion of hankel_1' when besselexpand' is true':

(%i1) hankel_1(1/2,z),besselexpand:true;
sqrt(2) sin(z) - sqrt(2) %i cos(z)
(%o1)          ----------------------------------
sqrt(%pi) sqrt(z)

Derivative of hankel_1' wrt the argument z. The derivative wrt the
order v is not supported. Maxima returns a noun form:

(%i1) diff(hankel_1(v,z),z);
hankel_1(v - 1, z) - hankel_1(v + 1, z)
(%o1)        ---------------------------------------
2
(%i2) diff(hankel_1(v,z),v);
d
(%o2)                  -- (hankel_1(v, z))
dv


Function: hankel_2 (<v>, <z>)

     The Hankel function of the second kind of order v and argument z
(A&S 9.1.4). hankel_2' is defined as

bessel_j(v,z) - %i * bessel_y(v,z)

Maxima evaluates hankel_2' numerically for a complex order v and
complex argument z in float precision. The numerical evaluation in
bigfloat precision is not supported.

When besselexpand' is true', hankel_2' is expanded in terms of
elementary functions when the order v is half of an odd integer.
See besselexpand'.

Maxima knows the derivative of hankel_2' wrt the argument z.

For examples see hankel_1'.


Option variable: besselexpand

     Default value: false'

Controls expansion of the Bessel functions when the order is half
of an odd integer.  In this case, the Bessel functions can be
expanded in terms of other elementary functions.  When
besselexpand' is true', the Bessel function is expanded.

(%i1) besselexpand: false$(%i2) bessel_j (3/2, z); 3 (%o2) bessel_j(-, z) 2 (%i3) besselexpand: true$
(%i4) bessel_j (3/2, z);
sin(z)   cos(z)
sqrt(2) sqrt(z) (------ - ------)
2       z
z
(%o4)                  ---------------------------------
sqrt(%pi)


Function: scaled_bessel_i (<v>, <z>)

     The scaled modified Bessel function of the first kind of order v
and argument z.  That is, scaled_bessel_i(v,z) =
exp(-abs(z))*bessel_i(v, z).  This function is particularly useful
for calculating bessel_i for large z, which is large.  However,
symbolic work, it is probably preferable to work with the
expression exp(-abs(z))*bessel_i(v, z)'.


Function: scaled_bessel_i0 (<z>)

     Identical to scaled_bessel_i(0,z)'.


Function: scaled_bessel_i1 (<z>)

     Identical to scaled_bessel_i(1,z)'.


Function: %s [<u>,<v>] (<z>)

     Lommel's little s[u,v](z) function.  Probably Gradshteyn & Ryzhik
8.570.1.



## 15.3 Airy Functions

The Airy functions Ai(x) and Bi(x) are defined in Abramowitz and Stegun,
Handbook of Mathematical Functions, Section 10.4.

y = Ai(x)' and y = Bi(x)' are two linearly independent solutions
of the Airy differential equation diff (y(x), x, 2) - x y(x) = 0'.

If the argument x' is a real or complex floating point number, the
numerical value of the function is returned.

Function: airy_ai (<x>)

     The Airy function Ai(x).  (A&S 10.4.2)

The derivative diff (airy_ai(x), x)' is airy_dai(x)'.

See also airy_bi', airy_dai', airy_dbi'.


Function: airy_dai (<x>)

     The derivative of the Airy function Ai airy_ai(x)'.

See airy_ai'.


Function: airy_bi (<x>)

     The Airy function Bi(x).  (A&S 10.4.3)

The derivative diff (airy_bi(x), x)' is airy_dbi(x)'.

See airy_ai', airy_dbi'.


Function: airy_dbi (<x>)

     The derivative of the Airy Bi function airy_bi(x)'.

See airy_ai' and airy_bi'.



## 15.4 Gamma and factorial Functions

The gamma function and the related beta, psi and incomplete gamma
functions are defined in Abramowitz and Stegun, Handbook of
Mathematical Functions, Chapter 6.

Function: bffac (<expr>, <n>)

     Bigfloat version of the factorial (shifted gamma) function.  The
second argument is how many digits to retain and return, it's a
good idea to request a couple of extra.


Function: bfpsi (<n>, <z>, <fpprec>)

Function: bfpsi0 (<z>, <fpprec>)

     bfpsi' is the polygamma function of real argument <z> and integer
order <n>.  bfpsi0' is the digamma function.  bfpsi0 (<z>,
<fpprec>)' is equivalent to bfpsi (0, <z>, <fpprec>)'.

These functions return bigfloat values.  <fpprec> is the bigfloat
precision of the return value.


Function: cbffac (<z>, <fpprec>)

     Complex bigfloat factorial.


Function: gamma (<z>)

     The basic definition of the gamma function (A&S 6.1.1) is

inf
/
[     z - 1   - t
gamma(z) = I    t      %e    dt
]
/
0

Maxima simplifies gamma' for positive integer and positive and
negative rational numbers. For half integral values the result is
a rational number times sqrt(%pi)'. The simplification for
integer values is controlled by factlim'. For integers greater
than factlim' the numerical result of the factorial function,
which is used to calculate gamma', will overflow.  The
simplification for rational numbers is controlled by gammalim' to
avoid internal overflow. See factlim' and gammalim'.

For negative integers gamma' is not defined.

Maxima can evalute gamma' numerically for real and complex values
in float and bigfloat precision.

gamma' has mirror symmetry.

When gamma_expand' is true', Maxima expands gamma' for
arguments z+n' and z-n' where n' is an integer.

Maxima knows the derivate of gamma'.

Examples:

Simplification for integer, half integral, and rational numbers:

(%i1) map('gamma,[1,2,3,4,5,6,7,8,9]);
(%o1)        [1, 1, 2, 6, 24, 120, 720, 5040, 40320]
(%i2) map('gamma,[1/2,3/2,5/2,7/2]);
sqrt(%pi)  3 sqrt(%pi)  15 sqrt(%pi)
(%o2)   [sqrt(%pi), ---------, -----------, ------------]
2           4            8
(%i3) map('gamma,[2/3,5/3,7/3]);
2           1
2 gamma(-)  4 gamma(-)
2           3           3
(%o3)          [gamma(-), ----------, ----------]
3       3           9

Numerical evaluation for real and complex values:

(%i4) map('gamma,[2.5,2.5b0]);
(%o4)     [1.329340388179137, 1.3293403881791370205b0]
(%i5) map('gamma,[1.0+%i,1.0b0+%i]);
(%o5) [0.498015668118356 - .1549498283018107 %i,
4.9801566811835604272b-1 - 1.5494982830181068513b-1 %i]

gamma' has mirror symmetry:

(%i6) declare(z,complex)$(%i7) conjugate(gamma(z)); (%o7) gamma(conjugate(z)) Maxima expands gamma(z+n)' and gamma(z-n)', when gamma_expand' is true': (%i8) gamma_expand:true$

(%i9) [gamma(z+1),gamma(z-1),gamma(z+2)/gamma(z+1)];
gamma(z)
(%o9)             [z gamma(z), --------, z + 1]
z - 1

The deriviative of gamma':

(%i10) diff(gamma(z),z);
(%o10)                  psi (z) gamma(z)
0

See also makegamma'.

The Euler-Mascheroni constant is %gamma'.


Function: log_gamma (<z>)

     The natural logarithm of the gamma function.


Function: gamma_greek (<a>, <z>)

     The lower incomplete gamma function (A&S 6.5.2):

z
/
[  a - 1   - t
gamma_greek(a, z) = I t      %e    dt
]
/
0

See also gamma_incomplete' (upper incomplete gamma function).


Function: gamma_incomplete (<a>, <z>)

     The incomplete upper gamma function A&S 6.5.3:

inf
/
[     a - 1   - t
gamma_incomplete(a, z) = I    t      %e    dt
]
/
z

See also gamma_expand' for controlling how gamma_incomplete' is
expressed in terms of elementary functions and erfc'.

Also see the related functions gamma_incomplete_regularized' and
gamma_incomplete_generalized'.


Function: gamma_incomplete_regularized (<a>, <z>)

     The regularized incomplete upper gamma function A&S 6.5.1:

gamma_incomplete_regularized(a, z) =
gamma_incomplete(a, z)
----------------------
gamma(a)

See also gamma_expand' for controlling how gamma_incomplete' is
expressed in terms of elementary functions and erfc'.

Also see gamma_incomplete'.


Function: gamma_incomplete_generalized (<a>, <z1>, <z1>)

     The generalized incomplete gamma function.

gamma_incomplete_generalized(a, z1, z2) =
z2
/
[    a - 1   - t
I   t      %e    dt
]
/
z1

Also see gamma_incomplete' and gamma_incomplete_regularized'.


Option variable: gamma_expand

     Default value: false'

gamma_expand' controls expansion of gamma_incomplete'.  When
gamma_expand' is true', gamma_incomplete(v,z)' is expanded in
terms of z', exp(z)', and erfc(z)' when possible.

(%i1) gamma_incomplete(2,z);
(%o1)                       gamma_incomplete(2, z)
(%i2) gamma_expand:true;
(%o2)                                true
(%i3) gamma_incomplete(2,z);
- z
(%o3)                            (z + 1) %e
(%i4) gamma_incomplete(3/2,z);
- z   sqrt(%pi) erfc(sqrt(z))
(%o4)               sqrt(z) %e    + -----------------------
2


Option variable: gammalim

     Default value: 10000

gammalim' controls simplification of the gamma function for
integral and rational number arguments.  If the absolute value of
the argument is not greater than gammalim', then simplification
will occur.  Note that the factlim' switch controls
simplification of the result of gamma' of an integer argument as
well.


Function: makegamma (<expr>)

     Transforms instances of binomial, factorial, and beta functions in
<expr> into gamma functions.


Function: beta (<a>, <b>)

     The beta function is defined as gamma(a) gamma(b)/gamma(a+b)'
(A&S 6.2.1).

Maxima simplifies the beta function for positive integers and
rational numbers, which sum to an integer. When
beta_args_sum_to_integer' is true', Maxima simplifies also
general expressions which sum to an integer.

For <a> or <b> equal to zero the beta function is not defined.

In general the beta function is not defined for negative integers
as an argument. The exception is for <a=-n>, <n> a positive integer
and <b> a positive integer with <b<=n>, it is possible to define an
analytic continuation. Maxima gives for this case a result.

When beta_expand' is true', expressions like beta(a+n,b)' and
beta(a-n,b)' or beta(a,b+n)' and beta(a,b-n)' with n' an
integer are simplified.

Maxima can evaluate the beta function for real and complex values
in float and bigfloat precision. For numerical evaluation Maxima
uses log_gamma':

- log_gamma(b + a) + log_gamma(b) + log_gamma(a)
%e

Maxima knows that the beta function is symmetric and has mirror
symmetry.

Maxima knows the derivatives of the beta function with respect to
<a> or <b>.

To express the beta function as a ratio of gamma functions see
makegamma'.

Examples:

Simplification, when one of the arguments is an integer:

(%i1) [beta(2,3),beta(2,1/3),beta(2,a)];
1   9      1
(%o1)                         [--, -, ---------]
12  4  a (a + 1)

Simplification for two rational numbers as arguments which sum to
an integer:

(%i2) [beta(1/2,5/2),beta(1/3,2/3),beta(1/4,3/4)];
3 %pi   2 %pi
(%o2)                    [-----, -------, sqrt(2) %pi]
8    sqrt(3)

When setting beta_args_sum_to_integer' to true' more general
expression are simplified, when the sum of the arguments is an
integer:

(%i3) beta_args_sum_to_integer:true$(%i4) beta(a+1,-a+2); %pi (a - 1) a (%o4) ------------------ 2 sin(%pi (2 - a)) The possible results, when one of the arguments is a negative integer: (%i5) [beta(-3,1),beta(-3,2),beta(-3,3)]; 1 1 1 (%o5) [- -, -, - -] 3 6 3 beta(a+n,b)' or beta(a-n)' with n' an integer simplifies when beta_expand' is true': (%i6) beta_expand:true$
(%i7) [beta(a+1,b),beta(a-1,b),beta(a+1,b)/beta(a,b+1)];
a beta(a, b)  beta(a, b) (b + a - 1)  a
(%o7)              [------------, ----------------------, -]
b + a              a - 1           b

Beta is not defined, when one of the arguments is zero:

(%i7) beta(0,b);
beta: expected nonzero arguments; found 0, b
-- an error.  To debug this try debugmode(true);

Numercial evaluation for real and complex arguments in float or
bigfloat precision:

(%i8) beta(2.5,2.3);
(%o8) .08694748611299981

(%i9) beta(2.5,1.4+%i);
(%o9) 0.0640144950796695 - .1502078053286415 %i

(%i10) beta(2.5b0,2.3b0);
(%o10) 8.694748611299969b-2

(%i11) beta(2.5b0,1.4b0+%i);
(%o11) 6.401449507966944b-2 - 1.502078053286415b-1 %i

Beta is symmetric and has mirror symmetry:

(%i14) beta(a,b)-beta(b,a);
(%o14)                                 0
(%i15) declare(a,complex,b,complex)$(%i16) conjugate(beta(a,b)); (%o16) beta(conjugate(a), conjugate(b)) The derivative of the beta function wrt a': (%i17) diff(beta(a,b),a); (%o17) - beta(a, b) (psi (b + a) - psi (a)) 0 0  Function: beta_incomplete (<a>, <b>, <z>)   The basic definition of the incomplete beta function (A&S 6.6.1) is z / [ b - 1 a - 1 I (1 - t) t dt ] / 0 This definition is possible for realpart(a)>0 and realpart(b)>0 and abs(z)<1. For other values the incomplete beta function can be defined through a generalized hypergeometric function: gamma(a) hypergeometric_generalized([a, 1 - b], [a + 1], z) z (See functions.wolfram.com for a complete definition of the incomplete beta function.) For negative integers a = -n and positive integers b=m with m<=n the incomplete beta function is defined through m - 1 k ==== (1 - m) z n - 1 \ k z > ----------- / k! (n - k) ==== k = 0 Maxima uses this definition to simplify beta_incomplete' for <a> a negative integer. For <a> a positive integer, beta_incomplete' simplifies for any argument <b> and <z> and for <b> a positive integer for any argument <a> and <z>, with the exception of <a> a negative integer. For z=0 and realpart(a)>0, beta_incomplete' has the specific value zero. For <z=1> and realpart(b)>0, beta_incomplete' simplifies to the beta function beta(a,b)'. Maxima evaluates beta_incomplete' numerically for real and complex values in float or bigfloat precision. For the numerical evaluation an expansion of the incomplete beta function in continued fractions is used. When the option variable beta_expand' is true', Maxima expands expressions like beta_incomplete(a+n,b,z)' and beta_incomplete(a-n,b,z)' where n is a positive integer. Maxima knows the derivatives of beta_incomplete' with respect to the variables <a>, <b> and <z> and the integral with respect to the variable <z>. Examples: Simplification for <a> a positive integer: (%i1) beta_incomplete(2,b,z); b 1 - (1 - z) (b z + 1) (%o1) ---------------------- b (b + 1) Simplification for <b> a positive integer: (%i2) beta_incomplete(a,2,z); a (a (1 - z) + 1) z (%o2) ------------------ a (a + 1) Simplification for <a> and <b> a positive integer: (%i3) beta_incomplete(3,2,z); 3 (3 (1 - z) + 1) z (%o3) ------------------ 12 <a> is a negative integer and b<=(-a), Maxima simplifies: (%i4) beta_incomplete(-3,1,z); 1 (%o4) - ---- 3 3 z For the specific values z=0 and z=1, Maxima simplifies: (%i5) assume(a>0,b>0)$
(%i6) beta_incomplete(a,b,0);
(%o6)                                 0
(%i7) beta_incomplete(a,b,1);
(%o7)                            beta(a, b)

Numerical evaluation in float or bigfloat precision:

(%i8) beta_incomplete(0.25,0.50,0.9);
(%o8)                          4.594959440269333
(%i9)  fpprec:25$(%i10) beta_incomplete(0.25,0.50,0.9b0); (%o10) 4.594959440269324086971203b0 For abs(z)>1 beta_incomplete' returns a complex result: (%i11) beta_incomplete(0.25,0.50,1.7); (%o11) 5.244115108584249 - 1.45518047787844 %i Results for more general complex arguments: (%i14) beta_incomplete(0.25+%i,1.0+%i,1.7+%i); (%o14) 2.726960675662536 - .3831175704269199 %i (%i15) beta_incomplete(1/2,5/4*%i,2.8+%i); (%o15) 13.04649635168716 %i - 5.802067956270001 (%i16) Expansion, when beta_expand' is true': (%i23) beta_incomplete(a+1,b,z),beta_expand:true; b a a beta_incomplete(a, b, z) (1 - z) z (%o23) -------------------------- - ----------- b + a b + a (%i24) beta_incomplete(a-1,b,z),beta_expand:true; b a - 1 beta_incomplete(a, b, z) (- b - a + 1) (1 - z) z (%o24) -------------------------------------- - --------------- 1 - a 1 - a Derivative and integral for beta_incomplete': (%i34) diff(beta_incomplete(a, b, z), z); b - 1 a - 1 (%o34) (1 - z) z (%i35) integrate(beta_incomplete(a, b, z), z); b a (1 - z) z (%o35) ----------- + beta_incomplete(a, b, z) z b + a a beta_incomplete(a, b, z) - -------------------------- b + a (%i36) factor(diff(%, z)); (%o36) beta_incomplete(a, b, z)  Function: beta_incomplete_regularized (<a>, <b>, <z>)   The regularized incomplete beta function A&S 6.6.2, defined as beta_incomplete_regularized(a, b, z) = beta_incomplete(a, b, z) ------------------------ beta(a, b) As for beta_incomplete' this definition is not complete. See functions.wolfram.com for a complete definition of beta_incomplete_regularized'. beta_incomplete_regularized' simplifies <a> or <b> a positive integer. For z=0 and realpart(a)>0, beta_incomplete_regularized' has the specific value 0. For <z=1> and realpart(b)>0, beta_incomplete_regularized' simplifies to 1. Maxima can evaluate beta_incomplete_regularized' for real and complex arguments in float and bigfloat precision. When beta_expand' is true', Maxima expands beta_incomplete_regularized' for arguments a+n or a-n, where n is an integer. Maxima knows the derivatives of beta_incomplete_regularized' with respect to the variables <a>, <b>, and <z> and the integral with respect to the variable <z>. Examples: Simplification for <a> or <b> a positive integer: (%i1) beta_incomplete_regularized(2,b,z); b (%o1) 1 - (1 - z) (b z + 1) (%i2) beta_incomplete_regularized(a,2,z); a (%o2) (a (1 - z) + 1) z (%i3) beta_incomplete_regularized(3,2,z); 3 (%o3) (3 (1 - z) + 1) z For the specific values z=0 and z=1, Maxima simplifies: (%i4) assume(a>0,b>0)$
(%i5) beta_incomplete_regularized(a,b,0);
(%o5)                                 0
(%i6) beta_incomplete_regularized(a,b,1);
(%o6)                                 1

Numerical evaluation for real and complex arguments in float and
bigfloat precision:

(%i7) beta_incomplete_regularized(0.12,0.43,0.9);
(%o7)                         .9114011367359802
(%i8) fpprec:32$(%i9) beta_incomplete_regularized(0.12,0.43,0.9b0); (%o9) 9.1140113673598075519946998779975b-1 (%i10) beta_incomplete_regularized(1+%i,3/3,1.5*%i); (%o10) .2865367499935403 %i - 0.122995963334684 (%i11) fpprec:20$
(%i12) beta_incomplete_regularized(1+%i,3/3,1.5b0*%i);
(%o12)      2.8653674999354036142b-1 %i - 1.2299596333468400163b-1

Expansion, when beta_expand' is true':

(%i13) beta_incomplete_regularized(a+1,b,z);
b  a
(1 - z)  z
(%o13) beta_incomplete_regularized(a, b, z) - ------------
a beta(a, b)
(%i14) beta_incomplete_regularized(a-1,b,z);
(%o14) beta_incomplete_regularized(a, b, z)
b  a - 1
(1 - z)  z
- ----------------------
beta(a, b) (b + a - 1)

The derivative and the integral wrt <z>:

(%i15) diff(beta_incomplete_regularized(a,b,z),z);
b - 1  a - 1
(1 - z)      z
(%o15)                 -------------------
beta(a, b)
(%i16) integrate(beta_incomplete_regularized(a,b,z),z);
(%o16) beta_incomplete_regularized(a, b, z) z
b  a
(1 - z)  z
a (beta_incomplete_regularized(a, b, z) - ------------)
a beta(a, b)
- -------------------------------------------------------
b + a


Function: beta_incomplete_generalized (<a>, <b>, <z1>, <z2>)

     The basic definition of the generalized incomplete beta function is

z2
/
[          b - 1  a - 1
I   (1 - t)      t      dt
]
/
z1

Maxima simplifies beta_incomplete_regularized' for <a> and <b> a
positive integer.

For realpart(a)>0 and z1=0 or z2=0, Maxima simplifies
beta_incomplete_generalized' to beta_incomplete'. For
realpart(b)>0 and z1=1 or <z2=1>, Maxima simplifies to an
expression with beta' and beta_incomplete'.

Maxima evaluates beta_incomplete_regularized' for real and
complex values in float and bigfloat precision.

When beta_expand' is true', Maxima expands
beta_incomplete_generalized' for a+n and a-n, <n> a positive
integer.

Maxima knows the derivative of beta_incomplete_generalized' with
respect to the variables <a>, <b>, <z1>, and <z2> and the
integrals with respect to the variables <z1> and <z2>.

Examples:

Maxima simplifies beta_incomplete_generalized' for <a> and <b> a
positive integer:

(%i1) beta_incomplete_generalized(2,b,z1,z2);
b                      b
(1 - z1)  (b z1 + 1) - (1 - z2)  (b z2 + 1)
(%o1)      -------------------------------------------
b (b + 1)
(%i2) beta_incomplete_generalized(a,2,z1,z2);
a                      a
(a (1 - z2) + 1) z2  - (a (1 - z1) + 1) z1
(%o2)      -------------------------------------------
a (a + 1)
(%i3) beta_incomplete_generalized(3,2,z1,z2);
2      2                       2      2
(1 - z1)  (3 z1  + 2 z1 + 1) - (1 - z2)  (3 z2  + 2 z2 + 1)
(%o3) -----------------------------------------------------------
12

Simplification for specific values z1=0, z2=0, z1=1, or z2=1:

(%i4) assume(a > 0, b > 0)$(%i5) beta_incomplete_generalized(a,b,z1,0); (%o5) - beta_incomplete(a, b, z1) (%i6) beta_incomplete_generalized(a,b,0,z2); (%o6) - beta_incomplete(a, b, z2) (%i7) beta_incomplete_generalized(a,b,z1,1); (%o7) beta(a, b) - beta_incomplete(a, b, z1) (%i8) beta_incomplete_generalized(a,b,1,z2); (%o8) beta_incomplete(a, b, z2) - beta(a, b) Numerical evaluation for real arguments in float or bigfloat precision: (%i9) beta_incomplete_generalized(1/2,3/2,0.25,0.31); (%o9) .09638178086368676 (%i10) fpprec:32$
(%i10) beta_incomplete_generalized(1/2,3/2,0.25,0.31b0);
(%o10)               9.6381780863686935309170054689964b-2

Numerical evaluation for complex arguments in float or bigfloat
precision:

(%i11) beta_incomplete_generalized(1/2+%i,3/2+%i,0.25,0.31);
(%o11)           - .09625463003205376 %i - .003323847735353769
(%i12) fpprec:20$(%i13) beta_incomplete_generalized(1/2+%i,3/2+%i,0.25,0.31b0); (%o13) - 9.6254630032054178691b-2 %i - 3.3238477353543591914b-3 Expansion for a+n or a-n, <n> a positive integer, when beta_expand' is true': (%i14) beta_expand:true$

(%i15) beta_incomplete_generalized(a+1,b,z1,z2);

b   a           b   a
(1 - z1)  z1  - (1 - z2)  z2
(%o15) -----------------------------
b + a
a beta_incomplete_generalized(a, b, z1, z2)
+ -------------------------------------------
b + a
(%i16) beta_incomplete_generalized(a-1,b,z1,z2);

beta_incomplete_generalized(a, b, z1, z2) (- b - a + 1)
(%o16) -------------------------------------------------------
1 - a
b   a - 1           b   a - 1
(1 - z2)  z2      - (1 - z1)  z1
- -------------------------------------
1 - a

Derivative wrt the variable <z1> and integrals wrt <z1> and <z2>:

(%i17) diff(beta_incomplete_generalized(a,b,z1,z2),z1);
b - 1   a - 1
(%o17)               - (1 - z1)      z1
(%i18) integrate(beta_incomplete_generalized(a,b,z1,z2),z1);
(%o18) beta_incomplete_generalized(a, b, z1, z2) z1
+ beta_incomplete(a + 1, b, z1)
(%i19) integrate(beta_incomplete_generalized(a,b,z1,z2),z2);
(%o19) beta_incomplete_generalized(a, b, z1, z2) z2
- beta_incomplete(a + 1, b, z2)


Option variable: beta_expand

     Default value: false

When beta_expand' is true', beta(a,b)' and related functions
are expanded for arguments like a+n or a-n, where n is an integer.


Option variable: beta_args_sum_to_integer

     Default value: false

When beta_args_sum_to_integer' is true', Maxima simplifies
beta(a,b)', when the arguments <a> and <b> sum to an integer.


Function: psi [<n>](<x>)

     The derivative of log (gamma (<x>))' of order <n>+1'.  Thus,
psi(<x>)' is the first derivative, psi(<x>)' is the second
derivative, etc.

Maxima does not know how, in general, to compute a numerical value
of psi', but it can compute some exact values for rational args.
Several variables control what range of rational args psi' will
return an exact value, if possible.  See maxpsiposint',
maxpsinegint', maxpsifracnum', and maxpsifracdenom'.  That is,
<x> must lie between maxpsinegint' and maxpsiposint'.  If the
absolute value of the fractional part of <x> is rational and has a
numerator less than maxpsifracnum' and has a denominator less
than maxpsifracdenom', psi' will return an exact value.

The function bfpsi' in the bffac' package can compute numerical
values.


Option variable: maxpsiposint

     Default value: 20

maxpsiposint' is the largest positive value for which psi[n](x)'
will try to compute an exact value.


Option variable: maxpsinegint

     Default value: -10

maxpsinegint' is the most negative value for which psi[n](x)'
will try to compute an exact value.  That is if <x> is less than
maxnegint', psi[n](<x>)' will not return simplified answer, even
if it could.


Option variable: maxpsifracnum

     Default value: 6

Let <x> be a rational number less than one of the form p/q'.  If
p' is greater than maxpsifracnum', then psi[<n>](<x>)' will not
try to return a simplified value.


Option variable: maxpsifracdenom

     Default value: 6

Let <x> be a rational number less than one of the form p/q'.  If
q' is greater than maxpsifracdenom', then psi[<n>](<x>)' will
not try to return a simplified value.


Function: makefact (<expr>)

     Transforms instances of binomial, gamma, and beta functions in
<expr> into factorials.


Function: numfactor (<expr>)

     Returns the numerical factor multiplying the expression <expr>,
which should be a single term.

content' returns the greatest common divisor (gcd) of all terms
in a sum.

(%i1) gamma (7/2);
15 sqrt(%pi)
(%o1)                     ------------
8
(%i2) numfactor (%);
15
(%o2)                          --
8



## 15.5 Exponential Integrals

The Exponential Integral and related funtions are defined in Abramowitz
and Stegun, Handbook of Mathematical Functions, Chapter 5

Function: expintegral_e1 (<z>)

     The Exponential Integral E1(z) (A&S 5.1.1)


Function: expintegral_ei (<z>)

     The Exponential Integral Ei(z) (A&S 5.1.2)


Function: expintegral_li (<z>)

     The Exponential Integral Li(z)  (A&S 5.1.3)


Function: expintegral_e (<n>,<z>)

     The Exponential Integral En(z)  (A&S 5.1.4)


Function: expintegral_si (<z>)

     The Exponential Integral Si(z) (A&S 5.2.1)


Function: expintegral_ci (<z>)

     The Exponential Integral Ci(z) (A&S 5.2.2)


Function: expintegral_shi (<z>)

     The Exponential Integral Shi(z) (A&S 5.2.3)


Function: expintegral_chi (<z>)

     The Exponential Integral Chi(z) (A&S 5.2.4)


Option variable: expintrep

     Default value: false

Change the representation of the Exponential Integral to
gamma_incomplete, expintegral_e1, expintegral_ei,
expintegral_li, expintegral_trig, expintegral_hyp


Option variable: expintexpand

     Default value: false

Expand the Exponential Integral E[n](z) for half integral values
in terms of Erfc or Erf and for positive integers in terms of Ei



## 15.6 Error Function

The Error function and related funtions are defined in Abramowitz and
Stegun, Handbook of Mathematical Functions, Chapter 7

Function: erf (<z>)

     The Error Function erf(z) (A&S 7.1.1)


Function: erfc (<z>)

     The Complementary Error Function erfc(z) (A&S 7.1.2)

erfc(z) = 1-erf(z)'


Function: erfi (<z>)

     The Imaginary Error Function.

erfi(z) = -%i*erf(%i*z)'


Function: erf_generalized (<z1>,<z2>)

     Generalized Error function Erf(z1,z2)


Function: fresnel_c (<z>)

     The Fresnel Integral C(z) = integrate(cos((%pi/2)*t^2),t,0,z).
(A&S 7.3.1)

The simplification fresnel_c(-x) = -fresnel_c(x) is applied when
flag trigsign' is true.

The simplification fresnel_c(%i*x) =  %i*fresnel_c(x) is applied
when flag %iargs' is true.

See flags erf_representation' and hypergeometric_representation'.


Function: fresnel_s (<z>)

     The Fresnel Integral S(z) = integrate(sin((%pi/2)*t^2),t,0,z).
(A&S 7.3.2)

The simplification fresnel_s(-x) = -fresnel_s(x) is applied when
flag trigsign' is true.

The simplification fresnel_s(%i*x) =  -%i*fresnel_s(x) is applied
when flag %iargs' is true.

See flags erf_representation' and hypergeometric_representation'.


Option variable: erf_representation

     Default value: false

When T erfc, erfi, erf_generalized, fresnel_s and fresnel_c are
transformed to erf.


Option variable: hypergeometric_representation

     Default value: false

Enables transformation to a Hypergeometric representation for
fresnel_s and fresnel_c



## 15.7 Struve Functions

The Struve functions are defined in Abramowitz and Stegun, Handbook of
Mathematical Functions, Chapter 12.

Function: struve_h (<v>, <z>)

     The Struve Function H of order v and argument z. (A&S 12.1.1)


Function: struve_l (<v>, <z>)

     The Modified Struve Function L of order v and argument z. (A&S
12.2.1)



## 15.8 Hypergeometric Functions

The Hypergeometric Functions are defined in Abramowitz and Stegun,
Handbook of Mathematical Functions, Chapters 13 and 15.

Maxima has very limited knowledge of these functions.  They can be
returned from function hgfred'.

Function: %m [<k>,<u>] (<z>)

     Whittaker M function M[k,u](z) =
exp(-z/2)*z^(1/2+u)*M(1/2+u-k,1+2*u,z)'.  (A&S 13.1.32)


Function: %w [<k>,<u>] (<z>)

     Whittaker W function.  (A&S 13.1.33)


Function: %f [<p>,<q>] (<[a],[b],z>)

     The pFq(a1,a2,..ap;b1,b2,..bq;z) hypergeometric function, where
a' a list of length p' and b' a list of length q'.


Function: hypergeometric ([<a1>, ..., <ap>],[<b1>, ... ,<bq>], x)

     The hypergeometric function. Unlike Maxima's %f' hypergeometric
function, the function hypergeometric' is a simplifying function;
also, hypergeometric' supports complex double and big floating
point evaluation. For the Gauss hypergeometric function, that is p
= 2 and q = 1, floating point evaluation outside the unit circle
is supported, but in general, it is not supported.

When the option variable expand_hypergeometric' is true (default
is false) and one of the arguments a1' through ap' is a negative
integer (a polynomial case), hypergeometric' returns an expanded
polynomial.

Examples:

(%i1)  hypergeometric([],[],x);
(%o1) %e^x

Polynomial cases automatically expand when expand_hypergeometric'
is true:

(%i2) hypergeometric([-3],,x);
(%o2) hypergeometric([-3],,x)

(%i3) hypergeometric([-3],,x), expand_hypergeometric : true;
(%o3) -x^3/504+3*x^2/56-3*x/7+1

Both double float and big float evaluation is supported:

(%i4) hypergeometric([5.1],[7.1 + %i],0.42);
(%o4)       1.346250786375334 - 0.0559061414208204 %i
(%i5) hypergeometric([5,6],, 5.7 - %i);
(%o5)     .007375824009774946 - .001049813688578674 %i
(%i6) hypergeometric([5,6],, 5.7b0 - %i), fpprec : 30;
(%o6) 7.37582400977494674506442010824b-3
- 1.04981368857867315858055393376b-3 %i



## 15.9 Parabolic Cylinder Functions

The Parabolic Cylinder Functions are defined in Abramowitz and Stegun,
Handbook of Mathematical Functions, Chapter 19.

Maxima has very limited knowledge of these functions.  They can be
returned from function hgfred'.

Function: parabolic_cylinder_d (<v>, <z>)

     The parabolic cylinder function parabolic_cylinder_d(v,z)'. (A&S
19.3.1)



## 15.10 Functions and Variables for Special Functions

Function: specint (exp(- s*<t>) * <expr>, <t>)

     Compute the Laplace transform of <expr> with respect to the
variable <t>.  The integrand <expr> may contain special functions.

The following special functions are handled by specint':
incomplete gamma function, error functions (but not the error
function erfi', it is easy to transform erfi' e.g. to the error
function erf'), exponential integrals, bessel functions
(including products of bessel functions), hankel functions,
hermite and the laguerre polynomials.

Furthermore, specint' can handle the hypergeometric function
%f[p,q]([],[],z)', the whittaker function of the first kind
%m[u,k](z)' and of the second kind %w[u,k](z)'.

The result may be in terms of special functions and can include
unsimplified hypergeometric functions.

When laplace' fails to find a Laplace transform, specint' is
called.  Because laplace' knows more general rules for Laplace
transforms, it is preferable to use laplace' and not specint'.

demo(hypgeo)' displays several examples of Laplace transforms
computed by specint'.

Examples:
(%i1) assume (p > 0, a > 0)$(%i2) specint (t^(1/2) * exp(-a*t/4) * exp(-p*t), t); sqrt(%pi) (%o2) ------------ a 3/2 2 (p + -) 4 (%i3) specint (t^(1/2) * bessel_j(1, 2 * a^(1/2) * t^(1/2)) * exp(-p*t), t); - a/p sqrt(a) %e (%o3) --------------- 2 p Examples for exponential integrals: (%i4) assume(s>0,a>0,s-a>0)$
(%i5) ratsimp(specint(%e^(a*t)
*(log(a)+expintegral_e1(a*t))*%e^(-s*t),t));
log(s)
(%o5)                        ------
s - a
(%i6) logarc:true$(%i7) gamma_expand:true$

-sin(t)*expintegral_ci(t))*%e^(-s*t),t));
log(s)
(%o8)                        ------
2
s  + 1
ratsimp(specint((2*t*log(a)+2/a*sin(a*t)
-2*t*expintegral_ci(a*t))*%e^(-s*t),t));
2    2
log(s  + a )
(%o9)                     ------------
2
s

Results when using the expansion of gamma_incomplete' and when
changing the representation to expintegral_e1':

(%i10) assume(s>0)$(%i11) specint(1/sqrt(%pi*t)*unit_step(t-k)*%e^(-s*t),t); 1 gamma_incomplete(-, k s) 2 (%o11) ------------------------ sqrt(%pi) sqrt(s) (%i12) gamma_expand:true$
(%i13) specint(1/sqrt(%pi*t)*unit_step(t-k)*%e^(-s*t),t);
erfc(sqrt(k) sqrt(s))
(%o13)                        ---------------------
sqrt(s)

(%i14) expintrep:expintegral_e1$(%i15) ratsimp(specint(1/(t+a)^2*%e^(-s*t),t)); a s a s %e expintegral_e1(a s) - 1 (%o15) - --------------------------------- a  Function: hgfred (<a>, <b>, <t>)   Simplify the generalized hypergeometric function in terms of other, simpler, forms. <a> is a list of numerator parameters and <b> is a list of the denominator parameters. If hgfred' cannot simplify the hypergeometric function, it returns an expression of the form %f[p,q]([a], [b], x)' where <p> is the number of elements in <a>, and <q> is the number of elements in <b>. This is the usual pFq' generalized hypergeometric function. (%i1) assume(not(equal(z,0))); (%o1) [notequal(z, 0)] (%i2) hgfred([v+1/2],[2*v+1],2*%i*z); v/2 %i z 4 bessel_j(v, z) gamma(v + 1) %e (%o2) --------------------------------------- v z (%i3) hgfred([1,1],,z); log(1 - z) (%o3) - ---------- z (%i4) hgfred([a,a+1/2],[3/2],z^2); 1 - 2 a 1 - 2 a (z + 1) - (1 - z) (%o4) ------------------------------- 2 (1 - 2 a) z It can be beneficial to load orthopoly too as the following example shows. Note that <L> is the generalized Laguerre polynomial. (%i5) load(orthopoly)$
(%i6) hgfred([-2],[a],z);

(a - 1)
2 L       (z)
2
(%o6)                            -------------
a (a + 1)
(%i7) ev(%);

2
z        2 z
(%o7)                         --------- - --- + 1
a (a + 1)    a


Function: lambert_w (<z>)

     The principal branch of Lambert's W function W(z), the solution of
z = W(z) * exp(W(z))'.  (DLMF 4.13)


Function: generalized_lambert_w (<k>, <z>)

     The <k>-th branch of Lambert's W function W(z), the solution of z
= W(z) * exp(W(z))'. (DLMF 4.13)

The principal branch, denoted Wp(z) in DLMF, is lambert_w(z) =
generalized_lambert_w(0,z)'.

The other branch with real values, denoted Wm(z) in DLMF, is
generalized_lambert_w(-1,z)'.


Function: nzeta (<z>)

     The Plasma Dispersion Function nzeta(z) =
%i*sqrt(%pi)*exp(-z^2)*(1-erf(-%i*z))'


Function: nzetar (<z>)

     Returns realpart(nzeta(z))'.


Function: nzetai (<z>)

     Returns imagpart(nzeta(z))'.



## 16 Elliptic Functions


Introduction to Elliptic Functions and Integrals
Functions and Variables for Elliptic Functions
Functions and Variables for Elliptic Integrals


## 16.1 Introduction to Elliptic Functions and Integrals

Maxima includes support for Jacobian elliptic functions and for
complete and incomplete elliptic integrals.  This includes symbolic
manipulation of these functions and numerical evaluation as well.
Definitions of these functions and many of their properties can by
found in Abramowitz and Stegun, Chapter 16-17.  As much as possible, we
use the definitions and relationships given there.

In particular, all elliptic functions and integrals use the parameter
m instead of the modulus k or the modular angle \alpha.  This is one
area where we differ from Abramowitz and Stegun who use the modular
angle for the elliptic functions.  The following relationships are true:
m = k^2 and k = \sin(\alpha)

The elliptic functions and integrals are primarily intended to
support symbolic computation.  Therefore, most of derivatives of the
functions and integrals are known.  However, if floating-point values
are given, a floating-point result is returned.

Support for most of the other properties of elliptic functions and
integrals other than derivatives has not yet been written.

Some examples of elliptic functions:
(%i1) jacobi_sn (u, m);
(%o1)                    jacobi_sn(u, m)
(%i2) jacobi_sn (u, 1);
(%o2)                        tanh(u)
(%i3) jacobi_sn (u, 0);
(%o3)                        sin(u)
(%i4) diff (jacobi_sn (u, m), u);
(%o4)            jacobi_cn(u, m) jacobi_dn(u, m)
(%i5) diff (jacobi_sn (u, m), m);
(%o5) jacobi_cn(u, m) jacobi_dn(u, m)

elliptic_e(asin(jacobi_sn(u, m)), m)
(u - ------------------------------------)/(2 m)
1 - m

2
jacobi_cn (u, m) jacobi_sn(u, m)
+ --------------------------------
2 (1 - m)

Some examples of elliptic integrals:
(%i1) elliptic_f (phi, m);
(%o1)                  elliptic_f(phi, m)
(%i2) elliptic_f (phi, 0);
(%o2)                          phi
(%i3) elliptic_f (phi, 1);
phi   %pi
(%o3)                  log(tan(--- + ---))
2     4
(%i4) elliptic_e (phi, 1);
(%o4)                       sin(phi)
(%i5) elliptic_e (phi, 0);
(%o5)                          phi
(%i6) elliptic_kc (1/2);
1
(%o6)                    elliptic_kc(-)
2
(%i7) makegamma (%);
2 1
gamma (-)
4
(%o7)                      -----------
4 sqrt(%pi)
(%i8) diff (elliptic_f (phi, m), phi);
1
(%o8)                 ---------------------
2
sqrt(1 - m sin (phi))
(%i9) diff (elliptic_f (phi, m), m);
elliptic_e(phi, m) - (1 - m) elliptic_f(phi, m)
(%o9) (-----------------------------------------------
m

cos(phi) sin(phi)
- ---------------------)/(2 (1 - m))
2
sqrt(1 - m sin (phi))

Support for elliptic functions and integrals was written by Raymond
Toy.  It is placed under the terms of the General Public License (GPL)
that governs the distribution of Maxima.


## 16.2 Functions and Variables for Elliptic Functions

Function: jacobi_sn (<u>, <m>)

     The Jacobian elliptic function sn(u,m).


Function: jacobi_cn (<u>, <m>)

     The Jacobian elliptic function cn(u,m).


Function: jacobi_dn (<u>, <m>)

     The Jacobian elliptic function dn(u,m).


Function: jacobi_ns (<u>, <m>)

     The Jacobian elliptic function ns(u,m) = 1/sn(u,m).


Function: jacobi_sc (<u>, <m>)

     The Jacobian elliptic function sc(u,m) = sn(u,m)/cn(u,m).


Function: jacobi_sd (<u>, <m>)

     The Jacobian elliptic function sd(u,m) = sn(u,m)/dn(u,m).


Function: jacobi_nc (<u>, <m>)

     The Jacobian elliptic function nc(u,m) = 1/cn(u,m).


Function: jacobi_cs (<u>, <m>)

     The Jacobian elliptic function cs(u,m) = cn(u,m)/sn(u,m).


Function: jacobi_cd (<u>, <m>)

     The Jacobian elliptic function cd(u,m) = cn(u,m)/dn(u,m).


Function: jacobi_nd (<u>, <m>)

     The Jacobian elliptic function nd(u,m) = 1/dn(u,m).


Function: jacobi_ds (<u>, <m>)

     The Jacobian elliptic function ds(u,m) = dn(u,m)/sn(u,m).


Function: jacobi_dc (<u>, <m>)

     The Jacobian elliptic function dc(u,m) = dn(u,m)/cn(u,m).


Function: inverse_jacobi_sn (<u>, <m>)

     The inverse of the Jacobian elliptic function sn(u,m).


Function: inverse_jacobi_cn (<u>, <m>)

     The inverse of the Jacobian elliptic function cn(u,m).


Function: inverse_jacobi_dn (<u>, <m>)

     The inverse of the Jacobian elliptic function dn(u,m).


Function: inverse_jacobi_ns (<u>, <m>)

     The inverse of the Jacobian elliptic function ns(u,m).


Function: inverse_jacobi_sc (<u>, <m>)

     The inverse of the Jacobian elliptic function sc(u,m).


Function: inverse_jacobi_sd (<u>, <m>)

     The inverse of the Jacobian elliptic function sd(u,m).


Function: inverse_jacobi_nc (<u>, <m>)

     The inverse of the Jacobian elliptic function nc(u,m).


Function: inverse_jacobi_cs (<u>, <m>)

     The inverse of the Jacobian elliptic function cs(u,m).


Function: inverse_jacobi_cd (<u>, <m>)

     The inverse of the Jacobian elliptic function cd(u,m).


Function: inverse_jacobi_nd (<u>, <m>)

     The inverse of the Jacobian elliptic function nd(u,m).


Function: inverse_jacobi_ds (<u>, <m>)

     The inverse of the Jacobian elliptic function ds(u,m).


Function: inverse_jacobi_dc (<u>, <m>)

     The inverse of the Jacobian elliptic function dc(u,m).



## 16.3 Functions and Variables for Elliptic Integrals

Function: elliptic_f (<phi>, <m>)

     The incomplete elliptic integral of the first kind, defined as

integrate(1/sqrt(1 - m*sin(x)^2), x, 0, phi)


Function: elliptic_e (<phi>, <m>)

     The incomplete elliptic integral of the second kind, defined as

elliptic_e(phi, m) = integrate(sqrt(1 - m*sin(x)^2), x, 0, phi)


Function: elliptic_eu (<u>, <m>)

     The incomplete elliptic integral of the second kind, defined as

integrate(dn(v,m)^2,v,0,u) = integrate(sqrt(1-m*t^2)/sqrt(1-t^2),
t, 0, tau)

where tau = sn(u,m).

This is related to elliptic_e by

elliptic_eu(u, m) = elliptic_e(asin(sn(u,m)),m)


Function: elliptic_pi (<n>, <phi>, <m>)

     The incomplete elliptic integral of the third kind, defined as

integrate(1/(1-n*sin(x)^2)/sqrt(1 - m*sin(x)^2), x, 0, phi)

Only the derivative with respect to phi is known by Maxima.


Function: elliptic_kc (<m>)

     The complete elliptic integral of the first kind, defined as

integrate(1/sqrt(1 - m*sin(x)^2), x, 0, %pi/2)

For certain values of m, the value of the integral is known in
terms of Gamma functions.  Use makegamma' to evaluate them.


Function: elliptic_ec (<m>)

     The complete elliptic integral of the second kind, defined as

integrate(sqrt(1 - m*sin(x)^2), x, 0, %pi/2)

For certain values of m, the value of the integral is known in
terms of Gamma functions.  Use makegamma' to evaluate them.



## 17 Limits


Functions and Variables for Limits


## 17.1 Functions and Variables for Limits

Option variable: lhospitallim

     Default value: 4

lhospitallim' is the maximum number of times L'Hospital's rule is
used in limit'.  This prevents infinite looping in cases like
limit (cot(x)/csc(x), x, 0)'.


Function: limit

          limit (<expr>, <x>, <val>, <dir>)
limit (<expr>, <x>, <val>)
limit (<expr>)
Computes the limit of <expr> as the real variable <x> approaches
the value <val> from the direction <dir>.  <dir> may have the value
plus' for a limit from above, minus' for a limit from below, or
may be omitted (implying a two-sided limit is to be computed).

limit' uses the following special symbols: inf' (positive
infinity) and minf' (negative infinity).  On output it may also
use und' (undefined), ind' (indefinite but bounded) and
infinity' (complex infinity).

infinity' (complex infinity) is returned when the limit of the
absolute value of the expression is positive infinity, but the
limit of the expression itself is not positive infinity or
negative infinity.  This includes cases where the limit of the
complex argument is a constant, as in limit(log(x), x, minf)',
cases where the complex argument oscillates, as in limit((-2)^x,
x, inf)', and cases where the complex argument is different for
either side of a two-sided limit, as in limit(1/x, x, 0)' and
limit(log(x), x, 0)'.

lhospitallim' is the maximum number of times L'Hospital's rule is
used in limit'.  This prevents infinite looping in cases like
limit (cot(x)/csc(x), x, 0)'.

tlimswitch' when true will allow the limit' command to use
Taylor series expansion when necessary.

limsubst' prevents limit' from attempting substitutions on
unknown forms.  This is to avoid bugs like limit (f(n)/f(n+1), n,
inf)' giving 1.  Setting limsubst' to true' will allow such
substitutions.

limit' with one argument is often called upon to simplify constant
expressions, for example, limit (inf-1)'.

example (limit)' displays some examples.

For the method see Wang, P., "Evaluation of Definite Integrals by
Symbolic Manipulation", Ph.D. thesis, MAC TR-92, October 1971.


Option variable: limsubst

     Default value: false'

prevents limit' from attempting substitutions on unknown forms.
This is to avoid bugs like limit (f(n)/f(n+1), n, inf)' giving 1.
Setting limsubst' to true' will allow such substitutions.


Function: tlimit

          tlimit (<expr>, <x>, <val>, <dir>)
tlimit (<expr>, <x>, <val>)
tlimit (<expr>)
Take the limit of the Taylor series expansion of expr' in x' at
val' from direction dir'.


Option variable: tlimswitch

     Default value: true'

When tlimswitch' is true', the limit' command will use a Taylor
series expansion if the limit of the input expression cannot be
computed directly.  This allows evaluation of limits such as
limit(x/(x-1)-1/log(x),x,1,plus)'.  When tlimswitch' is false'
and the limit of input expression cannot be computed directly,
limit' will return an unevaluated limit expression.



## 18 Differentiation


Functions and Variables for Differentiation


## 18.1 Functions and Variables for Differentiation

Function: antid (<expr>, <x>, <u(x)>)

     Returns a two-element list, such that an antiderivative of <expr>
with respect to <x> can be constructed from the list.  The
expression <expr> may contain an unknown function <u> and its
derivatives.

Let <L>, a list of two elements, be the return value of antid'.
Then <L> + 'integrate (<L>, <x>)' is an antiderivative of
<expr> with respect to <x>.

When antid' succeeds entirely, the second element of the return
value is zero.  Otherwise, the second element is nonzero, and the
first element is nonzero or zero.  If antid' cannot make any
progress, the first element is zero and the second nonzero.

load ("antid")' loads this function.  The antid' package also
defines the functions nonzeroandfreeof' and linear'.

antid' is related to antidiff' as follows.  Let <L>, a list of
two elements, be the return value of antid'.  Then the return
value of antidiff' is equal to <L> + 'integrate (<L>,
<x>)' where <x> is the variable of integration.

Examples:

(%i1) load ("antid")$(%i2) expr: exp (z(x)) * diff (z(x), x) * y(x); z(x) d (%o2) y(x) %e (-- (z(x))) dx (%i3) a1: antid (expr, x, z(x)); z(x) z(x) d (%o3) [y(x) %e , - %e (-- (y(x)))] dx (%i4) a2: antidiff (expr, x, z(x)); / z(x) [ z(x) d (%o4) y(x) %e - I %e (-- (y(x))) dx ] dx / (%i5) a2 - (first (a1) + 'integrate (second (a1), x)); (%o5) 0 (%i6) antid (expr, x, y(x)); z(x) d (%o6) [0, y(x) %e (-- (z(x)))] dx (%i7) antidiff (expr, x, y(x)); / [ z(x) d (%o7) I y(x) %e (-- (z(x))) dx ] dx /  Function: antidiff (<expr>, <x>, <u>(<x>))   Returns an antiderivative of <expr> with respect to <x>. The expression <expr> may contain an unknown function <u> and its derivatives. When antidiff' succeeds entirely, the resulting expression is free of integral signs (that is, free of the integrate' noun). Otherwise, antidiff' returns an expression which is partly or entirely within an integral sign. If antidiff' cannot make any progress, the return value is entirely within an integral sign. load ("antid")' loads this function. The antid' package also defines the functions nonzeroandfreeof' and linear'. antidiff' is related to antid' as follows. Let <L>, a list of two elements, be the return value of antid'. Then the return value of antidiff' is equal to <L> + 'integrate (<L>, <x>)' where <x> is the variable of integration. Examples: (%i1) load ("antid")$
(%i2) expr: exp (z(x)) * diff (z(x), x) * y(x);
z(x)  d
(%o2)                y(x) %e     (-- (z(x)))
dx
(%i3) a1: antid (expr, x, z(x));
z(x)      z(x)  d
(%o3)          [y(x) %e    , - %e     (-- (y(x)))]
dx
(%i4) a2: antidiff (expr, x, z(x));
/
z(x)   [   z(x)  d
(%o4)         y(x) %e     - I %e     (-- (y(x))) dx
]         dx
/
(%i5) a2 - (first (a1) + 'integrate (second (a1), x));
(%o5)                           0
(%i6) antid (expr, x, y(x));
z(x)  d
(%o6)             [0, y(x) %e     (-- (z(x)))]
dx
(%i7) antidiff (expr, x, y(x));
/
[        z(x)  d
(%o7)             I y(x) %e     (-- (z(x))) dx
]              dx
/


Function: at

          at (<expr>, [<eqn_1>, ..., <eqn_n>])
at (<expr>, <eqn>)
Evaluates the expression <expr> with the variables assuming the
values as specified for them in the list of equations [<eqn_1>,
..., <eqn_n>]' or the single equation <eqn>.

If a subexpression depends on any of the variables for which a
value is specified but there is no atvalue' specified and it
can't be otherwise evaluated, then a noun form of the at' is
returned which displays in a two-dimensional form.

at' carries out multiple substitutions in parallel.

substitutions, see also subst' and ev'.

Examples:

(%i1) atvalue (f(x,y), [x = 0, y = 1], a^2);
2
(%o1)                          a
(%i2) atvalue ('diff (f(x,y), x), x = 0, 1 + y);
(%o2)                        @2 + 1
(%i3) printprops (all, atvalue);
!
d             !
--- (f(@1, @2))!       = @2 + 1
d@1            !
!@1 = 0

2
f(0, 1) = a

(%o3)                         done
(%i4) diff (4*f(x, y)^2 - u(x, y)^2, x);
d                          d
(%o4)  8 f(x, y) (-- (f(x, y))) - 2 u(x, y) (-- (u(x, y)))
dx                         dx
(%i5) at (%, [x = 0, y = 1]);
!
2              d           !
(%o5)     16 a  - 2 u(0, 1) (-- (u(x, y))!            )
dx          !
!x = 0, y = 1


Property: atomgrad

     atomgrad' is the atomic gradient property of an expression.  This


Function: atvalue

          atvalue (<expr>, [<x_1> = <a_1>, ..., <x_m> = <a_m>], <c>)
atvalue (<expr>, <x_1> = <a_1>, <c>)
Assigns the value <c> to <expr> at the point <x> = <a>'.
Typically boundary values are established by this mechanism.

<expr> is a function evaluation, <f>(<x_1>, ..., <x_m>)', or a
derivative, diff (<f>(<x_1>, ..., <x_m>), <x_1>, <n_1>, ...,
<x_n>, <n_m>)' in which the function arguments explicitly appear.
<n_i> is the order of differentiation with respect to <x_i>.

The point at which the atvalue is established is given by the list
of equations [<x_1> = <a_1>, ..., <x_m> = <a_m>]'.  If there is a
single variable <x_1>, the sole equation may be given without
enclosing it in a list.

printprops ([<f_1>, <f_2>, ...], atvalue)' displays the atvalues
of the functions <f_1>, <f_2>, ...' as specified by calls to
atvalue'.  printprops (<f>, atvalue)' displays the atvalues of
one function <f>.  printprops (all, atvalue)' displays the
atvalues of all functions for which atvalues are defined.

The symbols @1', @2', ... represent the variables <x_1>, <x_2>,
... when atvalues are displayed.

atvalue' evaluates its arguments.  atvalue' returns <c>, the
atvalue.

Examples:

(%i1) atvalue (f(x,y), [x = 0, y = 1], a^2);
2
(%o1)                          a
(%i2) atvalue ('diff (f(x,y), x), x = 0, 1 + y);
(%o2)                        @2 + 1
(%i3) printprops (all, atvalue);
!
d             !
--- (f(@1, @2))!       = @2 + 1
d@1            !
!@1 = 0

2
f(0, 1) = a

(%o3)                         done
(%i4) diff (4*f(x,y)^2 - u(x,y)^2, x);
d                          d
(%o4)  8 f(x, y) (-- (f(x, y))) - 2 u(x, y) (-- (u(x, y)))
dx                         dx
(%i5) at (%, [x = 0, y = 1]);
!
2              d           !
(%o5)     16 a  - 2 u(0, 1) (-- (u(x, y))!            )
dx          !
!x = 0, y = 1


Function: cartan

     The exterior calculus of differential forms is a basic tool of
differential geometry developed by Elie Cartan and has important
applications in the theory of partial differential equations.  The
cartan' package implements the functions ext_diff' and
lie_diff', along with the operators ~' (wedge product) and |'
(contraction of a form with a vector.)  Type demo (tensor)' to
see a brief description of these commands along with examples.

cartan' was implemented by F.B. Estabrook and H.D. Wahlquist.


Function: del (<x>)

     del (<x>)' represents the differential of the variable x.

diff' returns an expression containing del' if an independent
variable is not specified.  In this case, the return value is the
so-called "total differential".

Examples:

(%i1) diff (log (x));
del(x)
(%o1)                        ------
x
(%i2) diff (exp (x*y));
x y              x y
(%o2)            x %e    del(y) + y %e    del(x)
(%i3) diff (x*y*z);
(%o3)         x y del(z) + x z del(y) + y z del(x)


Function: delta (<t>)

     The Dirac Delta function.

Currently only laplace' knows about the delta' function.

Example:

(%i1) laplace (delta (t - a) * sin(b*t), t, s);
Is  a  positive, negative, or zero?

p;
- a s
(%o1)                   sin(a b) %e


System variable: dependencies

Function: dependencies (<f_1>, ..., <f_n>)

     The variable dependencies' is the list of atoms which have
functional dependencies, assigned by depends', the function
dependencies', or gradef'.  The dependencies' list is
cumulative: each call to depends', dependencies', or gradef'
appends additional items.  The default value of dependencies' is
[]'.

The function dependencies(<f_1>, ..., <f_n>)' appends <f_1>, ...,
<f_n>, to the dependencies' list, where <f_1>, ..., <f_n> are
expressions of the form <f>(<x_1>, ..., <x_m>)', and <x_1>, ...,
<x_m> are any number of arguments.

dependencies(<f>(<x_1>, ..., <x_m>))' is equivalent to
depends(<f>, [<x_1>, ..., <x_m>])'.

See also depends' and gradef'.

(%i1) dependencies;
(%o1)                          []
(%i2) depends (foo, [bar, baz]);
(%o2)                    [foo(bar, baz)]
(%i3) depends ([g, h], [a, b, c]);
(%o3)               [g(a, b, c), h(a, b, c)]
(%i4) dependencies;
(%o4)        [foo(bar, baz), g(a, b, c), h(a, b, c)]
(%i5) dependencies (quux (x, y), mumble (u));
(%o5)                [quux(x, y), mumble(u)]
(%i6) dependencies;
(%o6) [foo(bar, baz), g(a, b, c), h(a, b, c), quux(x, y),
mumble(u)]
(%i7) remove (quux, dependency);
(%o7)                         done
(%i8) dependencies;
(%o8)  [foo(bar, baz), g(a, b, c), h(a, b, c), mumble(u)]


Function: depends (<f_1>, <x_1>, ..., <f_n>, <x_n>)

     Declares functional dependencies among variables for the purpose
of computing derivatives.  In the absence of declared dependence,
diff (f, x)' yields zero.  If depends (f, x)' is declared, diff
(f, x)' yields a symbolic derivative (that is, a diff' noun).

Each argument <f_1>, <x_1>, etc., can be the name of a variable or
array, or a list of names.  Every element of <f_i> (perhaps just a
single element) is declared to depend on every element of <x_i>
(perhaps just a single element).  If some <f_i> is the name of an
array or contains the name of an array, all elements of the array
depend on <x_i>.

diff' recognizes indirect dependencies established by depends'
and applies the chain rule in these cases.

remove (<f>, dependency)' removes all dependencies declared for
<f>.

depends' returns a list of the dependencies established.  The
dependencies are appended to the global variable dependencies'.
depends' evaluates its arguments.

diff' is the only Maxima command which recognizes dependencies
established by depends'.  Other functions (integrate',
laplace', etc.)  only recognize dependencies explicitly
represented by their arguments.  For example, integrate' does not
recognize the dependence of f' on x' unless explicitly
represented as integrate (f(x), x)'.

depends(<f>, [<x_1>, ..., <x_n>])' is equivalent to
dependencies(<f>(<x_1>, ..., <x_n>))'.

(%i1) depends ([f, g], x);
(%o1)                     [f(x), g(x)]
(%i2) depends ([r, s], [u, v, w]);
(%o2)               [r(u, v, w), s(u, v, w)]
(%i3) depends (u, t);
(%o3)                        [u(t)]
(%i4) dependencies;
(%o4)      [f(x), g(x), r(u, v, w), s(u, v, w), u(t)]
(%i5) diff (r.s, u);
dr           ds
(%o5)                    -- . s + r . --
du           du

(%i6) diff (r.s, t);
dr du           ds du
(%o6)                 -- -- . s + r . -- --
du dt           du dt

(%i7) remove (r, dependency);
(%o7)                         done
(%i8) diff (r.s, t);
ds du
(%o8)                       r . -- --
du dt


Option variable: derivabbrev

     Default value: false'

When derivabbrev' is true', symbolic derivatives (that is,
diff' nouns) are displayed as subscripts.  Otherwise, derivatives
are displayed in the Leibniz notation dy/dx'.


Function: derivdegree (<expr>, <y>, <x>)

     Returns the highest degree of the derivative of the dependent
variable <y> with respect to the independent variable <x> occuring
in <expr>.

Example:

(%i1) 'diff (y, x, 2) + 'diff (y, z, 3) + 'diff (y, x) * x^2;
3     2
d y   d y    2 dy
(%o1)                   --- + --- + x  --
3     2      dx
dz    dx
(%i2) derivdegree (%, y, x);
(%o2)                           2


Function: derivlist (<var_1>, ..., <var_k>)

     Causes only differentiations with respect to the indicated
variables, within the ev' command.


Option variable: derivsubst

     Default value: false'

When derivsubst' is true', a non-syntactic substitution such as
subst (x, 'diff (y, t), 'diff (y, t, 2))' yields 'diff (x, t)'.


Function: diff

          diff (<expr>, <x_1>, <n_1>, ..., <x_m>, <n_m>)
diff (<expr>, <x>, <n>)
diff (<expr>, <x>)
diff (<expr>)
Returns the derivative or differential of <expr> with respect to
some or all variables in <expr>.

diff (<expr>, <x>, <n>)' returns the <n>'th derivative of <expr>
with respect to <x>.

diff (<expr>, <x_1>, <n_1>, ..., <x_m>, <n_m>)' returns the mixed
partial derivative of <expr> with respect to <x_1>, ..., <x_m>.
It is equivalent to diff (... (diff (<expr>, <x_m>, <n_m>) ...),
<x_1>, <n_1>)'.

diff (<expr>, <x>)' returns the first derivative of <expr> with
respect to the variable <x>.

diff (<expr>)' returns the total differential of <expr>, that is,
the sum of the derivatives of <expr> with respect to each its
variables times the differential del' of each variable.  No
further simplification of del' is offered.

The noun form of diff' is required in some contexts, such as
stating a differential equation.  In these cases, diff' may be
quoted (as 'diff') to yield the noun form instead of carrying out
the differentiation.

When derivabbrev' is true', derivatives are displayed as
subscripts.  Otherwise, derivatives are displayed in the Leibniz
notation, dy/dx'.

Examples:

(%i1) diff (exp (f(x)), x, 2);
2
f(x)  d               f(x)  d         2
(%o1)       %e     (--- (f(x))) + %e     (-- (f(x)))
2                   dx
dx
(%i2) derivabbrev: true$(%i3) 'integrate (f(x, y), y, g(x), h(x)); h(x) / [ (%o3) I f(x, y) dy ] / g(x) (%i4) diff (%, x); h(x) / [ (%o4) I f(x, y) dy + f(x, h(x)) h(x) - f(x, g(x)) g(x) ] x x x / g(x) For the tensor package, the following modifications have been incorporated: (1) The derivatives of any indexed objects in <expr> will have the variables <x_i> appended as additional arguments. Then all the derivative indices will be sorted. (2) The <x_i> may be integers from 1 up to the value of the variable dimension' [default value: 4]. This will cause the differentiation to be carried out with respect to the <x_i>'th member of the list coordinates' which should be set to a list of the names of the coordinates, e.g., [x, y, z, t]'. If coordinates' is bound to an atomic variable, then that variable subscripted by <x_i> will be used for the variable of differentiation. This permits an array of coordinate names or subscripted names like X', X', ... to be used. If coordinates' has not been assigned a value, then the variables will be treated as in (1) above.  Special symbol: diff   When diff' is present as an evflag' in call to ev', all differentiations indicated in expr' are carried out.  Function: dscalar (<f>)   Applies the scalar d'Alembertian to the scalar function <f>. load ("ctensor")' loads this function.  Function: express (<expr>)   Expands differential operator nouns into expressions in terms of partial derivatives. express' recognizes the operators grad', div', curl', laplacian'. express' also expands the cross product ~'. Symbolic derivatives (that is, diff' nouns) in the return value of express may be evaluated by including diff' in the ev' function call or command line. In this context, diff' acts as an evfun'. load ("vect")' loads this function. Examples: (%i1) load ("vect")$
(%i2) grad (x^2 + y^2 + z^2);
2    2    2
(%o2)                  grad (z  + y  + x )
(%i3) express (%);
d    2    2    2   d    2    2    2   d    2    2    2
(%o3) [-- (z  + y  + x ), -- (z  + y  + x ), -- (z  + y  + x )]
dx                 dy                 dz
(%i4) ev (%, diff);
(%o4)                    [2 x, 2 y, 2 z]
(%i5) div ([x^2, y^2, z^2]);
2   2   2
(%o5)                   div [x , y , z ]
(%i6) express (%);
d    2    d    2    d    2
(%o6)              -- (z ) + -- (y ) + -- (x )
dz        dy        dx
(%i7) ev (%, diff);
(%o7)                    2 z + 2 y + 2 x
(%i8) curl ([x^2, y^2, z^2]);
2   2   2
(%o8)                   curl [x , y , z ]
(%i9) express (%);
d    2    d    2   d    2    d    2   d    2    d    2
(%o9) [-- (z ) - -- (y ), -- (x ) - -- (z ), -- (y ) - -- (x )]
dy        dz       dz        dx       dx        dy
(%i10) ev (%, diff);
(%o10)                      [0, 0, 0]
(%i11) laplacian (x^2 * y^2 * z^2);
2  2  2
(%o11)                laplacian (x  y  z )
(%i12) express (%);
2                2                2
d     2  2  2    d     2  2  2    d     2  2  2
(%o12)  --- (x  y  z ) + --- (x  y  z ) + --- (x  y  z )
2                2                2
dz               dy               dx
(%i13) ev (%, diff);
2  2      2  2      2  2
(%o13)             2 y  z  + 2 x  z  + 2 x  y
(%i14) [a, b, c] ~ [x, y, z];
(%o14)                [a, b, c] ~ [x, y, z]
(%i15) express (%);
(%o15)          [b z - c y, c x - a z, a y - b x]


Function: gradef

          gradef (<f>(<x_1>, ..., <x_n>), <g_1>, ..., <g_m>)
Defines the partial derivatives (i.e., the components of the
gradient) of the function <f> or variable <a>.

gradef (<f>(<x_1>, ..., <x_n>), <g_1>, ..., <g_m>)' defines
d<f>/d<x_i>' as <g_i>, where <g_i> is an expression; <g_i> may be
a function call, but not the name of a function.  The number of
partial derivatives <m> may be less than the number of arguments
<n>, in which case derivatives are defined with respect to <x_1>
through <x_m> only.

gradef (<a>, <x>, <expr>)' defines the derivative of variable <a>
with respect to <x> as <expr>.  This also establishes the
dependence of <a> on <x> (via depends (<a>, <x>)').

The first argument <f>(<x_1>, ..., <x_n>)' or <a> is quoted, but
the remaining arguments <g_1>, ..., <g_m> are evaluated.  gradef'
returns the function or variable for which the partial derivatives
are defined.

gradef' can redefine the derivatives of Maxima's built-in
functions.  For example, gradef (sin(x), sqrt (1 - sin(x)^2))'
redefines the derivative of sin'.

gradef' cannot define partial derivatives for a subscripted
function.

printprops ([<f_1>, ..., <f_n>], gradef)' displays the partial
derivatives of the functions <f_1>, ..., <f_n>, as defined by
gradef'.

printprops ([<a_n>, ..., <a_n>], atomgrad)' displays the partial
derivatives of the variables <a_n>, ..., <a_n>, as defined by
gradef'.

gradefs' is the list of the functions for which partial
derivatives have been defined by gradef'.  gradefs' does not
include any variables for which partial derivatives have been
defined by gradef'.

Gradients are needed when, for example, a function is not known
explicitly but its first derivatives are and it is desired to
obtain higher order derivatives.


System variable: gradefs

     Default value: []'

gradefs' is the list of the functions for which partial
derivatives have been defined by gradef'.  gradefs' does not
include any variables for which partial derivatives have been


Function: laplace (<expr>, <t>, <s>)

     Attempts to compute the Laplace transform of <expr> with respect
to the variable <t> and transform parameter <s>.

laplace' recognizes in <expr> the functions delta', exp',
log', sin', cos', sinh', cosh', and erf', as well as
derivative', integrate', sum', and ilt'.  If laplace fails to
find a transform the function specint' is called.  specint' can
find the laplace transform for expressions with special functions
like the bessel functions bessel_j', bessel_i', ...  and can
handle the unit_step' function.  See also specint'.

If specint' cannot find a solution too, a noun laplace' is
returned.

<expr> may also be a linear, constant coefficient differential
equation in which case atvalue' of the dependent variable is used.
The required atvalue may be supplied either before or after the
transform is computed.  Since the initial conditions must be
specified at zero, if one has boundary conditions imposed
elsewhere he can impose these on the general solution and
eliminate the constants by solving the general solution for them
and substituting their values back.

laplace' recognizes convolution integrals of the form integrate
(f(x) * g(t - x), x, 0, t)'; other kinds of convolutions are not
recognized.

Functional relations must be explicitly represented in <expr>;
implicit relations, established by depends', are not recognized.
That is, if <f> depends on <x> and <y>, f (x, y)' must appear in
<expr>.

See also ilt', the inverse Laplace transform.

Examples:

(%i1) laplace (exp (2*t + a) * sin(t) * t, t, s);
a
%e  (2 s - 4)
(%o1)                    ---------------
2           2
(s  - 4 s + 5)
(%i2) laplace ('diff (f (x), x), x, s);
(%o2)             s laplace(f(x), x, s) - f(0)
(%i3) diff (diff (delta (t), t), t);
2
d
(%o3)                    --- (delta(t))
2
dt
(%i4) laplace (%, t, s);
!
d            !         2
(%o4)        - -- (delta(t))!      + s  - delta(0) s
dt           !
!t = 0
(%i5) assume(a>0)$(%i6) laplace(gamma_incomplete(a,t),t,s),gamma_expand:true; - a - 1 gamma(a) gamma(a) s (%o6) -------- - ----------------- s 1 a (- + 1) s (%i7) factor(laplace(gamma_incomplete(1/2,t),t,s)); s + 1 sqrt(%pi) (sqrt(s) sqrt(-----) - 1) s (%o7) ----------------------------------- 3/2 s + 1 s sqrt(-----) s (%i8) assume(exp(%pi*s)>1)$
(%i9) laplace(sum((-1)^n*unit_step(t-n*%pi)*sin(t),n,0,inf),t,s),
simpsum;
%i                         %i
------------------------ - ------------------------
- %pi s                    - %pi s
(s + %i) (1 - %e       )   (s - %i) (1 - %e       )
(%o9)         ---------------------------------------------------
2
(%i9) factor(%);
%pi s
%e
(%o9)                   -------------------------------
%pi s
(s - %i) (s + %i) (%e      - 1)



## 19 Integration


Introduction to Integration
Functions and Variables for Integration


## 19.1 Introduction to Integration

Maxima has several routines for handling integration.  The integrate'
function makes use of most of them.  There is also the antid' package,
which handles an unspecified function (and its derivatives, of course).
For numerical uses, there is a set of adaptive integrators from
QUADPACK, named quad_qag', quad_qags', etc., which are described
worked on, see specint' for details.  Generally speaking, Maxima only
handles integrals which are integrable in terms of the "elementary
functions" (rational functions, trigonometrics, logs, exponentials,
radicals, etc.) and a few extensions (error function, dilogarithm).  It
does not handle integrals in terms of unknown functions such as g(x)'
and h(x)'.


## 19.2 Functions and Variables for Integration

Function: changevar (<expr>, <f(x,y)>, <y>, <x>)

     Makes the change of variable given by <f(x,y)> = 0' in all
integrals occurring in <expr> with integration with respect to <x>.
The new variable is <y>.

(%i1) assume(a > 0)$(%i2) 'integrate (%e**sqrt(a*y), y, 0, 4); 4 / [ sqrt(a) sqrt(y) (%o2) I %e dy ] / 0 (%i3) changevar (%, y-z^2/a, z, y); 0 / [ abs(z) 2 I z %e dz ] / - 2 sqrt(a) (%o3) - ---------------------------- a An expression containing a noun form, such as the instances of 'integrate' above, may be evaluated by ev' with the nouns' flag. For example, the expression returned by changevar' above may be evaluated by ev (%o3, nouns)'. changevar' may also be used to changes in the indices of a sum or product. However, it must be realized that when a change is made in a sum or product, this change must be a shift, i.e., i = j+ ...', not a higher degree function. E.g., (%i4) sum (a[i]*x^(i-2), i, 0, inf); inf ==== \ i - 2 (%o4) > a x / i ==== i = 0 (%i5) changevar (%, i-2-n, n, i); inf ==== \ n (%o5) > a x / n + 2 ==== n = - 2  Function: dblint (<f>, <r>, <s>, <a>, <b>)   A double-integral routine which was written in top-level Maxima and then translated and compiled to machine code. Use load (dblint)' to access this package. It uses the Simpson's rule method in both the x and y directions to calculate /b /s(x) | | | | f(x,y) dy dx | | /a /r(x) The function <f> must be a translated or compiled function of two variables, and <r> and <s> must each be a translated or compiled function of one variable, while <a> and <b> must be floating point numbers. The routine has two global variables which determine the number of divisions of the x and y intervals: dblint_x' and dblint_y', both of which are initially 10, and can be changed independently to other integer values (there are 2*dblint_x+1' points computed in the x direction, and 2*dblint_y+1' in the y direction). The routine subdivides the X axis and then for each value of X it first computes <r>(x)' and <s>(x)'; then the Y axis between <r>(x)' and <s>(x)' is subdivided and the integral along the Y axis is performed using Simpson's rule; then the integral along the X axis is done using Simpson's rule with the function values being the Y-integrals. This procedure may be numerically unstable for a great variety of reasons, but is reasonably fast: avoid using it on highly oscillatory functions and functions with singularities (poles or branch points in the region). The Y integrals depend on how far apart <r>(x)' and <s>(x)' are, so if the distance <s>(x) - <r>(x)' varies rapidly with X, there may be substantial errors arising from truncation with different step-sizes in the various Y integrals. One can increase dblint_x' and dblint_y' in an effort to improve the coverage of the region, at the expense of computation time. The function values are not saved, so if the function is very time-consuming, you will have to wait for re-computation if you change anything (sorry). It is required that the functions <f>, <r>, and <s> be either translated or compiled prior to calling dblint'. This will result in orders of magnitude speed improvement over interpreted code in many cases! demo (dblint)' executes a demonstration of dblint' applied to an example problem.  Function: defint (<expr>, <x>, <a>, <b>)   Attempts to compute a definite integral. defint' is called by integrate' when limits of integration are specified, i.e., when integrate' is called as integrate (<expr>, <x>, <a>, <b>)'. Thus from the user's point of view, it is sufficient to call integrate'. defint' returns a symbolic expression, either the computed integral or the noun form of the integral. See quad_qag' and related functions for numerical approximation of definite integrals.  Option variable: erfflag   Default value: true' When erfflag' is false', prevents risch' from introducing the erf' function in the answer if there were none in the integrand to begin with.  Function: ilt (<expr>, <s>, <t>)   Computes the inverse Laplace transform of <expr> with respect to <s> and parameter <t>. <expr> must be a ratio of polynomials whose denominator has only linear and quadratic factors. By using the functions laplace' and ilt' together with the solve' or linsolve' functions the user can solve a single differential or convolution integral equation or a set of them. (%i1) 'integrate (sinh(a*x)*f(t-x), x, 0, t) + b*f(t) = t**2; t / [ 2 (%o1) I f(t - x) sinh(a x) dx + b f(t) = t ] / 0 (%i2) laplace (%, t, s); a laplace(f(t), t, s) 2 (%o2) b laplace(f(t), t, s) + --------------------- = -- 2 2 3 s - a s (%i3) linsolve ([%], ['laplace(f(t), t, s)]); 2 2 2 s - 2 a (%o3) [laplace(f(t), t, s) = --------------------] 5 2 3 b s + (a - a b) s (%i4) ilt (rhs (first (%)), s, t); Is a b (a b - 1) positive, negative, or zero? pos; sqrt(a b (a b - 1)) t 2 cosh(---------------------) 2 b a t (%o4) - ----------------------------- + ------- 3 2 2 a b - 1 a b - 2 a b + a 2 + ------------------ 3 2 2 a b - 2 a b + a  Option variable: intanalysis   Default value: true' When true', definite integration tries to find poles in the integrand in the interval of integration. If there are, then the integral is evaluated appropriately as a principal value integral. If intanalysis is false', this check is not performed and integration is done assuming there are no poles. See also ldefint'. Examples: Maxima can solve the following integrals, when intanalysis' is set to false': (%i1) integrate(1/(sqrt(x)+1),x,0,1); 1 / [ 1 (%o1) I ----------- dx ] sqrt(x) + 1 / 0 (%i2) integrate(1/(sqrt(x)+1),x,0,1),intanalysis:false; (%o2) 2 - 2 log(2) (%i3) integrate(cos(a)/sqrt((tan(a))^2 +1),a,-%pi/2,%pi/2); The number 1 isn't in the domain of atanh -- an error. To debug this try: debugmode(true); (%i4) intanalysis:false$
(%i5) integrate(cos(a)/sqrt((tan(a))^2+1),a,-%pi/2,%pi/2);
%pi
(%o5)                                 ---
2


Function: integrate

          integrate (<expr>, <x>)
integrate (<expr>, <x>, <a>, <b>)
Attempts to symbolically compute the integral of <expr> with
respect to <x>.  integrate (<expr>, <x>)' is an indefinite
integral, while integrate (<expr>, <x>, <a>, <b>)' is a definite
integral, with limits of integration <a> and <b>.  The limits
should not contain <x>, although integrate' does not enforce this
restriction.  <a> need not be less than <b>.  If <b> is equal to
<a>, integrate' returns zero.

See quad_qag' and related functions for numerical approximation of
definite integrals.  See residue' for computation of residues
(complex integration).  See antid' for an alternative means of
computing indefinite integrals.

The integral (an expression free of integrate') is returned if
integrate' succeeds.  Otherwise the return value is the noun form
of the integral (the quoted operator 'integrate') or an
expression containing one or more noun forms.  The noun form of
integrate' is displayed with an integral sign.

In some circumstances it is useful to construct a noun form by
hand, by quoting integrate' with a single quote, e.g.,
'integrate (<expr>, <x>)'.  For example, the integral may depend
on some parameters which are not yet computed.  The noun may be
applied to its arguments by ev (<i>, nouns)' where <i> is the
noun form of interest.

integrate' handles definite integrals separately from indefinite,
and employs a range of heuristics to handle each case.  Special
cases of definite integrals include limits of integration equal to
zero or infinity (inf' or minf'), trigonometric functions with
limits of integration equal to zero and %pi' or 2 %pi', rational
functions, integrals related to the definitions of the beta' and
psi' functions, and some logarithmic and trigonometric integrals.
Processing rational functions may include computation of residues.
If an applicable special case is not found, an attempt will be
made to compute the indefinite integral and evaluate it at the
limits of integration.  This may include taking a limit as a limit
ldefint'.

Special cases of indefinite integrals include trigonometric
functions, exponential and logarithmic functions, and rational
functions.  integrate' may also make use of a short table of
elementary integrals.

integrate' may carry out a change of variable if the integrand
has the form f(g(x)) * diff(g(x), x)'.  integrate' attempts to
find a subexpression g(x)' such that the derivative of g(x)'
divides the integrand.  This search may make use of derivatives
defined by the gradef' function.  See also changevar' and
antid'.

If none of the preceding heuristics find the indefinite integral,
the Risch algorithm is executed.  The flag risch' may be set as
an evflag', in a call to ev' or on the command line, e.g., ev
(integrate (<expr>, <x>), risch)' or integrate (<expr>, <x>),
risch'.  If risch' is present, integrate' calls the risch'

integrate' works only with functional relations represented
explicitly with the f(x)' notation.  integrate' does not respect
implicit dependencies established by the depends' function.

integrate' may need to know some property of a parameter in the
integrand.  integrate' will first consult the assume' database,
and, if the variable of interest is not there, integrate' will
ask the user.  Depending on the question, suitable responses are
yes;' or no;', or pos;', zero;', or neg;'.

integrate' is not, by default, declared to be linear.  See
declare' and linear'.

integrate' attempts integration by parts only in a few special
cases.

Examples:

* Elementary indefinite and definite integrals.

(%i1) integrate (sin(x)^3, x);
3
cos (x)
(%o1)                   ------- - cos(x)
3
(%i2) integrate (x/ sqrt (b^2 - x^2), x);
2    2
(%o2)                    - sqrt(b  - x )
(%i3) integrate (cos(x)^2 * exp(x), x, 0, %pi);
%pi
3 %e      3
(%o3)                      ------- - -
5      5
(%i4) integrate (x^2 * exp(-x^2), x, minf, inf);
sqrt(%pi)
(%o4)                       ---------
2

* Use of assume' and interactive query.

(%i1) assume (a > 1)$(%i2) integrate (x**a/(x+1)**(5/2), x, 0, inf); 2 a + 2 Is ------- an integer? 5 no; Is 2 a - 3 positive, negative, or zero? neg; 3 (%o2) beta(a + 1, - - a) 2 * Change of variable. There are two changes of variable in this example: one using a derivative established by gradef', and one using the derivation diff(r(x))' of an unspecified function r(x)'. (%i3) gradef (q(x), sin(x**2)); (%o3) q(x) (%i4) diff (log (q (r (x))), x); d 2 (-- (r(x))) sin(r (x)) dx (%o4) ---------------------- q(r(x)) (%i5) integrate (%, x); (%o5) log(q(r(x))) * Return value contains the 'integrate' noun form. In this example, Maxima can extract one factor of the denominator of a rational function, but cannot factor the remainder or otherwise find its integral. grind' shows the noun form 'integrate' in the result. See also integrate_use_rootsof' for more on integrals of rational functions. (%i1) expand ((x-4) * (x^3+2*x+1)); 4 3 2 (%o1) x - 4 x + 2 x - 7 x - 4 (%i2) integrate (1/%, x); / 2 [ x + 4 x + 18 I ------------- dx ] 3 log(x - 4) / x + 2 x + 1 (%o2) ---------- - ------------------ 73 73 (%i3) grind (%); log(x-4)/73-('integrate((x^2+4*x+18)/(x^3+2*x+1),x))/73$

* Defining a function in terms of an integral.  The body of a
function is not evaluated when the function is defined.  Thus
the body of f_1' in this example contains the noun form of
integrate'.  The quote-quote operator ''' causes the
integral to be evaluated, and the result becomes the body of
f_2'.

(%i1) f_1 (a) := integrate (x^3, x, 1, a);
3
(%o1)           f_1(a) := integrate(x , x, 1, a)
(%i2) ev (f_1 (7), nouns);
(%o2)                          600
(%i3) /* Note parentheses around integrate(...) here */
f_2 (a) := ''(integrate (x^3, x, 1, a));
4
a    1
(%o3)                   f_2(a) := -- - -
4    4
(%i4) f_2 (7);
(%o4)                          600


System variable: integration_constant

     Default value: %c'

When a constant of integration is introduced by indefinite
integration of an equation, the name of the constant is
constructed by concatenating integration_constant' and
integration_constant_counter'.

integration_constant' may be assigned any symbol.

Examples:

(%i1) integrate (x^2 = 1, x);
3
x
(%o1)                     -- = x + %c1
3
(%i2) integration_constant : 'k;
(%o2)                           k
(%i3) integrate (x^2 = 1, x);
3
x
(%o3)                      -- = x + k2
3


System variable: integration_constant_counter

     Default value: 0

When a constant of integration is introduced by indefinite
integration of an equation, the name of the constant is
constructed by concatenating integration_constant' and
integration_constant_counter'.

integration_constant_counter' is incremented before constructing
the next integration constant.

Examples:

(%i1) integrate (x^2 = 1, x);
3
x
(%o1)                     -- = x + %c1
3
(%i2) integrate (x^2 = 1, x);
3
x
(%o2)                     -- = x + %c2
3
(%i3) integrate (x^2 = 1, x);
3
x
(%o3)                     -- = x + %c3
3
(%i4) reset (integration_constant_counter);
(%o4)            [integration_constant_counter]
(%i5) integrate (x^2 = 1, x);
3
x
(%o5)                     -- = x + %c1
3


Option variable: integrate_use_rootsof

     Default value: false'

When integrate_use_rootsof' is true' and the denominator of a
rational function cannot be factored, integrate' returns the
integral in a form which is a sum over the roots (not yet known)
of the denominator.

For example, with integrate_use_rootsof' set to false',
integrate' returns an unsolved integral of a rational function in
noun form:

(%i1) integrate_use_rootsof: false$(%i2) integrate (1/(1+x+x^5), x); / 2 [ x - 4 x + 5 I ------------ dx 2 x + 1 ] 3 2 2 5 atan(-------) / x - x + 1 log(x + x + 1) sqrt(3) (%o2) ----------------- - --------------- + --------------- 7 14 7 sqrt(3) Now we set the flag to be true and the unsolved part of the integral will be expressed as a summation over the roots of the denominator of the rational function: (%i3) integrate_use_rootsof: true$
(%i4) integrate (1/(1+x+x^5), x);
====        2
\       (%r4  - 4 %r4 + 5) log(x - %r4)
>      -------------------------------
/                    2
====            3 %r4  - 2 %r4
3    2
%r4 in rootsof(x  - x  + 1)
(%o4) ----------------------------------------------------------
7

2 x + 1
2            5 atan(-------)
log(x  + x + 1)          sqrt(3)
- --------------- + ---------------
14             7 sqrt(3)

Alternatively the user may compute the roots of the denominator
separately, and then express the integrand in terms of these
roots, e.g., 1/((x - a)*(x - b)*(x - c))' or 1/((x^2 - (a+b)*x +
a*b)*(x - c))' if the denominator is a cubic polynomial.
Sometimes this will help Maxima obtain a more useful result.


Function: ldefint (<expr>, <x>, <a>, <b>)

     Attempts to compute the definite integral of <expr> by using
limit' to evaluate the indefinite integral of <expr> with respect
to <x> at the upper limit <b> and at the lower limit <a>.  If it
fails to compute the definite integral, ldefint' returns an
expression containing limits as noun forms.

ldefint' is not called from integrate', so executing ldefint
(<expr>, <x>, <a>, <b>)' may yield a different result than
integrate (<expr>, <x>, <a>, <b>)'.  ldefint' always uses the
same method to evaluate the definite integral, while integrate'
may employ various heuristics and may recognize some special cases.


Function: potential (<givengradient>)

     The calculation makes use of the global variable
potentialzeroloc' which must be nonlist' or of the form

[indeterminatej=expressionj, indeterminatek=expressionk, ...]

the former being equivalent to the nonlist expression for all
right-hand sides in the latter.  The indicated right-hand sides
are used as the lower limit of integration.  The success of the
integrations may depend upon their values and order.
potentialzeroloc' is initially set to 0.


Function: residue (<expr>, <z>, <z_0>)

     Computes the residue in the complex plane of the expression <expr>
when the variable <z> assumes the value <z_0>.  The residue is the
coefficient of (<z> - <z_0>)^(-1)' in the Laurent series for
<expr>.

(%i1) residue (s/(s**2+a**2), s, a*%i);
1
(%o1)                           -
2
(%i2) residue (sin(a*x)/x**4, x, 0);
3
a
(%o2)                         - --
6


Function: risch (<expr>, <x>)

     Integrates <expr> with respect to <x> using the transcendental
case of the Risch algorithm.  (The algebraic case of the Risch
algorithm has not been implemented.)  This currently handles the
cases of nested exponentials and logarithms which the main part of
integrate' can't do.  integrate' will automatically apply
risch' if given these cases.

erfflag', if false', prevents risch' from introducing the erf'
function in the answer if there were none in the integrand to begin
with.

(%i1) risch (x^2*erf(x), x);
2
3                      2                - x
%pi x  erf(x) + (sqrt(%pi) x  + sqrt(%pi)) %e
(%o1)   -------------------------------------------------
3 %pi
(%i2) diff(%, x), ratsimp;
2
(%o2)                       x  erf(x)


Function: tldefint (<expr>, <x>, <a>, <b>)

     Equivalent to ldefint' with tlimswitch' set to true'.



QUADPACK is a collection of functions for the numerical computation of
one-dimensional definite integrals.  It originated from a joint project
of R. Piessens (1), E. de Doncker (2), C. Ueberhuber (3), and D.
Kahaner (4).

The QUADPACK library included in Maxima is an automatic translation
(via the program f2cl') of the Fortran source code of QUADPACK as it
appears in the SLATEC Common Mathematical Library, Version 4.1 (5).
The SLATEC library is dated July 1993, but the QUADPACK functions were
written some years before.  There is another version of QUADPACK at
Netlib (6); it is not clear how that version differs from the SLATEC
version.

The QUADPACK functions included in Maxima are all automatic, in the
sense that these functions attempt to compute a result to a specified
accuracy, requiring an unspecified number of function evaluations.
Maxima's Lisp translation of QUADPACK also includes some non-automatic
functions, but they are not exposed at the Maxima level.

(7).


## 19.4 Functions and Variables for QUADPACK

Function: quad_qag

          quad_qag (<f(x)>, <x>, <a>, <b>, <key>, [<epsrel>, <epsabs>,
<limit>])
quad_qag (<f>, <x>, <a>, <b>, <key>, [<epsrel>, <epsabs>,
<limit>])
Integration of a general function over a finite interval.
quad_qag' implements a simple globally adaptive integrator using
the strategy of Aind (Piessens, 1973).  The caller may choose
among 6 pairs of Gauss-Kronrod quadrature formulae for the rule
evaluation component.  The high-degree rules are suitable for
strongly oscillating integrands.

integrate (f(x), x, a, b)

The function to be integrated is <f(x)>, with dependent variable
<x>, and the function is to be integrated between the limits <a>
and <b>.  <key> is the integrator to be used and should be an
integer between 1 and 6, inclusive.  The value of <key> selects
the order of the Gauss-Kronrod integration rule.  High-order rules
are suitable for strongly oscillating integrands.

The integrand may be specified as the name of a Maxima or Lisp
function or operator, a Maxima lambda expression, or a general
Maxima expression.

The numerical integration is done adaptively by subdividing the
integration region into sub-intervals until the desired accuracy is
achieved.

The keyword arguments are optional and may be specified in any
order.  They all take the form key=val'.  The keyword arguments
are:

epsrel'
Desired relative error of approximation.  Default is 1d-8.

epsabs'
Desired absolute error of approximation.  Default is 0.

limit'
Size of internal work array.  <limit> is the maximum number
of subintervals to use.  Default is 200.

quad_qag' returns a list of four elements:

* an approximation to the integral,

* the estimated absolute error of the approximation,

* the number integrand evaluations,

* an error code.

The error code (fourth element of the return value) can have the
values:

0'
if no problems were encountered;

1'
if too many sub-intervals were done;

2'
if excessive roundoff error is detected;

3'
if extremely bad integrand behavior occurs;

6'
if the input is invalid.


Function: quad_qags

          quad_qags (<f(x)>, <x>, <a>, <b>, [<epsrel>, <epsabs>,
<limit>])
quad_qags (<f>, <x>, <a>, <b>, [<epsrel>, <epsabs>, <limit>])
Integration of a general function over a finite interval.
quad_qags' implements globally adaptive interval subdivision with
extrapolation (de Doncker, 1978) by the Epsilon algorithm (Wynn,
1956).

integrate (f(x), x, a, b)

The function to be integrated is <f(x)>, with dependent variable
<x>, and the function is to be integrated between the limits <a>
and <b>.

The integrand may be specified as the name of a Maxima or Lisp
function or operator, a Maxima lambda expression, or a general
Maxima expression.

The keyword arguments are optional and may be specified in any
order.  They all take the form key=val'.  The keyword arguments
are:

epsrel'
Desired relative error of approximation.  Default is 1d-8.

epsabs'
Desired absolute error of approximation.  Default is 0.

limit'
Size of internal work array.  <limit> is the maximum number
of subintervals to use.  Default is 200.

quad_qags' returns a list of four elements:

* an approximation to the integral,

* the estimated absolute error of the approximation,

* the number integrand evaluations,

* an error code.

The error code (fourth element of the return value) can have the
values:

0'
no problems were encountered;

1'
too many sub-intervals were done;

2'
excessive roundoff error is detected;

3'

4'
failed to converge

5'
integral is probably divergent or slowly convergent

6'
if the input is invalid.

Examples:

(%i1) quad_qags (x^(1/2)*log(1/x), x, 0, 1, 'epsrel=1d-10);
(%o1)   [.4444444444444448, 1.11022302462516E-15, 315, 0]

Note that quad_qags' is more accurate and efficient than


Function: quad_qagi

          quad_qagi (<f(x)>, <x>, <a>, <b>, [<epsrel>, <epsabs>,
<limit>])
quad_qagi (<f>, <x>, <a>, <b>, [<epsrel>, <epsabs>, <limit>])
Integration of a general function over an infinite or
semi-infinite interval.  The interval is mapped onto a finite
interval and then the same strategy as in quad_qags' is applied.

quad_qagi' evaluates one of the following integrals

integrate (f(x), x, a, inf)

integrate (f(x), x, minf, a)

integrate (f(x), x, minf, inf)

using the Quadpack QAGI routine.  The function to be integrated is
<f(x)>, with dependent variable <x>, and the function is to be
integrated over an infinite range.

The integrand may be specified as the name of a Maxima or Lisp
function or operator, a Maxima lambda expression, or a general
Maxima expression.

One of the limits of integration must be infinity.  If not, then
quad_qagi' will just return the noun form.

The keyword arguments are optional and may be specified in any
order.  They all take the form key=val'.  The keyword arguments
are:

epsrel'
Desired relative error of approximation.  Default is 1d-8.

epsabs'
Desired absolute error of approximation.  Default is 0.

limit'
Size of internal work array.  <limit> is the maximum number
of subintervals to use.  Default is 200.

quad_qagi' returns a list of four elements:

* an approximation to the integral,

* the estimated absolute error of the approximation,

* the number integrand evaluations,

* an error code.

The error code (fourth element of the return value) can have the
values:

0'
no problems were encountered;

1'
too many sub-intervals were done;

2'
excessive roundoff error is detected;

3'

4'
failed to converge

5'
integral is probably divergent or slowly convergent

6'
if the input is invalid.


Function: quad_qawc

          quad_qawc (<f(x)>, <x>, <c>, <a>, <b>, [<epsrel>, <epsabs>,
<limit>])
quad_qawc (<f>, <x>, <c>, <a>, <b>, [<epsrel>, <epsabs>,
<limit>])
Computes the Cauchy principal value of f(x)/(x - c) over a finite
interval.  The strategy is globally adaptive, and modified
Clenshaw-Curtis integration is used on the subranges which contain
the point x = c.

quad_qawc' computes the Cauchy principal value of

integrate (f(x)/(x - c), x, a, b)

using the Quadpack QAWC routine.  The function to be integrated is
<f(x)>/(<x> - <c>)', with dependent variable <x>, and the
function is to be integrated over the interval <a> to <b>.

The integrand may be specified as the name of a Maxima or Lisp
function or operator, a Maxima lambda expression, or a general
Maxima expression.

The keyword arguments are optional and may be specified in any
order.  They all take the form key=val'.  The keyword arguments
are:

epsrel'
Desired relative error of approximation.  Default is 1d-8.

epsabs'
Desired absolute error of approximation.  Default is 0.

limit'
Size of internal work array.  <limit> is the maximum number
of subintervals to use.  Default is 200.

quad_qawc' returns a list of four elements:

* an approximation to the integral,

* the estimated absolute error of the approximation,

* the number integrand evaluations,

* an error code.

The error code (fourth element of the return value) can have the
values:

0'
no problems were encountered;

1'
too many sub-intervals were done;

2'
excessive roundoff error is detected;

3'

6'
if the input is invalid.


Function: quad_qawf

          quad_qawf (<f(x)>, <x>, <a>, <omega>, <trig>, [<epsabs>,
<limit>, <maxp1>, <limlst>])
quad_qawf (<f>, <x>, <a>, <omega>, <trig>, [<epsabs>,
<limit>, <maxp1>, <limlst>])
Calculates a Fourier cosine or Fourier sine transform on a
semi-infinite interval using the Quadpack QAWF function.  The same
approach as in quad_qawo' is applied on successive finite
intervals, and convergence acceleration by means of the Epsilon
algorithm (Wynn, 1956) is applied to the series of the integral
contributions.

quad_qawf' computes the integral

integrate (f(x)*w(x), x, a, inf)

The weight function w is selected by <trig>:

cos'
w(x) = cos (omega x)

sin'
w(x) = sin (omega x)

The integrand may be specified as the name of a Maxima or Lisp
function or operator, a Maxima lambda expression, or a general
Maxima expression.

The keyword arguments are optional and may be specified in any
order.  They all take the form key=val'.  The keyword arguments
are:

epsabs'
Desired absolute error of approximation.  Default is 1d-10.

limit'
Size of internal work array.  (<limit> - <limlst>)/2 is the
maximum number of subintervals to use.  Default is 200.

maxp1'
Maximum number of Chebyshev moments.  Must be greater than 0.
Default is 100.

limlst'
Upper bound on the number of cycles.  Must be greater than or
equal to 3.  Default is 10.

quad_qawf' returns a list of four elements:

* an approximation to the integral,

* the estimated absolute error of the approximation,

* the number integrand evaluations,

* an error code.

The error code (fourth element of the return value) can have the
values:

0'
no problems were encountered;

1'
too many sub-intervals were done;

2'
excessive roundoff error is detected;

3'

6'
if the input is invalid.


Function: quad_qawo

          quad_qawo (<f(x)>, <x>, <a>, <b>, <omega>, <trig>, [<epsrel>,
<epsabs>, <limit>, <maxp1>, <limlst>])
quad_qawo (<f>, <x>, <a>, <b>, <omega>, <trig>, [<epsrel>,
<epsabs>, <limit>, <maxp1>, <limlst>])
Integration of cos (omega x) f(x) or sin (omega x) f(x) over a
finite interval, where omega is a constant.  The rule evaluation
component is based on the modified Clenshaw-Curtis technique.
quad_qawo' applies adaptive subdivision with extrapolation,

quad_qawo' computes the integral using the Quadpack QAWO routine:

integrate (f(x)*w(x), x, a, b)

The weight function w is selected by <trig>:

cos'
w(x) = cos (omega x)

sin'
w(x) = sin (omega x)

The integrand may be specified as the name of a Maxima or Lisp
function or operator, a Maxima lambda expression, or a general
Maxima expression.

The keyword arguments are optional and may be specified in any
order.  They all take the form key=val'.  The keyword arguments
are:

epsrel'
Desired relative error of approximation.  Default is 1d-8.

epsabs'
Desired absolute error of approximation.  Default is 0.

limit'
Size of internal work array.  <limit>/2 is the maximum number
of subintervals to use.  Default is 200.

maxp1'
Maximum number of Chebyshev moments.  Must be greater than 0.
Default is 100.

limlst'
Upper bound on the number of cycles.  Must be greater than or
equal to 3.  Default is 10.

quad_qawo' returns a list of four elements:

* an approximation to the integral,

* the estimated absolute error of the approximation,

* the number integrand evaluations,

* an error code.

The error code (fourth element of the return value) can have the
values:

0'
no problems were encountered;

1'
too many sub-intervals were done;

2'
excessive roundoff error is detected;

3'

6'
if the input is invalid.


Function: quad_qaws

          quad_qaws (<f(x)>, <x>, <a>, <b>, <alpha>, <beta>, <wfun>,
[<epsrel>, <epsabs>, <limit>])
quad_qaws (<f>, <x>, <a>, <b>, <alpha>, <beta>, <wfun>,
[<epsrel>, <epsabs>, <limit>])
Integration of w(x) f(x) over a finite interval, where w(x) is a
certain algebraic or logarithmic function.  A globally adaptive
subdivision strategy is applied, with modified Clenshaw-Curtis
integration on the subintervals which contain the endpoints of the
interval of integration.

integrate (f(x)*w(x), x, a, b)

The weight function w is selected by <wfun>:

1'
w(x) = (x - a)^alpha (b - x)^beta

2'
w(x) = (x - a)^alpha (b - x)^beta log(x - a)

3'
w(x) = (x - a)^alpha (b - x)^beta log(b - x)

4'
w(x) = (x - a)^alpha (b - x)^beta log(x - a) log(b - x)

The integrand may be specified as the name of a Maxima or Lisp
function or operator, a Maxima lambda expression, or a general
Maxima expression.

The keyword arguments are optional and may be specified in any
order.  They all take the form key=val'.  The keyword arguments
are:

epsrel'
Desired relative error of approximation.  Default is 1d-8.

epsabs'
Desired absolute error of approximation.  Default is 0.

limit'
Size of internal work array.  <limit>is the maximum number of
subintervals to use.  Default is 200.

quad_qaws' returns a list of four elements:

* an approximation to the integral,

* the estimated absolute error of the approximation,

* the number integrand evaluations,

* an error code.

The error code (fourth element of the return value) can have the
values:

0'
no problems were encountered;

1'
too many sub-intervals were done;

2'
excessive roundoff error is detected;

3'

6'
if the input is invalid.


Function: quad_qagp

          quad_qagp (<f(x)>, <x>, <a>, <b>, <points>, [<epsrel>,
<epsabs>, <limit>])
quad_qagp (<f>, <x>, <a>, <b>, <points>, [<epsrel>, <epsabs>,
<limit>])
Integration of a general function over a finite interval.
quad_qagp' implements globally adaptive interval subdivision with
extrapolation (de Doncker, 1978) by the Epsilon algorithm (Wynn,
1956).

integrate (f(x), x, a, b)

The function to be integrated is <f(x)>, with dependent variable
<x>, and the function is to be integrated between the limits <a>
and <b>.

The integrand may be specified as the name of a Maxima or Lisp
function or operator, a Maxima lambda expression, or a general
Maxima expression.

To help the integrator, the user must supply a list of points where
the integrand is singular or discontinous.

The keyword arguments are optional and may be specified in any
order.  They all take the form key=val'.  The keyword arguments
are:

epsrel'
Desired relative error of approximation.  Default is 1d-8.

epsabs'
Desired absolute error of approximation.  Default is 0.

limit'
Size of internal work array.  <limit> is the maximum number
of subintervals to use.  Default is 200.

quad_qagp' returns a list of four elements:

* an approximation to the integral,

* the estimated absolute error of the approximation,

* the number integrand evaluations,

* an error code.

The error code (fourth element of the return value) can have the
values:

0'
no problems were encountered;

1'
too many sub-intervals were done;

2'
excessive roundoff error is detected;

3'

4'
failed to converge

5'
integral is probably divergent or slowly convergent

6'
if the input is invalid.

Examples:

(%o1)   [52.74074838347143, 2.6247632689546663e-7, 1029, 0]
(%o2)   [52.74074847951494, 4.088443219529836e-7, 1869, 0]

The integrand has singularities at 1' and sqrt(2)' so we supply
these points to quad_qagp'.  We also note that quad_qagp' is
more accurate and more efficient that quad_qags'.


Function: quad_control (<parameter>, [<value>])

     Control error handling for quadpack.  The parameter should be one
of the following symbols:

current_error'
The current error number

control'
Controls if messages are printed or not.  If it is set to
zero or less, messages are suppressed.

max_message'
The maximum number of times any message is to be printed.

If <value> is not given, then the current value of the <parameter>
is returned.  If <value> is given, the value of <parameter> is set
to the given value.



## 20 Equations


Functions and Variables for Equations


## 20.1 Functions and Variables for Equations

System variable: %rnum_list

     Default value: []'

%rnum_list' is the list of variables introduced in solutions by
solve' and algsys'.  %r' variables are added to %rnum_list' in
the order they are created.  This is convenient for doing
substitutions into the solution later on.  It's recommended to use
this list rather than doing concat ('%r, j)'.

(%i1) solve ([x + y = 3], [x,y]);
(%o1)              [[x = 3 - %r1, y = %r1]]
(%i2) %rnum_list;
(%o2)                       [%r1]
(%i3) sol : solve ([x + 2*y + 3*z = 4], [x,y,z]);
(%o3)   [[x = - 2 %r3 - 3 %r2 + 4, y = %r3, z = %r2]]
(%i4) %rnum_list;
(%o4)                     [%r2, %r3]
(%i5) for i : 1 thru length (%rnum_list) do
sol : subst (t[i], %rnum_list[i], sol)$(%i6) sol; (%o6) [[x = - 2 t - 3 t + 4, y = t , z = t ]] 2 1 2 1  Option variable: algepsilon   Default value: 10^8 algepsilon' is used by algsys'.  Option variable: algexact   Default value: false' algexact' affects the behavior of algsys' as follows: If algexact' is true', algsys' always calls solve' and then uses realroots' on solve''s failures. If algexact' is false', solve' is called only if the eliminant was not univariate, or if it was a quadratic or biquadratic. Thus algexact: true' does not guarantee only exact solutions, just that algsys' will first try as hard as it can to give exact solutions, and only yield approximations when all else fails.  Function: algsys   algsys ([<expr_1>, ..., <expr_m>], [<x_1>, ..., <x_n>]) algsys ([<eqn_1>, ..., <eqn_m>], [<x_1>, ..., <x_n>]) Solves the simultaneous polynomials <expr_1>, ..., <expr_m> or polynomial equations <eqn_1>, ..., <eqn_m> for the variables <x_1>, ..., <x_n>. An expression <expr> is equivalent to an equation <expr> = 0'. There may be more equations than variables or vice versa. algsys' returns a list of solutions, with each solution given as a list of equations stating values of the variables <x_1>, ..., <x_n> which satisfy the system of equations. If algsys' cannot find a solution, an empty list []' is returned. The symbols %r1', %r2', ..., are introduced as needed to represent arbitrary parameters in the solution; these variables are also appended to the list %rnum_list'. The method is as follows: 1. First the equations are factored and split into subsystems. 2. For each subsystem <S_i>, an equation <E> and a variable <x> are selected. The variable is chosen to have lowest nonzero degree. Then the resultant of <E> and <E_j> with respect to <x> is computed for each of the remaining equations <E_j> in the subsystem <S_i>. This yields a new subsystem <S_i'> in one fewer variables, as <x> has been eliminated. The process now returns to (1). 3. Eventually, a subsystem consisting of a single equation is obtained. If the equation is multivariate and no approximations in the form of floating point numbers have been introduced, then solve' is called to find an exact solution. In some cases, solve' is not be able to find a solution, or if it does the solution may be a very large expression. If the equation is univariate and is either linear, quadratic, or biquadratic, then again solve' is called if no approximations have been introduced. If approximations have been introduced or the equation is not univariate and neither linear, quadratic, or biquadratic, then if the switch realonly' is true', the function realroots' is called to find the real-valued solutions. If realonly' is false', then allroots' is called which looks for real and complex-valued solutions. If algsys' produces a solution which has fewer significant digits than required, the user can change the value of algepsilon' to a higher value. If algexact' is set to true', solve' will always be called. 4. Finally, the solutions obtained in step (3) are substituted into previous levels and the solution process returns to (1). When algsys' encounters a multivariate equation which contains floating point approximations (usually due to its failing to find exact solutions at an earlier stage), then it does not attempt to apply exact methods to such equations and instead prints the message: "algsys' cannot solve - system too complicated." Interactions with radcan' can produce large or complicated expressions. In that case, it may be possible to isolate parts of the result with pickapart' or reveal'. Occasionally, radcan' may introduce an imaginary unit %i' into a solution which is actually real-valued. Examples: (%i1) e1: 2*x*(1 - a1) - 2*(x - 1)*a2; (%o1) 2 (1 - a1) x - 2 a2 (x - 1) (%i2) e2: a2 - a1; (%o2) a2 - a1 (%i3) e3: a1*(-y - x^2 + 1); 2 (%o3) a1 (- y - x + 1) (%i4) e4: a2*(y - (x - 1)^2); 2 (%o4) a2 (y - (x - 1) ) (%i5) algsys ([e1, e2, e3, e4], [x, y, a1, a2]); (%o5) [[x = 0, y = %r1, a1 = 0, a2 = 0], [x = 1, y = 0, a1 = 1, a2 = 1]] (%i6) e1: x^2 - y^2; 2 2 (%o6) x - y (%i7) e2: -1 - y + 2*y^2 - x + x^2; 2 2 (%o7) 2 y - y + x - x - 1 (%i8) algsys ([e1, e2], [x, y]); 1 1 (%o8) [[x = - -------, y = -------], sqrt(3) sqrt(3) 1 1 1 1 [x = -------, y = - -------], [x = - -, y = - -], [x = 1, y = 1]] sqrt(3) sqrt(3) 3 3  Function: allroots   allroots (<expr>) allroots (<eqn>) Computes numerical approximations of the real and complex roots of the polynomial <expr> or polynomial equation <eqn> of one variable. The flag polyfactor' when true' causes allroots' to factor the polynomial over the real numbers if the polynomial is real, or over the complex numbers, if the polynomial is complex. allroots' may give inaccurate results in case of multiple roots. If the polynomial is real, allroots (%i*<p>)' may yield more accurate approximations than allroots (<p>)', as allroots' invokes a different algorithm in that case. allroots' rejects non-polynomials. It requires that the numerator after rat''ing should be a polynomial, and it requires that the denominator be at most a complex number. As a result of this allroots' will always return an equivalent (but factored) expression, if polyfactor' is true'. For complex polynomials an algorithm by Jenkins and Traub is used (Algorithm 419, Comm. ACM, vol. 15, (1972), p. 97). For real polynomials the algorithm used is due to Jenkins (Algorithm 493, ACM TOMS, vol. 1, (1975), p.178). Examples: (%i1) eqn: (1 + 2*x)^3 = 13.5*(1 + x^5); 3 5 (%o1) (2 x + 1) = 13.5 (x + 1) (%i2) soln: allroots (eqn); (%o2) [x = .8296749902129361, x = - 1.015755543828121, x = .9659625152196369 %i - .4069597231924075, x = - .9659625152196369 %i - .4069597231924075, x = 1.0] (%i3) for e in soln do (e2: subst (e, eqn), disp (expand (lhs(e2) - rhs(e2)))); - 3.5527136788005E-15 - 5.32907051820075E-15 4.44089209850063E-15 %i - 4.88498130835069E-15 - 4.44089209850063E-15 %i - 4.88498130835069E-15 3.5527136788005E-15 (%o3) done (%i4) polyfactor: true$
(%i5) allroots (eqn);
(%o5) - 13.5 (x - 1.0) (x - .8296749902129361)

2
(x + 1.015755543828121) (x  + .8139194463848151 x

+ 1.098699797110288)


Function: bfallroots

          bfallroots (<expr>)
bfallroots (<eqn>)
Computes numerical approximations of the real and complex roots of
the polynomial <expr> or polynomial equation <eqn> of one variable.

In all respects, bfallroots' is identical to allroots' except
that bfallroots' computes the roots using bigfloats.  See
allroots' for more information.


Option variable: backsubst

     Default value: true'

When backsubst' is false', prevents back substitution in
linsolve' after the equations have been triangularized.  This may
be helpful in very big problems where back substitution would cause
the generation of extremely large expressions.

(%i1) eq1 : x + y + z = 6$(%i2) eq2 : x - y + z = 2$
(%i3) eq3 : x + y - z = 0$(%i4) backsubst : false$
(%i5) linsolve ([eq1, eq2, eq3], [x,y,z]);
(%o5)             [x = z - y, y = 2, z = 3]
(%i6) backsubst : true$(%i7) linsolve ([eq1, eq2, eq3], [x,y,z]); (%o7) [x = 1, y = 2, z = 3]  Option variable: breakup   Default value: true' When breakup' is true', solve' expresses solutions of cubic and quartic equations in terms of common subexpressions, which are assigned to intermediate expression labels (%t1', %t2', etc.). Otherwise, common subexpressions are not identified. breakup: true' has an effect only when programmode' is false'. Examples: (%i1) programmode: false$
(%i2) breakup: true$(%i3) solve (x^3 + x^2 - 1); sqrt(23) 25 1/3 (%t3) (--------- + --) 6 sqrt(3) 54 Solution: sqrt(3) %i 1 ---------- - - sqrt(3) %i 1 2 2 1 (%t4) x = (- ---------- - -) %t3 + -------------- - - 2 2 9 %t3 3 sqrt(3) %i 1 - ---------- - - sqrt(3) %i 1 2 2 1 (%t5) x = (---------- - -) %t3 + ---------------- - - 2 2 9 %t3 3 1 1 (%t6) x = %t3 + ----- - - 9 %t3 3 (%o6) [%t4, %t5, %t6] (%i6) breakup: false$
(%i7) solve (x^3 + x^2 - 1);
Solution:

sqrt(3) %i   1
---------- - -
2        2        sqrt(23)    25 1/3
(%t7) x = --------------------- + (--------- + --)
sqrt(23)    25 1/3    6 sqrt(3)   54
9 (--------- + --)
6 sqrt(3)   54

sqrt(3) %i   1    1
(- ---------- - -) - -
2        2    3
sqrt(23)    25 1/3  sqrt(3) %i   1
(%t8) x = (--------- + --)    (---------- - -)
6 sqrt(3)   54          2        2

sqrt(3) %i   1
- ---------- - -
2        2      1
+ --------------------- - -
sqrt(23)    25 1/3   3
9 (--------- + --)
6 sqrt(3)   54
sqrt(23)    25 1/3             1             1
(%t9)  x = (--------- + --)    + --------------------- - -
6 sqrt(3)   54          sqrt(23)    25 1/3   3
9 (--------- + --)
6 sqrt(3)   54
(%o9)                    [%t7, %t8, %t9]


Function: dimension

          dimension (<eqn>)
dimension (<eqn_1>, ..., <eqn_n>)
dimen' is a package for dimensional analysis.  load ("dimen")'
loads this package.  demo ("dimen")' displays a short
demonstration.


Option variable: dispflag

     Default value: true'

If set to false' within a block' will inhibit the display of
output generated by the solve functions called from within the
block'.  Termination of the block' with a dollar sign, $, sets dispflag' to false'.  Function: funcsolve (<eqn>, <g>(<t>))   Returns [<g>(<t>) = ...]' or []', depending on whether or not there exists a rational function <g>(<t>)' satisfying <eqn>, which must be a first order, linear polynomial in (for this case) <g>(<t>)' and <g>(<t>+1)' (%i1) eqn: (n + 1)*f(n) - (n + 3)*f(n + 1)/(n + 1) = (n - 1)/(n + 2); (n + 3) f(n + 1) n - 1 (%o1) (n + 1) f(n) - ---------------- = ----- n + 1 n + 2 (%i2) funcsolve (eqn, f(n)); Dependent equations eliminated: (4 3) n (%o2) f(n) = --------------- (n + 1) (n + 2) Warning: this is a very rudimentary implementation - many safety checks and obvious generalizations are missing.  Option variable: globalsolve   Default value: false' When globalsolve' is true', solved-for variables are assigned the solution values found by linsolve', and by solve' when solving two or more linear equations. When globalsolve' is false', solutions found by linsolve' and by solve' when solving two or more linear equations are expressed as equations, and the solved-for variables are not assigned. When solving anything other than two or more linear equations, solve' ignores globalsolve'. Other functions which solve equations (e.g., algsys') always ignore globalsolve'. Examples: (%i1) globalsolve: true$
(%i2) solve ([x + 3*y = 2, 2*x - y = 5], [x, y]);
Solution

17
(%t2)                        x : --
7

1
(%t3)                        y : - -
7
(%o3)                     [[%t2, %t3]]
(%i3) x;
17
(%o3)                          --
7
(%i4) y;
1
(%o4)                          - -
7
(%i5) globalsolve: false$(%i6) kill (x, y)$
(%i7) solve ([x + 3*y = 2, 2*x - y = 5], [x, y]);
Solution

17
(%t7)                        x = --
7

1
(%t8)                        y = - -
7
(%o8)                     [[%t7, %t8]]
(%i8) x;
(%o8)                           x
(%i9) y;
(%o9)                           y


Function: ieqn (<ie>, <unk>, <tech>, <n>, <guess>)

     inteqn' is a package for solving integral equations.  load

<ie> is the integral equation; <unk> is the unknown function;
<tech> is the technique to be tried from those given above (<tech>
= first' means: try the first technique which finds a solution;
<tech> = all' means: try all applicable techniques); <n> is the
maximum number of terms to take for taylor', neumann',
firstkindseries', or fredseries' (it is also the maximum depth
of recursion for the differentiation method); <guess> is the
initial guess for neumann' or firstkindseries'.

Default values for the 2nd thru 5th parameters are:

<unk>: <p>(<x>)', where <p> is the first function encountered in
an integrand which is unknown to Maxima and <x> is the variable
which occurs as an argument to the first occurrence of <p> found
outside of an integral in the case of secondkind' equations, or
is the only other variable besides the variable of integration in
firstkind' equations.  If the attempt to search for <x> fails,
the user will be asked to supply the independent variable.

tech: first'

n: 1

guess: none' which will cause neumann' and firstkindseries' to
use <f>(<x>)' as an initial guess.


Option variable: ieqnprint

     Default value: true'

ieqnprint' governs the behavior of the result returned by the
ieqn' command.  When ieqnprint' is false', the lists returned
by the ieqn' function are of the form

[<solution>, <technique used>, <nterms>, <flag>]

where <flag> is absent if the solution is exact.

Otherwise, it is the word approximate' or incomplete'
corresponding to an inexact or non-closed form solution,
respectively.  If a series method was used, <nterms> gives the
number of terms taken (which could be less than the n given to
ieqn' if an error prevented generation of further terms).


Function: lhs (<expr>)

     Returns the left-hand side (that is, the first argument) of the
expression <expr>, when the operator of <expr> is one of the
relational operators < <= = # equal notequal >= >', one of the
assignment operators := ::= : ::', or a user-defined binary infix
operator, as declared by infix'.

When <expr> is an atom or its operator is something other than the
ones listed above, lhs' returns <expr>.

Examples:

(%i1) e: aa + bb = cc;
(%o1)                     bb + aa = cc
(%i2) lhs (e);
(%o2)                        bb + aa
(%i3) rhs (e);
(%o3)                          cc
(%i4) [lhs (aa < bb), lhs (aa <= bb), lhs (aa >= bb),
lhs (aa > bb)];
(%o4)                   [aa, aa, aa, aa]
(%i5) [lhs (aa = bb), lhs (aa # bb), lhs (equal (aa, bb)),
lhs (notequal (aa, bb))];
(%o5)                   [aa, aa, aa, aa]
(%i6) e1: '(foo(x) := 2*x);
(%o6)                     foo(x) := 2 x
(%i7) e2: '(bar(y) ::= 3*y);
(%o7)                    bar(y) ::= 3 y
(%i8) e3: '(x : y);
(%o8)                         x : y
(%i9) e4: '(x :: y);
(%o9)                        x :: y
(%i10) [lhs (e1), lhs (e2), lhs (e3), lhs (e4)];
(%o10)               [foo(x), bar(y), x, x]
(%i11) infix ("][");
(%o11)                         ][
(%i12) lhs (aa ][ bb);
(%o12)                         aa


Function: linsolve ([<expr_1>, ..., <expr_m>], [<x_1>, ..., <x_n>])

     Solves the list of simultaneous linear equations for the list of
variables.  The expressions must each be polynomials in the
variables and may be equations.

When globalsolve' is true', each solved-for variable is bound to
its value in the solution of the equations.

When backsubst' is false', linsolve' does not carry out back
substitution after the equations have been triangularized.  This
may be necessary in very big problems where back substitution
would cause the generation of extremely large expressions.

When linsolve_params' is true', linsolve' also generates the
%r' symbols used to represent arbitrary parameters described in
the manual under algsys'.  Otherwise, linsolve' solves an
under-determined system of equations with some variables expressed
in terms of others.

When programmode' is false', linsolve' displays the solution
with intermediate expression (%t') labels, and returns the list
of labels.

(%i1) e1: x + z = y;
(%o1)                       z + x = y
(%i2) e2: 2*a*x - y = 2*a^2;
2
(%o2)                   2 a x - y = 2 a
(%i3) e3: y - 2*z = 2;
(%o3)                      y - 2 z = 2
(%i4) [globalsolve: false, programmode: true];
(%o4)                     [false, true]
(%i5) linsolve ([e1, e2, e3], [x, y, z]);
(%o5)            [x = a + 1, y = 2 a, z = a - 1]
(%i6) [globalsolve: false, programmode: false];
(%o6)                    [false, false]
(%i7) linsolve ([e1, e2, e3], [x, y, z]);
Solution

(%t7)                       z = a - 1

(%t8)                        y = 2 a

(%t9)                       x = a + 1
(%o9)                    [%t7, %t8, %t9]
(%i9) ''%;
(%o9)            [z = a - 1, y = 2 a, x = a + 1]
(%i10) [globalsolve: true, programmode: false];
(%o10)                    [true, false]
(%i11) linsolve ([e1, e2, e3], [x, y, z]);
Solution

(%t11)                      z : a - 1

(%t12)                       y : 2 a

(%t13)                      x : a + 1
(%o13)                 [%t11, %t12, %t13]
(%i13) ''%;
(%o13)           [z : a - 1, y : 2 a, x : a + 1]
(%i14) [x, y, z];
(%o14)                 [a + 1, 2 a, a - 1]
(%i15) [globalsolve: true, programmode: true];
(%o15)                    [true, true]
(%i16) linsolve ([e1, e2, e3], '[x, y, z]);
(%o16)           [x : a + 1, y : 2 a, z : a - 1]
(%i17) [x, y, z];
(%o17)                 [a + 1, 2 a, a - 1]


Option variable: linsolvewarn

     Default value: true'

When linsolvewarn' is true', linsolve' prints a message
"Dependent equations eliminated".


Option variable: linsolve_params

     Default value: true'

When linsolve_params' is true', linsolve' also generates the
%r' symbols used to represent arbitrary parameters described in
the manual under algsys'.  Otherwise, linsolve' solves an
under-determined system of equations with some variables expressed
in terms of others.


System variable: multiplicities

     Default value: not_set_yet'

multiplicities' is set to a list of the multiplicities of the
individual solutions returned by solve' or realroots'.


Function: nroots (<p>, <low>, <high>)

     Returns the number of real roots of the real univariate polynomial
<p> in the half-open interval (<low>, <high>]'.  The endpoints of
the interval may be minf' or inf'.

nroots' uses the method of Sturm sequences.

(%i1) p: x^10 - 2*x^4 + 1/2$(%i2) nroots (p, -6, 9.1); (%o2) 4  Function: nthroot (<p>, <n>)   where <p> is a polynomial with integer coefficients and <n> is a positive integer returns q', a polynomial over the integers, such that q^n = p' or prints an error message indicating that <p> is not a perfect nth power. This routine is much faster than factor' or even sqfr'.  Option variable: polyfactor   Default value: false' The option variable polyfactor' when true' causes allroots' and bfallroots' to factor the polynomial over the real numbers if the polynomial is real, or over the complex numbers, if the polynomial is complex. See allroots' for an example.  Option variable: programmode   Default value: true' When programmode' is true', solve', realroots', allroots', and linsolve' return solutions as elements in a list. (Except when backsubst' is set to false', in which case programmode: false' is assumed.) When programmode' is false', solve', etc. create intermediate expression labels %t1', t2', etc., and assign the solutions to them.  Option variable: realonly   Default value: false' When realonly' is true', algsys' returns only those solutions which are free of %i'.  Function: realroots   realroots (<expr>, <bound>) realroots (<eqn>, <bound>) realroots (<expr>) realroots (<eqn>) Computes rational approximations of the real roots of the polynomial <expr> or polynomial equation <eqn> of one variable, to within a tolerance of <bound>. Coefficients of <expr> or <eqn> must be literal numbers; symbol constants such as %pi' are rejected. realroots' assigns the multiplicities of the roots it finds to the global variable multiplicities'. realroots' constructs a Sturm sequence to bracket each root, and then applies bisection to refine the approximations. All coefficients are converted to rational equivalents before searching for roots, and computations are carried out by exact rational arithmetic. Even if some coefficients are floating-point numbers, the results are rational (unless coerced to floats by the float' or numer' flags). When <bound> is less than 1, all integer roots are found exactly. When <bound> is unspecified, it is assumed equal to the global variable rootsepsilon'. When the global variable programmode' is true', realroots' returns a list of the form [x = <x_1>, x = <x_2>, ...]'. When programmode' is false', realroots' creates intermediate expression labels %t1', %t2', ..., assigns the results to them, and returns the list of labels. Examples: (%i1) realroots (-1 - x + x^5, 5e-6); 612003 (%o1) [x = ------] 524288 (%i2) ev (%, float); (%o2) x = 1.167303085327148 (%i3) ev (-1 - x + x^5, %); (%o3) - 7.396496210176905E-6 (%i1) realroots (expand ((1 - x)^5 * (2 - x)^3 * (3 - x)), 1e-20); (%o1) [x = 1, x = 2, x = 3] (%i2) multiplicities; (%o2) [5, 3, 1]  Function: rhs (<expr>)   Returns the right-hand side (that is, the second argument) of the expression <expr>, when the operator of <expr> is one of the relational operators < <= = # equal notequal >= >', one of the assignment operators := ::= : ::', or a user-defined binary infix operator, as declared by infix'. When <expr> is an atom or its operator is something other than the ones listed above, rhs' returns 0. See also lhs'. Examples: (%i1) e: aa + bb = cc; (%o1) bb + aa = cc (%i2) lhs (e); (%o2) bb + aa (%i3) rhs (e); (%o3) cc (%i4) [rhs (aa < bb), rhs (aa <= bb), rhs (aa >= bb), rhs (aa > bb)]; (%o4) [bb, bb, bb, bb] (%i5) [rhs (aa = bb), rhs (aa # bb), rhs (equal (aa, bb)), rhs (notequal (aa, bb))]; (%o5) [bb, bb, bb, bb] (%i6) e1: '(foo(x) := 2*x); (%o6) foo(x) := 2 x (%i7) e2: '(bar(y) ::= 3*y); (%o7) bar(y) ::= 3 y (%i8) e3: '(x : y); (%o8) x : y (%i9) e4: '(x :: y); (%o9) x :: y (%i10) [rhs (e1), rhs (e2), rhs (e3), rhs (e4)]; (%o10) [2 x, 3 y, y, y] (%i11) infix ("]["); (%o11) ][ (%i12) rhs (aa ][ bb); (%o12) bb  Option variable: rootsconmode   Default value: true' rootsconmode' governs the behavior of the rootscontract' command. See rootscontract' for details.  Function: rootscontract (<expr>)   Converts products of roots into roots of products. For example, rootscontract (sqrt(x)*y^(3/2))' yields sqrt(x*y^3)'. When radexpand' is true' and domain' is real', rootscontract' converts abs' into sqrt', e.g., rootscontract (abs(x)*sqrt(y))' yields sqrt(x^2*y)'. There is an option rootsconmode' affecting rootscontract' as follows: Problem Value of Result of applying rootsconmode rootscontract x^(1/2)*y^(3/2) false (x*y^3)^(1/2) x^(1/2)*y^(1/4) false x^(1/2)*y^(1/4) x^(1/2)*y^(1/4) true (x*y^(1/2))^(1/2) x^(1/2)*y^(1/3) true x^(1/2)*y^(1/3) x^(1/2)*y^(1/4) all (x^2*y)^(1/4) x^(1/2)*y^(1/3) all (x^3*y^2)^(1/6) When rootsconmode' is false', rootscontract' contracts only with respect to rational number exponents whose denominators are the same. The key to the rootsconmode: true' examples is simply that 2 divides into 4 but not into 3. rootsconmode: all' involves taking the least common multiple of the denominators of the exponents. rootscontract' uses ratsimp' in a manner similar to logcontract'. Examples: (%i1) rootsconmode: false$
(%i2) rootscontract (x^(1/2)*y^(3/2));
3
(%o2)                      sqrt(x y )
(%i3) rootscontract (x^(1/2)*y^(1/4));
1/4
(%o3)                     sqrt(x) y
(%i4) rootsconmode: true$(%i5) rootscontract (x^(1/2)*y^(1/4)); (%o5) sqrt(x sqrt(y)) (%i6) rootscontract (x^(1/2)*y^(1/3)); 1/3 (%o6) sqrt(x) y (%i7) rootsconmode: all$
(%i8) rootscontract (x^(1/2)*y^(1/4));
2   1/4
(%o8)                       (x  y)
(%i9) rootscontract (x^(1/2)*y^(1/3));
3  2 1/6
(%o9)                      (x  y )
(%i10) rootsconmode: false$(%i11) rootscontract (sqrt(sqrt(x) + sqrt(1 + x)) *sqrt(sqrt(1 + x) - sqrt(x))); (%o11) 1 (%i12) rootsconmode: true$
(%i13) rootscontract (sqrt(5+sqrt(5)) - 5^(1/4)*sqrt(1+sqrt(5)));
(%o13)                          0


Option variable: rootsepsilon

     Default value: 1.0e-7

rootsepsilon' is the tolerance which establishes the confidence
interval for the roots found by the realroots' function.


Function: solve

          solve (<expr>, <x>)
solve (<expr>)
solve ([<eqn_1>, ..., <eqn_n>], [<x_1>, ..., <x_n>])
Solves the algebraic equation <expr> for the variable <x> and
returns a list of solution equations in <x>.  If <expr> is not an
equation, the equation <expr> = 0' is assumed in its place.  <x>
may be a function (e.g. f(x)'), or other non-atomic expression
except a sum or product.  <x> may be omitted if <expr> contains
only one variable.  <expr> may be a rational expression, and may
contain trigonometric functions, exponentials, etc.

The following method is used:

Let <E> be the expression and <X> be the variable.  If <E> is
linear in <X> then it is trivially solved for <X>.  Otherwise if
<E> is of the form A*X^N + B' then the result is (-B/A)^1/N)'
times the N''th roots of unity.

If <E> is not linear in <X> then the gcd of the exponents of <X> in
<E> (say <N>) is divided into the exponents and the multiplicity
of the roots is multiplied by <N>.  Then solve' is called again
on the result.  If <E> factors then solve' is called on each of
the factors.  Finally solve' will use the quadratic, cubic, or
quartic formulas where necessary.

In the case where <E> is a polynomial in some function of the
variable to be solved for, say F(X)', then it is first solved for
F(X)' (call the result <C>), then the equation F(X)=C' can be
solved for <X> provided the inverse of the function <F> is known.

breakup' if false' will cause solve' to express the solutions
of cubic or quartic equations as single expressions rather than as
made up of several common subexpressions which is the default.

multiplicities' - will be set to a list of the multiplicities of
the individual solutions returned by solve', realroots', or
allroots'.  Try apropos (solve)' for the switches which affect
solve'.  describe' may then by used on the individual switch
names if their purpose is not clear.

solve ([<eqn_1>, ..., <eqn_n>], [<x_1>, ..., <x_n>])' solves a
system of simultaneous (linear or non-linear) polynomial equations
by calling linsolve' or algsys' and returns a list of the
solution lists in the variables.  In the case of linsolve' this
list would contain a single list of solutions.  It takes two lists
as arguments.  The first list represents the equations to be
solved; the second list is a list of the unknowns to be
determined.  If the total number of variables in the equations is
equal to the number of equations, the second argument-list may be
omitted.

When programmode' is false', solve' displays solutions with
intermediate expression (%t') labels, and returns the list of
labels.

When globalsolve' is true' and the problem is to solve two or
more linear equations, each solved-for variable is bound to its
value in the solution of the equations.

Examples:

(%i1) solve (asin (cos (3*x))*(f(x) - 1), x);

solve: using arc-trig functions to get a solution.
Some solutions will be lost.
%pi
(%o1)                  [x = ---, f(x) = 1]
6
(%i2) ev (solve (5^f(x) = 125, f(x)), solveradcan);
log(125)
(%o2)                   [f(x) = --------]
log(5)
(%i3) [4*x^2 - y^2 = 12, x*y - x = 2];
2    2
(%o3)             [4 x  - y  = 12, x y - x = 2]

(%i4) solve (%, [x, y]);
(%o4) [[x = 2, y = 2], [x = .5202594388652008 %i
- .1331240357358706, y = .07678378523787788
- 3.608003221870287 %i], [x = - .5202594388652008 %i
- .1331240357358706, y = 3.608003221870287 %i
+ .07678378523787788], [x = - 1.733751846381093,
y = - .1535675710019696]]

(%i5) solve (1 + a*x + x^3, x);

3
sqrt(3) %i   1   sqrt(4 a  + 27)   1 1/3
(%o5) [x = (- ---------- - -) (--------------- - -)
2        2      6 sqrt(3)      2

sqrt(3) %i   1
(---------- - -) a
2        2
- --------------------------, x =
3
sqrt(4 a  + 27)   1 1/3
3 (--------------- - -)
6 sqrt(3)      2

3
sqrt(3) %i   1   sqrt(4 a  + 27)   1 1/3
(---------- - -) (--------------- - -)
2        2      6 sqrt(3)      2

sqrt(3) %i   1
(- ---------- - -) a
2        2
- --------------------------, x =
3
sqrt(4 a  + 27)   1 1/3
3 (--------------- - -)
6 sqrt(3)      2

3
sqrt(4 a  + 27)   1 1/3               a
(--------------- - -)    - --------------------------]
6 sqrt(3)      2                  3
sqrt(4 a  + 27)   1 1/3
3 (--------------- - -)
6 sqrt(3)      2
(%i6) solve (x^3 - 1);
sqrt(3) %i - 1        sqrt(3) %i + 1
(%o6)   [x = --------------, x = - --------------, x = 1]
2                     2
(%i7) solve (x^6 - 1);
sqrt(3) %i + 1      sqrt(3) %i - 1
(%o7) [x = --------------, x = --------------, x = - 1,
2                   2

sqrt(3) %i + 1        sqrt(3) %i - 1
x = - --------------, x = - --------------, x = 1]
2                     2
(%i8) ev (x^6 - 1, %);
6
(sqrt(3) %i + 1)
(%o8)                 ----------------- - 1
64
(%i9) expand (%);
(%o9)                           0
(%i10) x^2 - 1;
2
(%o10)                       x  - 1
(%i11) solve (%, x);
(%o11)                  [x = - 1, x = 1]
(%i12) ev (%th(2), %);
(%o12)                          0

The symbols %r' are used to denote arbitrary constants in a
solution.

(%i1) solve([x+y=1,2*x+2*y=2],[x,y]);

solve: dependent equations eliminated: (2)
(%o1)                      [[x = 1 - %r1, y = %r1]]

See algsys' and %rnum_list' for more information.


Option variable: solvedecomposes

     Default value: true'

When solvedecomposes' is true', solve' calls polydecomp' if


Option variable: solveexplicit

     Default value: false'

When solveexplicit' is true', inhibits solve' from returning
implicit solutions, that is, solutions of the form F(x) = 0' where
F' is some function.


Option variable: solvefactors

     Default value: true'

When solvefactors' is false', solve' does not try to factor the
expression.  The false' setting may be desired in some cases where
factoring is not necessary.


Option variable: solvenullwarn

     Default value: true'

When solvenullwarn' is true', solve' prints a warning message
if called with either a null equation list or a null variable
list.  For example, solve ([], [])' would print two warning
messages and return []'.


Option variable: solveradcan

     Default value: false'

When solveradcan' is true', solve' calls radcan' which makes
solve' slower but will allow certain problems containing
exponentials and logarithms to be solved.


Option variable: solvetrigwarn

     Default value: true'

When solvetrigwarn' is true', solve' may print a message saying
that it is using inverse trigonometric functions to solve the
equation, and thereby losing solutions.



## 21 Differential Equations


Introduction to Differential Equations
Functions and Variables for Differential Equations


## 21.1 Introduction to Differential Equations

This section describes the functions available in Maxima to obtain
analytic solutions for some specific types of first and second-order
equations. To obtain a numerical solution for a system of differential
equations, see the additional package dynamics'. For graphical
representations in phase space, see the additional package plotdf'.


## 21.2 Functions and Variables for Differential Equations

Function: bc2 (<solution>, <xval1>, <yval1>, <xval2>, <yval2>)

     Solves a boundary value problem for a second order differential
equation.  Here: <solution> is a general solution to the equation,
as found by ode2'; <xval1> specifies the value of the independent
variable in a first point, in the form <x> = <x1>', and <yval1>
gives the value of the dependent variable in that point, in the
form <y> = <y1>'. The expressions <xval2> and <yval2> give the
values for these variables at a second point, using the same form.

See ode2' for an example of its usage.


Function: desolve

          desolve (<eqn>, <x>)
desolve ([<eqn_1>, ..., <eqn_n>], [<x_1>, ..., <x_n>])
The function desolve' solves systems of linear ordinary
differential equations using Laplace transform.  Here the <eqn>'s
are differential equations in the dependent variables <x_1>, ...,
<x_n>.  The functional dependence of <x_1>, ..., <x_n> on an
independent variable, for instance <x>, must be explicitly
indicated in the variables and its derivatives. For example, this
would not be the correct way to define two equations:

eqn_1: 'diff(f,x,2) = sin(x) + 'diff(g,x);
eqn_2: 'diff(f,x) + x^2 - f = 2*'diff(g,x,2);

The correct way would be:

eqn_1: 'diff(f(x),x,2) = sin(x) + 'diff(g(x),x);
eqn_2: 'diff(f(x),x) + x^2 - f(x) = 2*'diff(g(x),x,2);

The call to the function desolve' would then be
desolve([eqn_1, eqn_2], [f(x),g(x)]);

If initial conditions at x=0' are known, they can be supplied
before calling desolve' by using atvalue'.

(%i1) 'diff(f(x),x)='diff(g(x),x)+sin(x);
d           d
(%o1)            -- (f(x)) = -- (g(x)) + sin(x)
dx          dx
(%i2) 'diff(g(x),x,2)='diff(f(x),x)-cos(x);
2
d            d
(%o2)            --- (g(x)) = -- (f(x)) - cos(x)
2          dx
dx
(%i3) atvalue('diff(g(x),x),x=0,a);
(%o3)                           a
(%i4) atvalue(f(x),x=0,1);
(%o4)                           1
(%i5) desolve([%o1,%o2],[f(x),g(x)]);
x
(%o5) [f(x) = a %e  - a + 1, g(x) =

x
cos(x) + a %e  - a + g(0) - 1]
(%i6) [%o1,%o2],%o5,diff;
x       x      x                x
(%o6)   [a %e  = a %e , a %e  - cos(x) = a %e  - cos(x)]

If desolve' cannot obtain a solution, it returns false'.


Function: ic1 (<solution>, <xval>, <yval>)

     Solves initial value problems for first order differential
equations.  Here <solution> is a general solution to the equation,
as found by ode2', <xval> gives an initial value for the
independent variable in the form <x> = <x0>', and <yval> gives the
initial value for the dependent variable in the form <y> = <y0>'.

See ode2' for an example of its usage.


Function: ic2 (<solution>, <xval>, <yval>, <dval>)

     Solves initial value problems for second-order differential
equations.  Here <solution> is a general solution to the equation,
as found by ode2', <xval> gives the initial value for the
independent variable in the form <x> = <x0>', <yval> gives the
initial value of the dependent variable in the form <y> = <y0>',
and <dval> gives the initial value for the first derivative of the
dependent variable with respect to independent variable, in the
form diff(<y>,<x>) = <dy0>' (diff' does not have to be quoted).

See ode2' for an example of its usage.


Function: ode2 (<eqn>, <dvar>, <ivar>)

     The function ode2' solves an ordinary differential equation (ODE)
of first or second order. It takes three arguments: an ODE given by
<eqn>, the dependent variable <dvar>, and the independent variable
<ivar>. When successful, it returns either an explicit or implicit
solution for the dependent variable. %c' is used to represent the
integration constant in the case of first-order equations, and
%k1' and %k2' the constants for second-order equations. The
dependence of the dependent variable on the independent variable
does not have to be written explicitly, as in the case of
desolve', but the independent variable must always be given as the
third argument.

If ode2' cannot obtain a solution for whatever reason, it returns
false', after perhaps printing out an error message. The methods
implemented for first order equations in the order in which they
are tested are: linear, separable, exact - perhaps requiring an
integrating factor, homogeneous, Bernoulli's equation, and a
generalized homogeneous method. The types of second-order
equations which can be solved are: constant coefficients, exact,
linear homogeneous with non-constant coefficients which can be
transformed to constant coefficients, the Euler or
equi-dimensional equation, equations solvable by the method of
variation of parameters, and equations which are free of either the
independent or of the dependent variable so that they can be
reduced to two first order linear equations to be solved
sequentially.

In the course of solving ODE's, several variables are set purely
for informational purposes: method' denotes the method of solution
used (e.g., linear'), intfactor' denotes any integrating factor
used, odeindex' denotes the index for Bernoulli's method or for
the generalized homogeneous method, and yp' denotes the
particular solution for the variation of parameters technique.

In order to solve initial value problems (IVP) functions ic1' and
ic2' are available for first and second order equations, and to
solve second-order boundary value problems (BVP) the function bc2'
can be used.

Example:

(%i1) x^2*'diff(y,x) + 3*y*x = sin(x)/x;
2 dy           sin(x)
(%o1)                x  -- + 3 x y = ------
dx             x
(%i2) ode2(%,y,x);
%c - cos(x)
(%o2)                    y = -----------
3
x
(%i3) ic1(%o2,x=%pi,y=0);
cos(x) + 1
(%o3)                   y = - ----------
3
x
(%i4) 'diff(y,x,2) + y*'diff(y,x)^3 = 0;
2
d y      dy 3
(%o4)                   --- + y (--)  = 0
2      dx
dx
(%i5) ode2(%,y,x);
3
y  + 6 %k1 y
(%o5)                ------------ = x + %k2
6
(%i6) ratsimp(ic2(%o5,x=0,y=0,'diff(y,x)=2));
3
2 y  - 3 y
(%o6)                   - ---------- = x
6
(%i7) bc2(%o5,x=0,y=1,x=1,y=3);
3
y  - 10 y       3
(%o7)                   --------- = x - -
6           2



## 22 Numerical


Introduction to fast Fourier transform
Functions and Variables for fast Fourier transform
Functions for numerical solution of equations
Introduction to numerical solution of differential equations
Functions for numerical solution of differential equations


## 22.1 Introduction to fast Fourier transform

The fft' package comprises functions for the numerical (not symbolic)
computation of the fast Fourier transform.


## 22.2 Functions and Variables for fast Fourier transform

Function: polartorect (<r>, <t>)

     Translates complex values of the form r %e^(%i t)' to the form a
+ b %i', where <r> is the magnitude and <t> is the phase.  <r> and
<t> are 1-dimensional arrays of the same size.  The array size
need not be a power of 2.

The original values of the input arrays are replaced by the real
and imaginary parts, a' and b', on return.  The outputs are
calculated as

a = r cos(t)
b = r sin(t)

polartorect' is the inverse function of recttopolar'.

load(fft)' loads this function.  See also fft'.


Function: recttopolar (<a>, <b>)

     Translates complex values of the form a + b %i' to the form r
%e^(%i t)', where <a> is the real part and <b> is the imaginary
part.  <a> and <b> are 1-dimensional arrays of the same size.  The
array size need not be a power of 2.

The original values of the input arrays are replaced by the
magnitude and angle, r' and t', on return.  The outputs are
calculated as

r = sqrt(a^2 + b^2)
t = atan2(b, a)

The computed angle is in the range -%pi' to %pi'.

recttopolar' is the inverse function of polartorect'.

load(fft)' loads this function.  See also fft'.


Function: inverse_fft (<y>)

     Computes the inverse complex fast Fourier transform.  <y> is a
list or array (named or unnamed) which contains the data to
transform.  The number of elements must be a power of 2.  The
elements must be literal numbers (integers, rationals, floats, or
bigfloats) or symbolic constants, or expressions a + b*%i' where
a' and b' are literal numbers or symbolic constants.

inverse_fft' returns a new object of the same type as <y>, which
is not modified.  Results are always computed as floats or
expressions a + b*%i' where a' and b' are floats.

The inverse discrete Fourier transform is defined as follows.  Let
x' be the output of the inverse transform.  Then for j' from 0
through n - 1',

x[j] = sum(y[k] exp(-2 %i %pi j k / n), k, 0, n - 1)

As there are various sign and normalization conventions possible,
this definition of the transform may differ from that used by
other mathematical software.

See also fft' (forward transform), recttopolar', and
polartorect'.

Examples:

Real data.

(%i1) load (fft) $(%i2) fpprintprec : 4$
(%i3) L : [1, 2, 3, 4, -1, -2, -3, -4] $(%i4) L1 : inverse_fft (L); (%o4) [0.0, 14.49 %i - .8284, 0.0, 2.485 %i + 4.828, 0.0, 4.828 - 2.485 %i, 0.0, - 14.49 %i - .8284] (%i5) L2 : fft (L1); (%o5) [1.0, 2.0 - 2.168L-19 %i, 3.0 - 7.525L-20 %i, 4.0 - 4.256L-19 %i, - 1.0, 2.168L-19 %i - 2.0, 7.525L-20 %i - 3.0, 4.256L-19 %i - 4.0] (%i6) lmax (abs (L2 - L)); (%o6) 3.545L-16 Complex data. (%i1) load (fft)$
(%i2) fpprintprec : 4 $(%i3) L : [1, 1 + %i, 1 - %i, -1, -1, 1 - %i, 1 + %i, 1]$
(%i4) L1 : inverse_fft (L);
(%o4) [4.0, 2.711L-19 %i + 4.0, 2.0 %i - 2.0,
- 2.828 %i - 2.828, 0.0, 5.421L-20 %i + 4.0, - 2.0 %i - 2.0,
2.828 %i + 2.828]
(%i5) L2 : fft (L1);
(%o5) [4.066E-20 %i + 1.0, 1.0 %i + 1.0, 1.0 - 1.0 %i,
1.55L-19 %i - 1.0, - 4.066E-20 %i - 1.0, 1.0 - 1.0 %i,
1.0 %i + 1.0, 1.0 - 7.368L-20 %i]
(%i6) lmax (abs (L2 - L));
(%o6)                       6.841L-17


Function: fft (<x>)

     Computes the complex fast Fourier transform.  <x> is a list or
array (named or unnamed) which contains the data to transform.
The number of elements must be a power of 2.  The elements must be
literal numbers (integers, rationals, floats, or bigfloats) or
symbolic constants, or expressions a + b*%i' where a' and b'
are literal numbers or symbolic constants.

fft' returns a new object of the same type as <x>, which is not
modified.  Results are always computed as floats or expressions a
+ b*%i' where a' and b' are floats.

The discrete Fourier transform is defined as follows.  Let y' be
the output of the transform.  Then for k' from 0 through n - 1',

y[k] = (1/n) sum(x[j] exp(+2 %i %pi j k / n), j, 0, n - 1)

As there are various sign and normalization conventions possible,
this definition of the transform may differ from that used by
other mathematical software.

When the data <x> are real, real coefficients a' and b' can be
computed such that

x[j] = sum(a[k]*cos(2*%pi*j*k/n)+b[k]*sin(2*%pi*j*k/n), k, 0, n/2)

with

a = realpart (y)
b = 0

and, for k from 1 through n/2 - 1,

a[k] = realpart (y[k] + y[n - k])
b[k] = imagpart (y[n - k] - y[k])

and

a[n/2] = realpart (y[n/2])
b[n/2] = 0

See also inverse_fft' (inverse transform), recttopolar', and
polartorect'.

Examples:

Real data.

(%i1) load (fft) $(%i2) fpprintprec : 4$
(%i3) L : [1, 2, 3, 4, -1, -2, -3, -4] $(%i4) L1 : fft (L); (%o4) [0.0, - 1.811 %i - .1036, 0.0, .6036 - .3107 %i, 0.0, .3107 %i + .6036, 0.0, 1.811 %i - .1036] (%i5) L2 : inverse_fft (L1); (%o5) [1.0, 2.168L-19 %i + 2.0, 7.525L-20 %i + 3.0, 4.256L-19 %i + 4.0, - 1.0, - 2.168L-19 %i - 2.0, - 7.525L-20 %i - 3.0, - 4.256L-19 %i - 4.0] (%i6) lmax (abs (L2 - L)); (%o6) 3.545L-16 Complex data. (%i1) load (fft)$
(%i2) fpprintprec : 4 $(%i3) L : [1, 1 + %i, 1 - %i, -1, -1, 1 - %i, 1 + %i, 1]$
(%i4) L1 : fft (L);
(%o4) [0.5, .3536 %i + .3536, - 0.25 %i - 0.25,
0.5 - 6.776L-21 %i, 0.0, - .3536 %i - .3536, 0.25 %i - 0.25,
0.5 - 3.388L-20 %i]
(%i5) L2 : inverse_fft (L1);
(%o5) [1.0 - 4.066E-20 %i, 1.0 %i + 1.0, 1.0 - 1.0 %i,
- 1.008L-19 %i - 1.0, 4.066E-20 %i - 1.0, 1.0 - 1.0 %i,
1.0 %i + 1.0, 1.947L-20 %i + 1.0]
(%i6) lmax (abs (L2 - L));
(%o6)                       6.83L-17

Computation of sine and cosine coefficients.

(%i1) load (fft) $(%i2) fpprintprec : 4$
(%i3) L : [1, 2, 3, 4, 5, 6, 7, 8] $(%i4) n : length (L)$
(%i5) x : make_array (any, n) $(%i6) fillarray (x, L)$
(%i7) y : fft (x) $(%i8) a : make_array (any, n/2 + 1)$
(%i9) b : make_array (any, n/2 + 1) $(%i10) a : realpart (y)$
(%i11) b : 0 $(%i12) for k : 1 thru n/2 - 1 do (a[k] : realpart (y[k] + y[n - k]), b[k] : imagpart (y[n - k] - y[k])); (%o12) done (%i13) a[n/2] : y[n/2]$
(%i14) b[n/2] : 0 $(%i15) listarray (a); (%o15) [4.5, - 1.0, - 1.0, - 1.0, - 0.5] (%i16) listarray (b); (%o16) [0, - 2.414, - 1.0, - .4142, 0] (%i17) f(j) := sum (a[k]*cos(2*%pi*j*k/n) + b[k]*sin(2*%pi*j*k/n), k, 0, n/2)$
(%i18) makelist (float (f (j)), j, 0, n - 1);
(%o18)      [1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0]



## 22.3 Functions for numerical solution of equations

Function: horner

          horner (<expr>, <x>)
horner (<expr>)
Returns a rearranged representation of <expr> as in Horner's rule,
using <x> as the main variable if it is specified.  x' may be
omitted in which case the main variable of the canonical rational
expression form of <expr> is used.

horner' sometimes improves stability if expr' is to be
numerically evaluated.  It is also useful if Maxima is used to
generate programs to be run in Fortran.  See also stringout'.

(%i1) expr: 1e-155*x^2 - 5.5*x + 5.2e155;
2
(%o1)             1.e-155 x  - 5.5 x + 5.2e+155
(%i2) expr2: horner (%, x), keepfloat: true;
(%o2)         1.0 ((1.e-155 x - 5.5) x + 5.2e+155)
(%i3) ev (expr, x=1e155);
Maxima encountered a Lisp error:

arithmetic error FLOATING-POINT-OVERFLOW signalled

Automatically continuing.
To enable the Lisp debugger set *debugger-hook* to nil.
(%i4) ev (expr2, x=1e155);
(%o4)                 7.00000000000001e+154


Function: find_root (<expr>, <x>, <a>, <b>, [<abserr>, <relerr>])

Function: find_root (<f>, <a>, <b>, [<abserr>, <relerr>])

Function: bf_find_root (<expr>, <x>, <a>, <b>, [<abserr>, <relerr>])

Function: bf_find_root (<f>, <a>, <b>, [<abserr>, <relerr>])

Option variable: find_root_error

Option variable: find_root_abs

Option variable: find_root_rel

     Finds a root of the expression <expr> or the function <f> over the
closed interval [<a>, <b>].  The expression <expr> may be an
equation, in which case find_root' seeks a root of lhs(<expr>) -
rhs(<expr>)'.

Given that Maxima can evaluate <expr> or <f> over [<a>, <b>] and
that <expr> or <f> is continuous, find_root' is guaranteed to
find the root, or one of the roots if there is more than one.

find_root' initially applies binary search.  If the function in
question appears to be smooth enough, find_root' applies linear

bf_find_root' is a bigfloat version of find_root'.  The function
is computed using bigfloat arithmetic and a bigfloat result is
returned.  Otherwise, bf_find_root' is identical to find_root',
and the following description is equally applicable to
bf_find_root'.

The accuracy of find_root' is governed by abserr' and relerr',
which are optional keyword arguments to find_root'.  These
keyword arguments take the form key=val'.  The keyword arguments
are

abserr'
Desired absolute error of function value at root.  Default is
find_root_abs'.

relerr'
Desired relative error of root.  Default is find_root_rel'.

find_root' stops when the function in question evaluates to
something less than or equal to abserr', or if successive
approximants <x_0>, <x_1> differ by no more than relerr *
max(abs(x_0), abs(x_1))'.  The default values of find_root_abs'
and find_root_rel' are both zero.

find_root' expects the function in question to have a different
sign at the endpoints of the search interval.  When the function
evaluates to a number at both endpoints and these numbers have the
same sign, the behavior of find_root' is governed by
find_root_error'.  When find_root_error' is true', find_root'
prints an error message.  Otherwise find_root' returns the value
of find_root_error'.  The default value of find_root_error' is
true'.

If <f> evaluates to something other than a number at any step in
the search algorithm, find_root' returns a partially-evaluated
find_root' expression.

The order of <a> and <b> is ignored; the region in which a root is
sought is [min(<a>, <b>), max(<a>, <b>)].

Examples:

(%i1) f(x) := sin(x) - x/2;
x
(%o1)                  f(x) := sin(x) - -
2
(%i2) find_root (sin(x) - x/2, x, 0.1, %pi);
(%o2)                   1.895494267033981
(%i3) find_root (sin(x) = x/2, x, 0.1, %pi);
(%o3)                   1.895494267033981
(%i4) find_root (f(x), x, 0.1, %pi);
(%o4)                   1.895494267033981
(%i5) find_root (f, 0.1, %pi);
(%o5)                   1.895494267033981
(%i6) find_root (exp(x) = y, x, 0, 100);
x
(%o6)           find_root(%e  = y, x, 0.0, 100.0)
(%i7) find_root (exp(x) = y, x, 0, 100), y = 10;
(%o7)                   2.302585092994046
(%i8) log (10.0);
(%o8)                   2.302585092994046
(%i9) fpprec:32;
(%o9)                           32
(%i10) bf_find_root (exp(x) = y, x, 0, 100), y = 10;
(%o10)                  2.3025850929940456840179914546844b0
(%i11) log(10b0);
(%o11)                  2.3025850929940456840179914546844b0


Function: newton (<expr>, <x>, <x_0>, <eps>)

     Returns an approximate solution of <expr> = 0' by Newton's method,
considering <expr> to be a function of one variable, <x>.  The
search begins with <x> = <x_0>' and proceeds until abs(<expr>) <
<eps>' (with <expr> evaluated at the current value of <x>).

newton' allows undefined variables to appear in <expr>, so long
as the termination test abs(<expr>) < <eps>' evaluates to true'
or false'.  Thus it is not necessary that <expr> evaluate to a
number.

load(newton1)' loads this function.

See also realroots', allroots', find_root', and mnewton'.

Examples:

(%o1)  /maxima/share/numeric/newton1.mac
(%i2) newton (cos (u), u, 1, 1/100);
(%o2)                   1.570675277161251
(%i3) ev (cos (u), u = %);
(%o3)                 1.2104963335033529e-4
(%i4) assume (a > 0);
(%o4)                        [a > 0]
(%i5) newton (x^2 - a^2, x, a/2, a^2/100);
(%o5)                  1.00030487804878 a
(%i6) ev (x^2 - a^2, x = %);
2
(%o6)                6.098490481853958e-4 a



## 22.4 Introduction to numerical solution of differential equations

The Ordinary Differential Equations (ODE) solved by the functions in
this section should have the form,
dy
-- = F(x,y)
dx
which is a first-order ODE. Higher order differential equations of
order <n> must be written as a system of <n> first-order equations of
that kind. For instance, a second-order ODE should be written as a
system of two equations
dx               dy
-- = G(x,y,t)    -- = F(x,y,t)
dt               dt

The first argument in the functions will be a list with the
expressions on the right-side of the ODE's. The variables whose
derivatives are represented by those expressions should be given in a
second list. In the case above those variables are <x> and <y>. The
independent variable, <t> in the examples above, might be given in a
separated option. If the expressions given do not depend on that
independent variable, the system is called autonomous.


## 22.5 Functions for numerical solution of differential equations

Function: plotdf

          plotdf (<dydx>, options...)
plotdf (<dvdu>, [<u>,<v>], options...)
plotdf ([<dxdt>,c<dydt>], options...)
plotdf ([<dudt>,c<dvdt>], [<u>,c<v>], options...)
The function plotdf' creates a two-dimensional plot of the
direction field (also called slope field) for a first-order
Ordinary Differential Equation (ODE) or a system of two autonomous
first-order ODE's.

Plotdf requires Xmaxima, even if its run from a Maxima session in
a console, since the plot will be created by the Tk scripts in
Xmaxima.  If Xmaxima is not installed plotdf will not work.

<dydx>, <dxdt> and <dydt> are expressions that depend on <x> and
<y>. <dvdu>, <dudt> and <dvdt> are expressions that depend on <u>
and <v>. In addition to those two variables, the expressions can
also depend on a set of parameters, with numerical values given
with the parameters' option (the option syntax is given below),
or with a range of allowed values specified by a <sliders> option.

Several other options can be given within the command, or selected
in the menu. Integral curves can be obtained by clicking on the
plot, or with the option trajectory_at'. The direction of the
integration can be controlled with the direction' option, which
can have values of _forward_, _backward_ or _both_. The number of
integration steps is given by nsteps'; at each integration step
the time increment will be adjusted automatically to produce
displacements much smaller than the size of the plot window. The
numerical method used is 4th order Runge-Kutta with variable time
steps.

The menu bar of the plot window has the following seven icons:

An X. Can be used to close the plot window.

A wrench and a screwdriver. Opens the configuration menu with
several fields that show the ODE(s) in use and various other
settings. If a pair of coordinates are entered in the field
_Trajectory at_ and the <enter> key is pressed, a new integral

Two arrows following a circle. Replots the direction field with the
new settings defined in the configuration menu and replots only
the last integral curve that was previously plotted.

Hard disk drive with an arrow. Used to save a copy of the plot, in
Postscript format, in the file specified in a field of the box
that appears when that icon is clicked.

Magnifying glass with a plus sign. Zooms in the plot.

Magnifying glass with a minus sign. Zooms out the plot. The plot
can be displaced by holding down the right mouse button while the
mouse is moved.

Icon of a plot. Opens another window with a plot of the two
variables in terms of time, for the last integral curve that was
plotted.

Plot options:

Options can also be given within the plotdf' itself, each one
being a list of two or more elements. The first element in each
option is the name of the option, and the remainder is the value
or values assigned to the option.

The options which are recognized by plotdf' are the following:

* "nsteps" defines the number of steps that will be used for the
independent variable, to compute an integral curve. The
default value is 100.

* "direction" defines the direction of the independent variable
that will be followed to compute an integral curve. Possible
values are forward', to make the independent variable
increase nsteps' times, with increments tstep', backward',
to make the independent variable decrease, or both' that
will lead to an integral curve that extends nsteps' forward,
and nsteps' backward. The keywords right' and left' can be
used as synonyms for forward' and backward'.  The default
value is both'.

* "tinitial" defines the initial value of variable <t> used to
compute integral curves. Since the differential equations are
autonomous, that setting will only appear in the plot of the
curves as functions of <t>.  The default value is 0.

* "versus_t" is used to create a second plot window, with a
plot of an integral curve, as two functions <x>, <y>, of the
independent variable <t>. If versus_t' is given any value
different from 0, the second plot window will be displayed.
The second plot window includes another menu, similar to the
menu of the main plot window.  The default value is 0.

* "trajectory_at" defines the coordinates <xinitial> and
<yinitial> for the starting point of an integral curve.  The
option is empty by default.

* "parameters" defines a list of parameters, and their
numerical values, used in the definition of the differential
equations. The name and values of the parameters must be
given in a string with a comma-separated sequence of pairs
name=value'.

* "sliders" defines a list of parameters that will be changed
interactively using slider buttons, and the range of
variation of those parameters. The names and ranges of the
parameters must be given in a string with a comma-separated
sequence of elements name=min:max'

* "xfun" defines a string with semi-colon-separated sequence of
functions of <x> to be displayed, on top of the direction
field.  Those functions will be parsed by Tcl and not by
Maxima.

* "x" should be followed by two numbers, which will set up the
minimum and maximum values shown on the horizontal axis. If
the variable on the horizontal axis is not <x>, then this
option should have the name of the variable on the horizontal
axis.  The default horizontal range is from -10 to 10.

* "y" should be followed by two numbers, which will set up the
minimum and maximum values shown on the vertical axis. If the
variable on the vertical axis is not <y>, then this option
should have the name of the variable on the vertical axis.
The default vertical range is from -10 to 10.

* "xaxislabel" will be used to identify the horizontal axis.
Its default value is the name of the first state variable.

* "yaxislabel" will be used to identify the vertical axis. Its
default value is the name of the second state variable.


Function: ploteq (<exp>, ...options...)

     Plots equipotential curves for <exp>, which should be an expression
depending on two variables. The curves are obtained by integrating
the differential equation that define the orthogonal trajectories
to the solutions of the autonomous system obtained from the
gradient of the expression given.  The plot can also show the
integral curves for that gradient system (option fieldlines).

This program also requires Xmaxima, even if its run from a Maxima
session in a console, since the plot will be created by the Tk
scripts in Xmaxima.  By default, the plot region will be empty
until the user clicks in a point (or gives its coordinate with in
the set-up menu or via the trajectory_at option).

Most options accepted by plotdf can also be used for ploteq and
the plot interface is the same that was described in plotdf.

Example:

(%i1) V: 900/((x+1)^2+y^2)^(1/2)-900/((x-1)^2+y^2)^(1/2)$(%i2) ploteq(V,[x,-2,2],[y,-2,2],[fieldlines,"blue"])$

Clicking on a point will plot the equipotential curve that passes
by that point (in red) and the orthogonal trajectory (in blue).


Function: rk

          rk (<ODE>, <var>, <initial>, <domain>)
rk ([<ODE1>, ..., <ODEm>], [<v1>, ..., <vm>], [<init1>, ...,
<initm>], <domain>)
The first form solves numerically one first-order ordinary
differential equation, and the second form solves a system of m of
those equations, using the 4th order Runge-Kutta method. <var>
represents the dependent variable. <ODE> must be an expression
that depends only on the independent and dependent variables and
defines the derivative of the dependent variable with respect to
the independent variable.

The independent variable is specified with domain', which must be
a list of four elements as, for instance:
[t, 0, 10, 0.1]
the first element of the list identifies the independent variable,
the second and third elements are the initial and final values for
that variable, and the last element sets the increments that
should be used within that interval.

If <m> equations are going to be solved, there should be <m>
dependent variables <v1>, <v2>, ..., <vm>. The initial values for
those variables will be <init1>, <init2>, ..., <initm>.  There
will still be just one independent variable defined by domain',
as in the previous case. <ODE1>, ..., <ODEm> are the expressions
that define the derivatives of each dependent variable in terms of
the independent variable. The only variables that may appear in
those expressions are the independent variable and any of the
dependent variables. It is important to give the derivatives
<ODE1>, ..., <ODEm> in the list in exactly the same order used for
the dependent variables; for instance, the third element in the
list will be interpreted as the derivative of the third dependent
variable.

The program will try to integrate the equations from the initial
value of the independent variable until its last value, using
constant increments. If at some step one of the dependent
variables takes an absolute value too large, the integration will
be interrupted at that point. The result will be a list with as
many elements as the number of iterations made. Each element in
the results list is itself another list with <m>+1 elements: the
value of the independent variable, followed by the values of the
dependent variables corresponding to that point.

To solve numerically the differential equation

dx/dt = t - x^2

With initial value x(t=0) = 1, in the interval of t from 0 to 8
and with increments of 0.1 for t, use:

(%i1) results: rk(t-x^2,x,1,[t,0,8,0.1])$(%i2) plot2d ([discrete, results])$

the results will be saved in the list results' and the plot will
show the solution obtained, with <t> on the horizontal axis and
<x> on the vertical axis.

To solve numerically the system:

dx/dt = 4-x^2-4*y^2     dy/dt = y^2-x^2+1

for t between 0 and 4, and with values of -1.25 and 0.75 for x and
y at t=0:

(%i1) sol: rk([4-x^2-4*y^2,y^2-x^2+1],[x,y],[-1.25,0.75],[t,0,4,0.02])$(%i2) plot2d ([discrete,makelist([p,p],p,sol)], [xlabel,"t"],[ylabel,"y"])$

The plot will show the solution for variable <y> as a function of
<t>.



## 23 Matrices and Linear Algebra


Introduction to Matrices and Linear Algebra
Functions and Variables for Matrices and Linear Algebra



* Dot::
* Vectors::
* eigen::


## 23.2 Functions and Variables for Matrices and Linear Algebra

Function: addcol (<M>, <list_1>, ..., <list_n>)

     Appends the column(s) given by the one or more lists (or matrices)
onto the matrix <M>.


Function: addrow (<M>, <list_1>, ..., <list_n>)

     Appends the row(s) given by the one or more lists (or matrices)
onto the matrix <M>.


Function: adjoint (<M>)

     Returns the adjoint of the matrix <M>.  The adjoint matrix is the
transpose of the matrix of cofactors of <M>.


Function: augcoefmatrix ([<eqn_1>, ..., <eqn_m>], [<x_1>, ..., <x_n>])

     Returns the augmented coefficient matrix for the variables <x_1>,
..., <x_n> of the system of linear equations <eqn_1>, ...,
<eqn_m>.  This is the coefficient matrix with a column adjoined
for the constant terms in each equation (i.e., those terms not
dependent upon <x_1>, ..., <x_n>).

(%i1) m: [2*x - (a - 1)*y = 5*b, c + b*y + a*x = 0]$(%i2) augcoefmatrix (m, [x, y]); [ 2 1 - a - 5 b ] (%o2) [ ] [ a b c ]  Function: cauchy_matrix   cauchy_matrix ([<x_1>, <x_2>, ..., <x_m>], [<y_1>, <y_2>, ..., <y_n>]) cauchy_matrix ([<x_1>, <x_2>, ..., <x_n>]) Returns a n' by <m> Cauchy matrix with the elements <a[i,j]> = 1/(<x_i>+<y_i>). The second argument of cauchy_matrix' is optional. For this case the elements of the Cauchy matrix are <a[i,j]> = 1/(<x_i>+<x_j>). Remark: In the literature the Cauchy matrix can be found defined in two forms. A second definition is <a[i,j]> = 1/(<x_i>-<y_i>). Examples: (%i1) cauchy_matrix([x1,x2],[y1,y2]); [ 1 1 ] [ ------- ------- ] [ y1 + x1 y2 + x1 ] (%o1) [ ] [ 1 1 ] [ ------- ------- ] [ y1 + x2 y2 + x2 ] (%i2) cauchy_matrix([x1,x2]); [ 1 1 ] [ ---- ------- ] [ 2 x1 x2 + x1 ] (%o2) [ ] [ 1 1 ] [ ------- ---- ] [ x2 + x1 2 x2 ]  Function: charpoly (<M>, <x>)   Returns the characteristic polynomial for the matrix <M> with respect to variable <x>. That is, determinant (<M> - diagmatrix (length (<M>), <x>))'. (%i1) a: matrix ([3, 1], [2, 4]); [ 3 1 ] (%o1) [ ] [ 2 4 ] (%i2) expand (charpoly (a, lambda)); 2 (%o2) lambda - 7 lambda + 10 (%i3) (programmode: true, solve (%)); (%o3) [lambda = 5, lambda = 2] (%i4) matrix ([x1], [x2]); [ x1 ] (%o4) [ ] [ x2 ] (%i5) ev (a . % - lambda*%, %th(2)); [ x2 - 2 x1 ] (%o5) [ ] [ 2 x1 - x2 ] (%i6) %[1, 1] = 0; (%o6) x2 - 2 x1 = 0 (%i7) x2^2 + x1^2 = 1; 2 2 (%o7) x2 + x1 = 1 (%i8) solve ([%th(2), %], [x1, x2]); 1 2 (%o8) [[x1 = - -------, x2 = - -------], sqrt(5) sqrt(5) 1 2 [x1 = -------, x2 = -------]] sqrt(5) sqrt(5)  Function: coefmatrix ([<eqn_1>, ..., <eqn_m>], [<x_1>, ..., <x_n>])   Returns the coefficient matrix for the variables <x_1>, ..., <x_n> of the system of linear equations <eqn_1>, ..., <eqn_m>. (%i1) coefmatrix([2*x-(a-1)*y+5*b = 0, b*y+a*x = 3], [x,y]); [ 2 1 - a ] (%o1) [ ] [ a b ]  Function: col (<M>, <i>)   Returns the <i>'th column of the matrix <M>. The return value is a matrix.  Function: columnvector (<L>)  Function: covect (<L>)   Returns a matrix of one column and length (<L>)' rows, containing the elements of the list <L>. covect' is a synonym for columnvector'. load ("eigen")' loads this function. This is useful if you want to use parts of the outputs of the functions in this package in matrix calculations. Example: (%i1) load ("eigen")$
Warning - you are redefining the Macsyma function eigenvalues
Warning - you are redefining the Macsyma function eigenvectors
(%i2) columnvector ([aa, bb, cc, dd]);
[ aa ]
[    ]
[ bb ]
(%o2)                        [    ]
[ cc ]
[    ]
[ dd ]


Function: copymatrix (<M>)

     Returns a copy of the matrix <M>.  This is the only way to make a
copy aside from copying <M> element by element.

Note that an assignment of one matrix to another, as in m2: m1',
does not copy m1'.  An assignment m2 [i,j]: x' or setelmx(x, i,
j, m2)' also modifies m1 [i,j]'.  Creating a copy with
copymatrix' and then using assignment creates a separate,
modified copy.


Function: determinant (<M>)

     Computes the determinant of <M> by a method similar to Gaussian
elimination.

The form of the result depends upon the setting of the switch
ratmx'.

There is a special routine for computing sparse determinants which
is called when the switches ratmx' and sparse' are both true'.


Option variable: detout

     Default value: false'

When detout' is true', the determinant of a matrix whose inverse
is computed is factored out of the inverse.

For this switch to have an effect doallmxops' and doscmxops'
should be false' (see their descriptions).  Alternatively this
switch can be given to ev' which causes the other two to be set
correctly.

Example:

(%i1) m: matrix ([a, b], [c, d]);
[ a  b ]
(%o1)                       [      ]
[ c  d ]
(%i2) detout: true$(%i3) doallmxops: false$
(%i4) doscmxops: false$(%i5) invert (m); [ d - b ] [ ] [ - c a ] (%o5) ------------ a d - b c  Function: diagmatrix (<n>, <x>)   Returns a diagonal matrix of size <n> by <n> with the diagonal elements all equal to <x>. diagmatrix (<n>, 1)' returns an identity matrix (same as ident (<n>)'). <n> must evaluate to an integer, otherwise diagmatrix' complains with an error message. <x> can be any kind of expression, including another matrix. If <x> is a matrix, it is not copied; all diagonal elements refer to the same instance, <x>.  Option variable: doallmxops   Default value: true' When doallmxops' is true', all operations relating to matrices are carried out. When it is false' then the setting of the individual dot' switches govern which operations are performed.  Option variable: domxexpt   Default value: true' When domxexpt' is true', a matrix exponential, exp (<M>)' where <M> is a matrix, is interpreted as a matrix with element [i,j]' equal to exp (m[i,j])'. Otherwise exp (<M>)' evaluates to exp (<ev(M)>)'. domxexpt' affects all expressions of the form <base>^<power>' where <base> is an expression assumed scalar or constant, and <power> is a list or matrix. Example: (%i1) m: matrix ([1, %i], [a+b, %pi]); [ 1 %i ] (%o1) [ ] [ b + a %pi ] (%i2) domxexpt: false$
(%i3) (1 - c)^m;
[   1    %i  ]
[            ]
[ b + a  %pi ]
(%o3)                 (1 - c)
(%i4) domxexpt: true$(%i5) (1 - c)^m; [ %i ] [ 1 - c (1 - c) ] (%o5) [ ] [ b + a %pi ] [ (1 - c) (1 - c) ]  Option variable: domxmxops   Default value: true' When domxmxops' is true', all matrix-matrix or matrix-list operations are carried out (but not scalar-matrix operations); if this switch is false' such operations are not carried out.  Option variable: domxnctimes   Default value: false' When domxnctimes' is true', non-commutative products of matrices are carried out.  Option variable: dontfactor   Default value: []' dontfactor' may be set to a list of variables with respect to which factoring is not to occur. (The list is initially empty.) Factoring also will not take place with respect to any variables which are less important, according the variable ordering assumed for canonical rational expression (CRE) form, than those on the dontfactor' list.  Option variable: doscmxops   Default value: false' When doscmxops' is true', scalar-matrix operations are carried out.  Option variable: doscmxplus   Default value: false' When doscmxplus' is true', scalar-matrix operations yield a matrix result. This switch is not subsumed under doallmxops'.  Option variable: dot0nscsimp   Default value: true' When dot0nscsimp' is true', a non-commutative product of zero and a nonscalar term is simplified to a commutative product.  Option variable: dot0simp   Default value: true' When dot0simp' is true', a non-commutative product of zero and a scalar term is simplified to a commutative product.  Option variable: dot1simp   Default value: true' When dot1simp' is true', a non-commutative product of one and another term is simplified to a commutative product.  Option variable: dotassoc   Default value: true' When dotassoc' is true', an expression (A.B).C' simplifies to A.(B.C)'.  Option variable: dotconstrules   Default value: true' When dotconstrules' is true', a non-commutative product of a constant and another term is simplified to a commutative product. Turning on this flag effectively turns on dot0simp', dot0nscsimp', and dot1simp' as well.  Option variable: dotdistrib   Default value: false' When dotdistrib' is true', an expression A.(B + C)' simplifies to A.B + A.C'.  Option variable: dotexptsimp   Default value: true' When dotexptsimp' is true', an expression A.A' simplifies to A^^2'.  Option variable: dotident   Default value: 1 dotident' is the value returned by X^^0'.  Option variable: dotscrules   Default value: false' When dotscrules' is true', an expression A.SC' or SC.A' simplifies to SC*A' and A.(SC*B)' simplifies to SC*(A.B)'.  Function: echelon (<M>)   Returns the echelon form of the matrix <M>, as produced by Gaussian elimination. The echelon form is computed from <M> by elementary row operations such that the first non-zero element in each row in the resulting matrix is one and the column elements under the first one in each row are all zero. triangularize' also carries out Gaussian elimination, but it does not normalize the leading non-zero element in each row. lu_factor' and cholesky' are other functions which yield triangularized matrices. (%i1) M: matrix ([3, 7, aa, bb], [-1, 8, 5, 2], [9, 2, 11, 4]); [ 3 7 aa bb ] [ ] (%o1) [ - 1 8 5 2 ] [ ] [ 9 2 11 4 ] (%i2) echelon (M); [ 1 - 8 - 5 - 2 ] [ ] [ 28 11 ] [ 0 1 -- -- ] (%o2) [ 37 37 ] [ ] [ 37 bb - 119 ] [ 0 0 1 ----------- ] [ 37 aa - 313 ]  Function: eigenvalues (<M>)  Function: eivals (<M>)   Returns a list of two lists containing the eigenvalues of the matrix <M>. The first sublist of the return value is the list of eigenvalues of the matrix, and the second sublist is the list of the multiplicities of the eigenvalues in the corresponding order. eivals' is a synonym for eigenvalues'. eigenvalues' calls the function solve' to find the roots of the characteristic polynomial of the matrix. Sometimes solve' may not be able to find the roots of the polynomial; in that case some other functions in this package (except innerproduct', unitvector', columnvector' and gramschmidt') will not work. In some cases the eigenvalues found by solve' may be complicated expressions. (This may happen when solve' returns a not-so-obviously real expression for an eigenvalue which is known to be real.) It may be possible to simplify the eigenvalues using some other functions. The package eigen.mac' is loaded automatically when eigenvalues' or eigenvectors' is referenced. If eigen.mac' is not already loaded, load ("eigen")' loads it. After loading, all functions and variables in the package are available.  Function: eigenvectors (<M>)  Function: eivects (<M>)   Computes eigenvectors of the matrix <M>. The return value is a list of two elements. The first is a list of the eigenvalues of <M> and a list of the multiplicities of the eigenvalues. The second is a list of lists of eigenvectors. There is one list of eigenvectors for each eigenvalue. There may be one or more eigenvectors in each list. eivects' is a synonym for eigenvectors'. The package eigen.mac' is loaded automatically when eigenvalues' or eigenvectors' is referenced. If eigen.mac' is not already loaded, load ("eigen")' loads it. After loading, all functions and variables in the package are available. The flags that affect this function are: nondiagonalizable' is set to true' or false' depending on whether the matrix is nondiagonalizable or diagonalizable after eigenvectors' returns. hermitianmatrix' when true', causes the degenerate eigenvectors of the Hermitian matrix to be orthogonalized using the Gram-Schmidt algorithm. knowneigvals' when true' causes the eigen' package to assume the eigenvalues of the matrix are known to the user and stored under the global name listeigvals'. listeigvals' should be set to a list similar to the output eigenvalues'. The function algsys' is used here to solve for the eigenvectors. Sometimes if the eigenvalues are messy, algsys' may not be able to find a solution. In some cases, it may be possible to simplify the eigenvalues by first finding them using eigenvalues' command and then using other functions to reduce them to something simpler. Following simplification, eigenvectors' can be called again with the knowneigvals' flag set to true'. See also eigenvalues'. Examples: A matrix which has just one eigenvector per eigenvalue. (%i1) M1 : matrix ([11, -1], [1, 7]); [ 11 - 1 ] (%o1) [ ] [ 1 7 ] (%i2) [vals, vecs] : eigenvectors (M1); (%o2) [[[9 - sqrt(3), sqrt(3) + 9], [1, 1]], [[[1, sqrt(3) + 2]], [[1, 2 - sqrt(3)]]]] (%i3) for i thru length (vals) do disp (val[i] = vals[i], mult[i] = vals[i], vec[i] = vecs[i]); val = 9 - sqrt(3) 1 mult = 1 1 vec = [[1, sqrt(3) + 2]] 1 val = sqrt(3) + 9 2 mult = 1 2 vec = [[1, 2 - sqrt(3)]] 2 (%o3) done A matrix which has two eigenvectors for one eigenvalue (namely 2). (%i1) M1 : matrix ([0, 1, 0, 0], [0, 0, 0, 0], [0, 0, 2, 0], [0, 0, 0, 2]); [ 0 1 0 0 ] [ ] [ 0 0 0 0 ] (%o1) [ ] [ 0 0 2 0 ] [ ] [ 0 0 0 2 ] (%i2) [vals, vecs] : eigenvectors (M1); (%o2) [[[0, 2], [2, 2]], [[[1, 0, 0, 0]], [[0, 0, 1, 0], [0, 0, 0, 1]]]] (%i3) for i thru length (vals) do disp (val[i] = vals[i], mult[i] = vals[i], vec[i] = vecs[i]); val = 0 1 mult = 2 1 vec = [[1, 0, 0, 0]] 1 val = 2 2 mult = 2 2 vec = [[0, 0, 1, 0], [0, 0, 0, 1]] 2 (%o3) done  Function: ematrix (<m>, <n>, <x>, <i>, <j>)   Returns an <m> by <n> matrix, all elements of which are zero except for the [<i>, <j>]' element which is <x>.  Function: entermatrix (<m>, <n>)   Returns an <m> by <n> matrix, reading the elements interactively. If <n> is equal to <m>, Maxima prompts for the type of the matrix (diagonal, symmetric, antisymmetric, or general) and for each element. Each response is terminated by a semicolon ;' or dollar sign $'.

If <n> is not equal to <m>, Maxima prompts for each element.

The elements may be any expressions, which are evaluated.
entermatrix' evaluates its arguments.

(%i1) n: 3$(%i2) m: entermatrix (n, n)$

Is the matrix  1. Diagonal  2. Symmetric  3. Antisymmetric
4. General
Answer 1, 2, 3 or 4 :
1$Row 1 Column 1: (a+b)^n$
Row 2 Column 2:
(a+b)^(n+1)$Row 3 Column 3: (a+b)^(n+2)$

Matrix entered.
(%i3) m;
[        3                     ]
[ (b + a)      0         0     ]
[                              ]
(%o3)           [                  4           ]
[    0      (b + a)      0     ]
[                              ]
[                            5 ]
[    0         0      (b + a)  ]


Function: genmatrix

          genmatrix (<a>, <i_2>, <j_2>, <i_1>, <j_1>)
genmatrix (<a>, <i_2>, <j_2>, <i_1>)
genmatrix (<a>, <i_2>, <j_2>)
Returns a matrix generated from <a>, taking element <a>[<i_1>,
<j_1>]' as the upper-left element and <a>[<i_2>, <j_2>]' as the
lower-right element of the matrix.  Here <a> is a declared array
(created by array' but not by make_array') or an undeclared
array, or an array function, or a lambda expression of two
arguments.  (An array function is created like other functions
with :=' or define', but arguments are enclosed in square

If <j_1> is omitted, it is assumed equal to <i_1>.  If both <j_1>
and <i_1> are omitted, both are assumed equal to 1.

If a selected element i,j' of the array is undefined, the matrix
will contain a symbolic element <a>[i,j]'.

Examples:

(%i1) h [i, j] := 1 / (i + j - 1);
1
(%o1)                  h     := ---------
i, j    i + j - 1
(%i2) genmatrix (h, 3, 3);
[    1  1 ]
[ 1  -  - ]
[    2  3 ]
[         ]
[ 1  1  1 ]
(%o2)                      [ -  -  - ]
[ 2  3  4 ]
[         ]
[ 1  1  1 ]
[ -  -  - ]
[ 3  4  5 ]
(%i3) array (a, fixnum, 2, 2);
(%o3)                           a
(%i4) a [1, 1] : %e;
(%o4)                          %e
(%i5) a [2, 2] : %pi;
(%o5)                          %pi
(%i6) genmatrix (a, 2, 2);
[ %e   0  ]
(%o6)                      [         ]
[ 0   %pi ]
(%i7) genmatrix (lambda ([i, j], j - i), 3, 3);
[  0    1   2 ]
[             ]
(%o7)                    [ - 1   0   1 ]
[             ]
[ - 2  - 1  0 ]
(%i8) genmatrix (B, 2, 2);
[ B      B     ]
[  1, 1   1, 2 ]
(%o8)                   [              ]
[ B      B     ]
[  2, 1   2, 2 ]


Function: gramschmidt

          gramschmidt (<x>)
gramschmidt (<x>, <F>)
Carries out the Gram-Schmidt orthogonalization algorithm on <x>,
which is either a matrix or a list of lists.  <x> is not modified
by gramschmidt'.  The inner product employed by gramschmidt' is
<F>, if present, otherwise the inner product is the function
innerproduct'.

If <x> is a matrix, the algorithm is applied to the rows of <x>.
If <x> is a list of lists, the algorithm is applied to the
sublists, which must have equal numbers of elements.  In either
case, the return value is a list of lists, the sublists of which
are orthogonal and span the same space as <x>.  If the dimension
of the span of <x> is less than the number of rows or sublists,
some sublists of the return value are zero.

factor' is called at each stage of the algorithm to simplify
intermediate results.  As a consequence, the return value may
contain factored integers.

load(eigen)' loads this function.

Example:

Gram-Schmidt algorithm using default inner product function.

(%i1) load (eigen)$(%i2) x: matrix ([1, 2, 3], [9, 18, 30], [12, 48, 60]); [ 1 2 3 ] [ ] (%o2) [ 9 18 30 ] [ ] [ 12 48 60 ] (%i3) y: gramschmidt (x); 2 2 4 3 3 3 3 5 2 3 2 3 (%o3) [[1, 2, 3], [- ---, - --, ---], [- ----, ----, 0]] 2 7 7 2 7 5 5 (%i4) map (innerproduct, [y, y, y], [y, y, y]); (%o4) [0, 0, 0] Gram-Schmidt algorithm using a specified inner product function. (%i1) load (eigen)$
(%i2) ip (f, g) := integrate (f * g, u, a, b);
(%o2)          ip(f, g) := integrate(f g, u, a, b)
(%i3) y : gramschmidt([1, sin(u), cos(u)], ip), a= -%pi/2, b=%pi/2;
%pi cos(u) - 2
(%o3)              [1, sin(u), --------------]
%pi
(%i4) map (ip, [y, y, y], [y, y, y]),
a= -%pi/2, b=%pi/2;
(%o4)                       [0, 0, 0]


Function: ident (<n>)

     Returns an <n> by <n> identity matrix.


Function: innerproduct (<x>, <y>)

Function: inprod (<x>, <y>)

     Returns the inner product (also called the scalar product or dot
product) of <x> and <y>, which are lists of equal length, or both
1-column or 1-row matrices of equal length.  The return value is
conjugate (x) . y', where .' is the noncommutative
multiplication operator.

inprod' is a synonym for innerproduct'.


Function: invert_by_adjoint (<M>)

     Returns the inverse of the matrix <M>.  The inverse is computed by

invert_by_adjoint' honors the ratmx' and detout' flags, the
same as invert'.


Function: invert (<M>)

     Returns the inverse of the matrix <M>.  The inverse is computed
via the LU decomposition.

When ratmx' is true', elements of <M> are converted to canonical
rational expressions (CRE), and the elements of the return value
are also CRE.

When ratmx' is false', elements of <M> are not converted to a
common representation.  In particular, float and bigfloat elements
are not converted to rationals.

When detout' is true', the determinant is factored out of the
inverse.  The global flags doallmxops' and doscmxops' must be
false' to prevent the determinant from being absorbed into the
inverse.  xthru' can multiply the determinant into the inverse.

invert' does not apply any simplifications to the elements of the
inverse apart from the default arithmetic simplifications.
ratsimp' and expand' can apply additional simplifications.  In
particular, when <M> has polynomial elements,
expand(invert(<M>))' might be preferable.

invert(<M>)' is equivalent to <M>^^-1'.


Function: list_matrix_entries (<M>)

     Returns a list containing the elements of the matrix <M>.

Example:

(%i1) list_matrix_entries(matrix([a,b],[c,d]));
(%o1)                     [a, b, c, d]


Option variable: lmxchar

     Default value: ['

lmxchar' is the character displayed as the left delimiter of a
matrix.  See also rmxchar'.

Example:

(%i1) lmxchar: "|"$(%i2) matrix ([a, b, c], [d, e, f], [g, h, i]); | a b c ] | ] (%o2) | d e f ] | ] | g h i ]  Function: matrix (<row_1>, ..., <row_n>)   Returns a rectangular matrix which has the rows <row_1>, ..., <row_n>. Each row is a list of expressions. All rows must be the same length. The operations +' (addition), -' (subtraction), *' (multiplication), and /' (division), are carried out element by element when the operands are two matrices, a scalar and a matrix, or a matrix and a scalar. The operation ^' (exponentiation, equivalently **') is carried out element by element if the operands are a scalar and a matrix or a matrix and a scalar, but not if the operands are two matrices. All operations are normally carried out in full, including .' (noncommutative multiplication). Matrix multiplication is represented by the noncommutative multiplication operator .'. The corresponding noncommutative exponentiation operator is ^^'. For a matrix <A>', <A>.<A> = <A>^^2' and <A>^^-1' is the inverse of <A>, if it exists. <A>^^-1' is equivalent to invert(<A>)'. There are switches for controlling simplification of expressions involving dot and matrix-list operations. These are doallmxops', domxexpt', domxmxops', doscmxops', and doscmxplus'. There are additional options which are related to matrices. These are: lmxchar', rmxchar', ratmx', listarith', detout', scalarmatrix' and sparse'. There are a number of functions which take matrices as arguments or yield matrices as return values. See eigenvalues', eigenvectors', determinant', charpoly', genmatrix', addcol', addrow', copymatrix', transpose', echelon', and rank'. Examples: * Construction of matrices from lists. (%i1) x: matrix ([17, 3], [-8, 11]); [ 17 3 ] (%o1) [ ] [ - 8 11 ] (%i2) y: matrix ([%pi, %e], [a, b]); [ %pi %e ] (%o2) [ ] [ a b ] * Addition, element by element. (%i3) x + y; [ %pi + 17 %e + 3 ] (%o3) [ ] [ a - 8 b + 11 ] * Subtraction, element by element. (%i4) x - y; [ 17 - %pi 3 - %e ] (%o4) [ ] [ - a - 8 11 - b ] * Multiplication, element by element. (%i5) x * y; [ 17 %pi 3 %e ] (%o5) [ ] [ - 8 a 11 b ] * Division, element by element. (%i6) x / y; [ 17 - 1 ] [ --- 3 %e ] [ %pi ] (%o6) [ ] [ 8 11 ] [ - - -- ] [ a b ] * Matrix to a scalar exponent, element by element. (%i7) x ^ 3; [ 4913 27 ] (%o7) [ ] [ - 512 1331 ] * Scalar base to a matrix exponent, element by element. (%i8) exp(y); [ %pi %e ] [ %e %e ] (%o8) [ ] [ a b ] [ %e %e ] * Matrix base to a matrix exponent. This is not carried out element by element. (%i9) x ^ y; [ %pi %e ] [ ] [ a b ] [ 17 3 ] (%o9) [ ] [ - 8 11 ] * Noncommutative matrix multiplication. (%i10) x . y; [ 3 a + 17 %pi 3 b + 17 %e ] (%o10) [ ] [ 11 a - 8 %pi 11 b - 8 %e ] (%i11) y . x; [ 17 %pi - 8 %e 3 %pi + 11 %e ] (%o11) [ ] [ 17 a - 8 b 11 b + 3 a ] * Noncommutative matrix exponentiation. A scalar base <b> to a matrix power <M> is carried out element by element and so b^^m' is the same as b^m'. (%i12) x ^^ 3; [ 3833 1719 ] (%o12) [ ] [ - 4584 395 ] (%i13) %e ^^ y; [ %pi %e ] [ %e %e ] (%o13) [ ] [ a b ] [ %e %e ] * A matrix raised to a -1 exponent with noncommutative exponentiation is the matrix inverse, if it exists. (%i14) x ^^ -1; [ 11 3 ] [ --- - --- ] [ 211 211 ] (%o14) [ ] [ 8 17 ] [ --- --- ] [ 211 211 ] (%i15) x . (x ^^ -1); [ 1 0 ] (%o15) [ ] [ 0 1 ]  Function: matrixmap (<f>, <M>)   Returns a matrix with element i,j' equal to <f>(<M>[i,j])'. See also map', fullmap', fullmapl', and apply'.  Function: matrixp (<expr>)   Returns true' if <expr> is a matrix, otherwise false'.  Option variable: matrix_element_add   Default value: +' matrix_element_add' is the operation invoked in place of addition in a matrix multiplication. matrix_element_add' can be assigned any n-ary operator (that is, a function which handles any number of arguments). The assigned value may be the name of an operator enclosed in quote marks, the name of a function, or a lambda expression. See also matrix_element_mult' and matrix_element_transpose'. Example: (%i1) matrix_element_add: "*"$
(%i2) matrix_element_mult: "^"$(%i3) aa: matrix ([a, b, c], [d, e, f]); [ a b c ] (%o3) [ ] [ d e f ] (%i4) bb: matrix ([u, v, w], [x, y, z]); [ u v w ] (%o4) [ ] [ x y z ] (%i5) aa . transpose (bb); [ u v w x y z ] [ a b c a b c ] (%o5) [ ] [ u v w x y z ] [ d e f d e f ]  Option variable: matrix_element_mult   Default value: *' matrix_element_mult' is the operation invoked in place of multiplication in a matrix multiplication. matrix_element_mult' can be assigned any binary operator. The assigned value may be the name of an operator enclosed in quote marks, the name of a function, or a lambda expression. The dot operator .' is a useful choice in some contexts. See also matrix_element_add' and matrix_element_transpose'. Example: (%i1) matrix_element_add: lambda ([[x]], sqrt (apply ("+", x)))$
(%i2) matrix_element_mult: lambda ([x, y], (x - y)^2)$(%i3) [a, b, c] . [x, y, z]; 2 2 2 (%o3) sqrt((c - z) + (b - y) + (a - x) ) (%i4) aa: matrix ([a, b, c], [d, e, f]); [ a b c ] (%o4) [ ] [ d e f ] (%i5) bb: matrix ([u, v, w], [x, y, z]); [ u v w ] (%o5) [ ] [ x y z ] (%i6) aa . transpose (bb); [ 2 2 2 ] [ sqrt((c - w) + (b - v) + (a - u) ) ] (%o6) Col 1 = [ ] [ 2 2 2 ] [ sqrt((f - w) + (e - v) + (d - u) ) ] [ 2 2 2 ] [ sqrt((c - z) + (b - y) + (a - x) ) ] Col 2 = [ ] [ 2 2 2 ] [ sqrt((f - z) + (e - y) + (d - x) ) ]  Option variable: matrix_element_transpose   Default value: false' matrix_element_transpose' is the operation applied to each element of a matrix when it is transposed. matrix_element_mult' can be assigned any unary operator. The assigned value may be the name of an operator enclosed in quote marks, the name of a function, or a lambda expression. When matrix_element_transpose' equals transpose', the transpose' function is applied to every element. When matrix_element_transpose' equals nonscalars', the transpose' function is applied to every nonscalar element. If some element is an atom, the nonscalars' option applies transpose' only if the atom is declared nonscalar, while the transpose' option always applies transpose'. The default value, false', means no operation is applied. See also matrix_element_add' and matrix_element_mult'. Examples: (%i1) declare (a, nonscalar)$
(%i2) transpose ([a, b]);
[ transpose(a) ]
(%o2)                   [              ]
[      b       ]
(%i3) matrix_element_transpose: nonscalars$(%i4) transpose ([a, b]); [ transpose(a) ] (%o4) [ ] [ b ] (%i5) matrix_element_transpose: transpose$
(%i6) transpose ([a, b]);
[ transpose(a) ]
(%o6)                   [              ]
[ transpose(b) ]
(%i7) matrix_element_transpose: lambda ([x], realpart(x)
- %i*imagpart(x))$(%i8) m: matrix ([1 + 5*%i, 3 - 2*%i], [7*%i, 11]); [ 5 %i + 1 3 - 2 %i ] (%o8) [ ] [ 7 %i 11 ] (%i9) transpose (m); [ 1 - 5 %i - 7 %i ] (%o9) [ ] [ 2 %i + 3 11 ]  Function: mattrace (<M>)   Returns the trace (that is, the sum of the elements on the main diagonal) of the square matrix <M>. mattrace' is called by ncharpoly', an alternative to Maxima's charpoly'. load ("nchrpl")' loads this function.  Function: minor (<M>, <i>, <j>)   Returns the <i>, <j> minor of the matrix <M>. That is, <M> with row <i> and column <j> removed.  Function: ncharpoly (<M>, <x>)   Returns the characteristic polynomial of the matrix <M> with respect to <x>. This is an alternative to Maxima's charpoly'. ncharpoly' works by computing traces of powers of the given matrix, which are known to be equal to sums of powers of the roots of the characteristic polynomial. From these quantities the symmetric functions of the roots can be calculated, which are nothing more than the coefficients of the characteristic polynomial. charpoly' works by forming the determinant of <x> * ident [n] - a'. Thus ncharpoly' wins, for example, in the case of large dense matrices filled with integers, since it avoids polynomial arithmetic altogether. load ("nchrpl")' loads this file.  Function: newdet (<M>)   Computes the determinant of the matrix <M> by the Johnson-Gentleman tree minor algorithm. newdet' returns the result in CRE form.  Function: permanent (<M>)   Computes the permanent of the matrix <M> by the Johnson-Gentleman tree minor algorithm. A permanent is like a determinant but with no sign changes. permanent' returns the result in CRE form. See also newdet'.  Function: rank (<M>)   Computes the rank of the matrix <M>. That is, the order of the largest non-singular subdeterminant of <M>. <rank> may return the wrong answer if it cannot determine that a matrix element that is equivalent to zero is indeed so.  Option variable: ratmx   Default value: false' When ratmx' is false', determinant and matrix addition, subtraction, and multiplication are performed in the representation of the matrix elements and cause the result of matrix inversion to be left in general representation. When ratmx' is true', the 4 operations mentioned above are performed in CRE form and the result of matrix inverse is in CRE form. Note that this may cause the elements to be expanded (depending on the setting of ratfac') which might not always be desired.  Function: row (<M>, <i>)   Returns the <i>'th row of the matrix <M>. The return value is a matrix.  Option variable: rmxchar   Default value: ]' rmxchar' is the character drawn on the right-hand side of a matrix. See also lmxchar'.  Option variable: scalarmatrixp   Default value: true' When scalarmatrixp' is true', then whenever a 1 x 1 matrix is produced as a result of computing the dot product of matrices it is simplified to a scalar, namely the sole element of the matrix. When scalarmatrixp' is all', then all 1 x 1 matrices are simplified to scalars. When scalarmatrixp' is false', 1 x 1 matrices are not simplified to scalars.  Function: scalefactors (<coordinatetransform>)   Here the argument <coordinatetransform> evaluates to the form [[expression1, expression2, ...], indeterminate1, indeterminat2, ...]', where the variables <indeterminate1>, <indeterminate2>, etc. are the curvilinear coordinate variables and where a set of rectangular Cartesian components is given in terms of the curvilinear coordinates by [expression1, expression2, ...]'. coordinates' is set to the vector [indeterminate1, indeterminate2,...]', and dimension' is set to the length of this vector. SF, SF, ..., SF[DIMENSION] are set to the coordinate scale factors, and sfprod' is set to the product of these scale factors. Initially, coordinates' is [X, Y, Z]', dimension' is 3, and SF=SF=SF=SFPROD=1, corresponding to 3-dimensional rectangular Cartesian coordinates. To expand an expression into physical components in the current coordinate system, there is a function with usage of the form  Function: setelmx (<x>, <i>, <j>, <M>)   Assigns <x> to the (<i>, <j>)'th element of the matrix <M>, and returns the altered matrix. <M> [<i>, <j>]: <x>' has the same effect, but returns <x> instead of <M>.  Function: similaritytransform (<M>)  Function: simtran (<M>)   similaritytransform' computes a similarity transform of the matrix M'. It returns a list which is the output of the uniteigenvectors' command. In addition if the flag nondiagonalizable' is false' two global matrices leftmatrix' and rightmatrix' are computed. These matrices have the property that leftmatrix . <M> . rightmatrix' is a diagonal matrix with the eigenvalues of <M> on the diagonal. If nondiagonalizable' is true' the left and right matrices are not computed. If the flag hermitianmatrix' is true' then leftmatrix' is the complex conjugate of the transpose of rightmatrix'. Otherwise leftmatrix' is the inverse of rightmatrix'. rightmatrix' is the matrix the columns of which are the unit eigenvectors of <M>. The other flags (see eigenvalues' and eigenvectors') have the same effects since similaritytransform' calls the other functions in the package in order to be able to form rightmatrix'. load ("eigen")' loads this function. simtran' is a synonym for similaritytransform'.  Option variable: sparse   Default value: false' When sparse' is true', and if ratmx' is true', then determinant' will use special routines for computing sparse determinants.  Function: submatrix   submatrix (<i_1>, ..., <i_m>, <M>, <j_1>, ..., <j_n>) submatrix (<i_1>, ..., <i_m>, <M>) submatrix (<M>, <j_1>, ..., <j_n>) Returns a new matrix composed of the matrix <M> with rows <i_1>, ..., <i_m> deleted, and columns <j_1>, ..., <j_n> deleted.  Function: transpose (<M>)   Returns the transpose of <M>. If <M> is a matrix, the return value is another matrix <N> such that N[i,j] = M[j,i]'. If <M> is a list, the return value is a matrix <N> of length (m)' rows and 1 column, such that N[i,1] = M[i]'. Otherwise <M> is a symbol, and the return value is a noun expression 'transpose (<M>)'.  Function: triangularize (<M>)   Returns the upper triangular form of the matrix M', as produced by Gaussian elimination. The return value is the same as echelon', except that the leading nonzero coefficient in each row is not normalized to 1. lu_factor' and cholesky' are other functions which yield triangularized matrices. (%i1) M: matrix ([3, 7, aa, bb], [-1, 8, 5, 2], [9, 2, 11, 4]); [ 3 7 aa bb ] [ ] (%o1) [ - 1 8 5 2 ] [ ] [ 9 2 11 4 ] (%i2) triangularize (M); [ - 1 8 5 2 ] [ ] (%o2) [ 0 - 74 - 56 - 22 ] [ ] [ 0 0 626 - 74 aa 238 - 74 bb ]  Function: uniteigenvectors (<M>)  Function: ueivects (<M>)   Computes unit eigenvectors of the matrix <M>. The return value is a list of lists, the first sublist of which is the output of the eigenvalues' command, and the other sublists of which are the unit eigenvectors of the matrix corresponding to those eigenvalues respectively. The flags mentioned in the description of the eigenvectors' command have the same effects in this one as well. When knowneigvects' is true', the eigen' package assumes that the eigenvectors of the matrix are known to the user and are stored under the global name listeigvects'. listeigvects' should be set to a list similar to the output of the eigenvectors' command. If knowneigvects' is set to true' and the list of eigenvectors is given the setting of the flag nondiagonalizable' may not be correct. If that is the case please set it to the correct value. The author assumes that the user knows what he is doing and will not try to diagonalize a matrix the eigenvectors of which do not span the vector space of the appropriate dimension. load ("eigen")' loads this function. ueivects' is a synonym for uniteigenvectors'.  Function: unitvector (<x>)  Function: uvect (<x>)   Returns <x>/norm(<x>); this is a unit vector in the same direction as <x>. load ("eigen")' loads this function. uvect' is a synonym for unitvector'.  Function: vectorpotential (<givencurl>)   Returns the vector potential of a given curl vector, in the current coordinate system. potentialzeroloc' has a similar role as for potential', but the order of the left-hand sides of the equations must be a cyclic permutation of the coordinate variables.  Function: vectorsimp (<expr>)   Applies simplifications and expansions according to the following global flags: expandall', expanddot', expanddotplus', expandcross', expandcrossplus', expandcrosscross', expandgrad', expandgradplus', expandgradprod', expanddiv', expanddivplus', expanddivprod', expandcurl', expandcurlplus', expandcurlcurl', expandlaplacian', expandlaplacianplus', and expandlaplacianprod'. All these flags have default value false'. The plus' suffix refers to employing additivity or distributivity. The prod' suffix refers to the expansion for an operand that is any kind of product. expandcrosscross' Simplifies p ~ (q ~ r) to (p . r)*q - (p . q)*r. expandcurlcurl' Simplifies curl curl p to grad div p + div grad p. expandlaplaciantodivgrad' Simplifies laplacian p to div grad p. expandcross' Enables expandcrossplus' and expandcrosscross'. expandplus' Enables expanddotplus', expandcrossplus', expandgradplus', expanddivplus', expandcurlplus', and expandlaplacianplus'. expandprod' Enables expandgradprod', expanddivprod', and expandlaplacianprod'. These flags have all been declared evflag'.  Option variable: vect_cross   Default value: false' When vect_cross' is true', it allows DIFF(X~Y,T) to work where ~ is defined in SHARE;VECT (where VECT_CROSS is set to true', anyway.)  Function: zeromatrix (<m>, <n>)   Returns an <m> by <n> matrix, all elements of which are zero.  ## 24 Affine  Introduction to Affine Functions and Variables for Affine  ## 24.1 Introduction to Affine affine' is a package to work with groups of polynomials.  ## 24.2 Functions and Variables for Affine Function: fast_linsolve ([<expr_1>, ..., <expr_m>], [<x_1>, ..., <x_n>])   Solves the simultaneous linear equations <expr_1>, ..., <expr_m> for the variables <x_1>, ..., <x_n>. Each <expr_i> may be an equation or a general expression; if given as a general expression, it is treated as an equation of the form <expr_i> = 0'. The return value is a list of equations of the form [<x_1> = <a_1>, ..., <x_n> = <a_n>]' where <a_1>, ..., <a_n> are all free of <x_1>, ..., <x_n>. fast_linsolve' is faster than linsolve' for system of equations which are sparse. load(affine)' loads this function.  Function: grobner_basis ([<expr_1>, ..., <expr_m>])   Returns a Groebner basis for the equations <expr_1>, ..., <expr_m>. The function polysimp' can then be used to simplify other functions relative to the equations. grobner_basis ([3*x^2+1, y*x])$

polysimp (y^2*x + x^3*9 + 2) ==> -3*x + 2

polysimp(f)' yields 0 if and only if <f> is in the ideal
generated by <expr_1>, ..., <expr_m>, that is, if and only if <f>
is a polynomial combination of the elements of <expr_1>, ...,
<expr_m>.

load(affine)' loads this function.


Function: set_up_dot_simplifications

          set_up_dot_simplifications (<eqns>, <check_through_degree>)
set_up_dot_simplifications (<eqns>)
The <eqns> are polynomial equations in non commutative variables.
The value of current_variables' is the list of variables used for
computing degrees.  The equations must be homogeneous, in order
for the procedure to terminate.

If you have checked overlapping simplifications in
dot_simplifications' above the degree of <f>, then the following
is true: dotsimp (<f>)' yields 0 if and only if <f> is in the
ideal generated by the equations, i.e., if and only if <f> is a
polynomial combination of the elements of the equations.

The degree is that returned by nc_degree'.   This in turn is
influenced by the weights of individual variables.


Function: declare_weights (<x_1>, <w_1>, ..., <x_n>, <w_n>)

     Assigns weights <w_1>, ..., <w_n> to <x_1>, ..., <x_n>,
respectively.  These are the weights used in computing nc_degree'.


Function: nc_degree (<p>)

     Returns the degree of a noncommutative polynomial <p>.  See
declare_weights'.


Function: dotsimp (<f>)

     Returns 0 if and only if <f> is in the ideal generated by the
equations, i.e., if and only if <f> is a polynomial combination of
the elements of the equations.

load(affine)' loads this function.


Function: fast_central_elements ([<x_1>, ..., <x_n>], <n>)

     If set_up_dot_simplifications' has been previously done, finds
the central polynomials in the variables <x_1>, ..., <x_n> in the
given degree, <n>.

For example:
set_up_dot_simplifications ([y.x + x.y], 3);
fast_central_elements ([x, y], 2);
[y.y, x.x];

load(affine)' loads this function.


Function: check_overlaps (<n>, <add_to_simps>)

     Checks the overlaps thru degree <n>, making sure that you have
sufficient simplification rules in each degree, for dotsimp' to
work correctly.  This process can be speeded up if you know before
hand what the dimension of the space of monomials is.  If it is of
finite global dimension, then hilbert' should be used.  If you
don't know the monomial dimensions, do not specify a
rank_function'.  An optional third argument reset', false' says
don't bother to query about resetting things.

load(affine)' loads this function.


Function: mono ([<x_1>, ..., <x_n>], <n>)

     Returns the list of independent monomials relative to the current
dot simplifications of degree <n> in the variables <x_1>, ...,
<x_n>.


Function: monomial_dimensions (<n>)

     Compute the Hilbert series through degree <n> for the current
algebra.

load(affine)' loads this function.


Function: extract_linear_equations ([<p_1>, ..., <p_n>], [<m_1>, ..., <m_n>])

     Makes a list of the coefficients of the noncommutative polynomials
<p_1>, ..., <p_n> of the noncommutative monomials <m_1>, ...,
<m_n>.  The coefficients should be scalars.   Use
list_nc_monomials' to build the list of monomials.

load(affine)' loads this function.


Function: list_nc_monomials

          list_nc_monomials ([<p_1>, ..., <p_n>])
list_nc_monomials (<p>)
Returns a list of the non commutative monomials occurring in a
polynomial <p> or a list of polynomials <p_1>, ..., <p_n>.


Option variable: all_dotsimp_denoms

     Default value: false'

When all_dotsimp_denoms' is a list, the denominators encountered
by dotsimp' are appended to the list.  all_dotsimp_denoms' may
be initialized to an empty list []' before calling dotsimp'.

By default, denominators are not collected by dotsimp'.



## 25 itensor


Introduction to itensor
Functions and Variables for itensor


## 25.1 Introduction to itensor

Maxima implements symbolic tensor manipulation of two distinct types:
component tensor manipulation (ctensor' package) and indicial tensor
manipulation (itensor' package).

Nota bene: Please see the note on 'new tensor notation' below.

Component tensor manipulation means that geometrical tensor objects
are represented as arrays or matrices. Tensor operations such as
contraction or covariant differentiation are carried out by actually
summing over repeated (dummy) indices with do' statements.  That is,
one explicitly performs operations on the appropriate tensor components
stored in an array or matrix.

Indicial tensor manipulation is implemented by representing tensors
as functions of their covariant, contravariant and derivative indices.
Tensor operations such as contraction or covariant differentiation are
performed by manipulating the indices themselves rather than the
components to which they correspond.

These two approaches to the treatment of differential, algebraic and
analytic processes in the context of Riemannian geometry have various
particular nature and difficulty of the user's problem.  However, one
should keep in mind the following characteristics of the two
implementations:

The representation of tensors and tensor operations explicitly in
terms of their components makes ctensor' easy to use. Specification of
the metric and the computation of the induced tensors and invariants is
straightforward. Although all of Maxima's powerful simplification
capacity is at hand, a complex metric with intricate functional and
coordinate dependencies can easily lead to expressions whose size is
excessive and whose structure is hidden. In addition, many calculations
involve intermediate expressions which swell causing programs to
terminate before completion. Through experience, a user can avoid many
of these difficulties.

Because of the special way in which tensors and tensor operations
are represented in terms of symbolic operations on their indices,
expressions which in the component representation would be unmanageable
can sometimes be greatly simplified by using the special routines for
symmetrical objects in itensor'. In this way the structure of a large
expression may be more transparent. On the other hand, because of the
the special indicial representation in itensor', in some cases the
user may find difficulty with the specification of the metric, function
definition, and the evaluation of differentiated "indexed" objects.

The itensor' package can carry out differentiation with respect to
an indexed variable, which allows one to use the package when dealing
with Lagrangian and Hamiltonian formalisms. As it is possible to
differentiate a field Lagrangian with respect to an (indexed) field
variable, one can use Maxima to derive the corresponding Euler-Lagrange
equations in indicial form. These equations can be translated into
component tensor (ctensor') programs using the ic_convert' function,
allowing us to solve the field equations in a particular coordinate
representation, or to recast the equations of motion in Hamiltonian
form. See einhil.dem' and bradic.dem' for two comprehensive examples.
The first, einhil.dem', uses the Einstein-Hilbert action to derive the
Einstein field tensor in the homogeneous and isotropic case (Friedmann
equations) and the spherically symmetric, static case (Schwarzschild
solution.) The second, bradic.dem', demonstrates how to compute the
Friedmann equations from the action of Brans-Dicke gravity theory, and
also derives the Hamiltonian associated with the theory's scalar field.


## 25.2 Functions and Variables for itensor

Function: dispcon

          dispcon (<tensor_1>, <tensor_2>, ...)
dispcon (all)
Displays the contraction properties of its arguments as were given
to defcon'.  dispcon (all)' displays all the contraction
properties which were defined.


Function: entertensor (<name>)

     is a function which, by prompting, allows one to create an indexed
object called <name> with any number of tensorial and derivative
indices. Either a single index or a list of indices (which may be
null) is acceptable input (see the example under covdiff').


Function: changename (<old>, <new>, <expr>)

     will change the name of all indexed objects called <old> to <new>
in <expr>. <old> may be either a symbol or a list of the form
[<name>, <m>, <n>]' in which case only those indexed objects
called <name> with <m> covariant and <n> contravariant indices
will be renamed to <new>.


Function: listoftens

     Lists all tensors in a tensorial expression, complete with their
indices. E.g.,


Function: ishow (<expr>)

     displays <expr> with the indexed objects in it shown having their
covariant indices as subscripts and contravariant indices as
superscripts. The derivative indices are displayed as subscripts,
separated from the covariant indices by a comma (see the examples
throughout this document).


Function: indices (<expr>)

     Returns a list of two elements.  The first is a list of the free
indices in <expr> (those that occur only once). The second is the
list of the dummy indices in <expr> (those that occur exactly
twice) as the following example demonstrates.


Function: rename

          rename (<expr>)
rename (<expr>, <count>)
Returns an expression equivalent to <expr> but with the dummy
indices in each term chosen from the set [%1, %2,...]', if the
optional second argument is omitted. Otherwise, the dummy indices
are indexed beginning at the value of <count>.  Each dummy index
in a product will be different. For a sum, rename' will operate
upon each term in the sum resetting the counter with each term. In
this way rename' can serve as a tensorial simplifier. In
addition, the indices will be sorted alphanumerically (if allsym'
is true') with respect to covariant or contravariant indices
depending upon the value of flipflag'.  If flipflag' is false'
then the indices will be renamed according to the order of the
contravariant indices. If flipflag' is true' the renaming will
occur according to the order of the covariant indices. It often
happens that the combined effect of the two renamings will reduce
an expression more than either one by itself.


Function: show (<expr>)

     Displays expr' with the indexed objects in it shown having
covariant indices as subscripts, contravariant indices as
superscripts.  The derivative indices are displayed as subscripts,
separated from the covariant indices by a comma.


Option variable: flipflag

     Default value: false'

If false' then the indices will be renamed according to the order
of the contravariant indices, otherwise according to the order of
the covariant indices.

If flipflag' is false' then rename' forms a list of the
contravariant indices as they are encountered from left to right
(if true' then of the covariant indices). The first dummy index
in the list is renamed to %1', the next to %2', etc.  Then
sorting occurs after the rename'-ing (see the example under
rename').


Function: defcon

          defcon (<tensor_1>)
defcon (<tensor_1>, <tensor_2>, <tensor_3>)
gives <tensor_1> the property that the contraction of a product of
<tensor_1> and <tensor_2> results in <tensor_3> with the
appropriate indices.  If only one argument, <tensor_1>, is given,
then the contraction of the product of <tensor_1> with any indexed
object having the appropriate indices (say my_tensor') will yield
an indexed object with that name, i.e. my_tensor', and with a new
set of indices reflecting the contractions performed.      For
example, if imetric:g', then defcon(g)' will implement the
raising and lowering of indices through contraction with the metric
tensor.      More than one defcon' can be given for the same
indexed object; the latest one given which applies in a particular
contraction will be used.  contractions' is a list of those
indexed objects which have been given contraction properties with
defcon'.


Function: remcon

          remcon (<tensor_1>, ..., <tensor_n>)
remcon (all)
Removes all the contraction properties from the (<tensor_1>, ...,
<tensor_n>). remcon(all)' removes all contraction properties from
all indexed objects.


Function: contract (<expr>)

     Carries out the tensorial contractions in <expr> which may be any
combination of sums and products. This function uses the
information given to the defcon' function. For best results,
expr' should be fully expanded. ratexpand' is the fastest way to
expand products and powers of sums if there are no variables in
the denominators of the terms. The gcd' switch should be false'
if GCD cancellations are unnecessary.


Function: indexed_tensor (<tensor>)

     Must be executed before assigning components to a <tensor> for
which a built in value already exists as with ichr1', ichr2',
icurvature'. See the example under icurvature'.


Function: components (<tensor>, <expr>)

     permits one to assign an indicial value to an expression <expr>
giving the values of the components of <tensor>. These are
automatically substituted for the tensor whenever it occurs with
all of its indices. The tensor must be of the form t([...],[...])'
where either list may be empty. <expr> can be any indexed
expression involving other objects with the same free indices as
<tensor>. When used to assign values to the metric tensor wherein
the components contain dummy indices one must be careful to define
these indices to avoid the generation of multiple dummy indices.
Removal of this assignment is given to the function remcomps'.

It is important to keep in mind that components' cares only about
the valence of a tensor, not about any particular index ordering.
Thus assigning components to, say, x([i,-j],[])', x([-j,i],[])',
or x([i],[j])' all produce the same result, namely components
being assigned to a tensor named x' with valence (1,1)'.

Components can be assigned to an indexed expression in four ways,
two of which involve the use of the components' command:

1) As an indexed expression. For instance:

(%i2) components(g([],[i,j]),e([],[i])*p([],[j]))$(%i3) ishow(g([],[i,j]))$
i  j
(%t3)                                e  p

2) As a matrix:


Function: remcomps (<tensor>)

     Unbinds all values from <tensor> which were assigned with the
components' function.


Function: showcomps (<tensor>)

     Shows component assignments of a tensor, as made using the
components' command. This function can be particularly useful
when a matrix is assigned to an indicial tensor using
components', as demonstrated by the following example:


Function: idummy ()

     Increments icounter' and returns as its value an index of the form
%n' where n is a positive integer.  This guarantees that dummy
indices which are needed in forming expressions will not conflict
with indices already in use (see the example under indices').


Option variable: idummyx

     Default value: %'

Is the prefix for dummy indices (see the example under indices').


Option variable: icounter

     Default value: 1'

Determines the numerical suffix to be used in generating the next
dummy index in the tensor package.  The prefix is determined by
the option idummy' (default: %').


Function: kdelta (<L1>, <L2>)

     is the generalized Kronecker delta function defined in the
itensor' package with <L1> the list of covariant indices and <L2>
the list of contravariant indices.  kdelta([i],[j])' returns the
ordinary Kronecker delta.  The command ev(<expr>,kdelta)' causes
the evaluation of an expression containing kdelta([],[])' to the
dimension of the manifold.

In what amounts to an abuse of this notation, itensor' also allows
kdelta' to have 2 covariant and no contravariant, or 2
contravariant and no covariant indices, in effect providing a
co(ntra)variant "unit matrix" capability. This is strictly
considered a programming aid and not meant to imply that
kdelta([i,j],[])' is a valid tensorial object.


Function: kdels (<L1>, <L2>)

     Symmetrized Kronecker delta, used in some calculations. For
instance:


Function: levi_civita (<L>)

     is the permutation (or Levi-Civita) tensor which yields 1 if the
list <L> consists of an even permutation of integers, -1 if it
consists of an odd permutation, and 0 if some indices in <L> are
repeated.


Function: lc2kdt (<expr>)

     Simplifies expressions containing the Levi-Civita symbol,
converting these to Kronecker-delta expressions when possible. The
main difference between this function and simply evaluating the
Levi-Civita symbol is that direct evaluation often results in
Kronecker expressions containing numerical indices. This is often
undesirable as it prevents further simplification.  The lc2kdt'
function avoids this problem, yielding expressions that are more
easily simplified with rename' or contract'.


Function: lc_l

     Simplification rule used for expressions containing the
unevaluated Levi-Civita symbol (levi_civita'). Along with lc_u',
it can be used to simplify many expressions more efficiently than
the evaluation of levi_civita'.  For example:


Function: lc_u

     Simplification rule used for expressions containing the
unevaluated Levi-Civita symbol (levi_civita'). Along with lc_u',
it can be used to simplify many expressions more efficiently than
the evaluation of levi_civita'.  For details, see lc_l'.


Function: canten (<expr>)

     Simplifies <expr> by renaming (see rename') and permuting dummy
indices. rename' is restricted to sums of tensor products in
which no derivatives are present. As such it is limited and should
only be used if canform' is not capable of carrying out the
required simplification.

The canten' function returns a mathematically correct result only
if its argument is an expression that is fully symmetric in its
indices.  For this reason, canten' returns an error if allsym'
is not set to true'.


Function: concan (<expr>)

     Similar to canten' but also performs index contraction.


Option variable: allsym

     Default value: false'

If true' then all indexed objects are assumed symmetric in all of
their covariant and contravariant indices. If false' then no
symmetries of any kind are assumed in these indices. Derivative
indices are always taken to be symmetric unless iframe_flag' is
set to true'.


Function: decsym (<tensor>, <m>, <n>, [<cov_1>, <cov_2>, ...], [<contr_1>, <contr_2>, ...])

     Declares symmetry properties for <tensor> of <m> covariant and <n>
contravariant indices. The <cov_i> and <contr_i> are
pseudofunctions expressing symmetry relations among the covariant
and contravariant indices respectively.  These are of the form
symoper(<index_1>, <index_2>,...)' where symoper' is one of
sym', anti' or cyc' and the <index_i> are integers indicating
the position of the index in the <tensor>.  This will declare
<tensor> to be symmetric, antisymmetric or cyclic respectively in
the <index_i>. symoper(all)' is also an allowable form which
indicates all indices obey the symmetry condition. For example,
given an object b' with 5 covariant indices,
decsym(b,5,3,[sym(1,2),anti(3,4)],[cyc(all)])' declares b'
symmetric in its first and second and antisymmetric in its third
and fourth covariant indices, and cyclic in all of its
contravariant indices.  Either list of symmetry declarations may
be null.  The function which performs the simplifications is
canform' as the example below illustrates.


Function: remsym (<tensor>, <m>, <n>)

     Removes all symmetry properties from <tensor> which has <m>
covariant indices and <n> contravariant indices.


Function: canform

          canform (<expr>)
canform (<expr>, <rename>)
Simplifies <expr> by renaming dummy indices and reordering all
indices as dictated by symmetry conditions imposed on them. If
allsym' is true' then all indices are assumed symmetric,
otherwise symmetry information provided by decsym' declarations
will be used. The dummy indices are renamed in the same manner as
in the rename' function. When canform' is applied to a large
expression the calculation may take a considerable amount of time.
This time can be shortened by calling rename' on the expression
first.  Also see the example under decsym'. Note: canform' may
not be able to reduce an expression completely to its simplest
form although it will always return a mathematically correct
result.

The optional second parameter <rename>, if set to false',
suppresses renaming.


Function: diff (<expr>, <v_1>, [<n_1>, [<v_2>, <n_2>] ...])

     is the usual Maxima differentiation function which has been
expanded in its abilities for itensor'. It takes the derivative
of <expr> with respect to <v_1> <n_1> times, with respect to <v_2>
<n_2> times, etc. For the tensor package, the function has been
modified so that the <v_i> may be integers from 1 up to the value
of the variable dim'.  This will cause the differentiation to be
carried out with respect to the <v_i>th member of the list
vect_coords'.  If vect_coords' is bound to an atomic variable,
then that variable subscripted by <v_i> will be used for the
variable of differentiation.  This permits an array of coordinate
names or subscripted names like x', x', ...  to be used.

A further extension adds the ability to diff' to compute
derivatives with respect to an indexed variable. In particular,
the tensor package knows how to differentiate expressions
containing combinations of the metric tensor and its derivatives
with respect to the metric tensor and its first and second
derivatives. This capability is particularly useful when
considering Lagrangian formulations of a gravitational theory,
allowing one to derive the Einstein tensor and field equations
from the action principle.


Function: idiff (<expr>, <v_1>, [<n_1>, [<v_2>, <n_2>] ...])

     Indicial differentiation. Unlike diff', which differentiates with
respect to an independent variable, idiff)' can be used to
differentiate with respect to a coordinate. For an indexed object,
this amounts to appending the <v_i> as derivative indices.
Subsequently, derivative indices will be sorted, unless
iframe_flag' is set to true'.

idiff' can also differentiate the determinant of the metric
tensor. Thus, if imetric' has been bound to G' then
idiff(determinant(g),k)' will return 2 * determinant(g) *
ichr2([%i,k],[%i])' where the dummy index %i' is chosen
appropriately.


Function: liediff (<v>, <ten>)

     Computes the Lie-derivative of the tensorial expression <ten> with
respect to the vector field <v>. <ten> should be any indexed
tensor expression; <v> should be the name (without indices) of a
vector field. For example:


Function: rediff (<ten>)

     Evaluates all occurrences of the idiff' command in the tensorial
expression <ten>.


Function: undiff (<expr>)

     Returns an expression equivalent to <expr> but with all derivatives
of indexed objects replaced by the noun form of the idiff'
function. Its arguments would yield that indexed object if the
differentiation were carried out.  This is useful when it is
desired to replace a differentiated indexed object with some
function definition resulting in <expr> and then carry out the
differentiation by saying ev(<expr>, idiff)'.


Function: evundiff (<expr>)

     Equivalent to the execution of undiff', followed by ev' and
rediff'.

The point of this operation is to easily evalute expressions that
cannot be directly evaluated in derivative form. For instance, the
following causes an error:

(%o1)      /share/tensor/itensor.lisp
(%i2) icurvature([i,j,k],[l],m);
Maxima encountered a Lisp error:

Error in $ICURVATURE [or a callee]:$ICURVATURE [or a callee] requires less than three arguments.

Automatically continuing.
To reenable the Lisp debugger set *debugger-hook* to nil.

However, if icurvature' is entered in noun form, it can be
evaluated using evundiff':

(%i3) ishow('icurvature([i,j,k],[l],m))$l (%t3) icurvature i j k,m (%i4) ishow(evundiff(%))$
l              l         %1           l           %1
(%t4) - ichr2        - ichr2     ichr2      - ichr2       ichr2
i k,j m        %1 j      i k,m        %1 j,m      i k

l              l         %1           l           %1
+ ichr2        + ichr2     ichr2      + ichr2       ichr2
i j,k m        %1 k      i j,m        %1 k,m      i j

Note: In earlier versions of Maxima, derivative forms of the
Christoffel-symbols also could not be evaluated. This has been
fixed now, so evundiff' is no longer necessary for expressions
like this:

(%i5) imetric(g);
(%o5)                                done
(%i6) ishow(ichr2([i,j],[k],l))$k %3 g (g - g + g ) j %3,i l i j,%3 l i %3,j l (%t6) ----------------------------------------- 2 k %3 g (g - g + g ) ,l j %3,i i j,%3 i %3,j + ----------------------------------- 2  Function: flush (<expr>, <tensor_1>, <tensor_2>, ...)   Set to zero, in <expr>, all occurrences of the <tensor_i> that have no derivative indices.  Function: flushd (<expr>, <tensor_1>, <tensor_2>, ...)   Set to zero, in <expr>, all occurrences of the <tensor_i> that have derivative indices.  Function: flushnd (<expr>, <tensor>, <n>)   Set to zero, in <expr>, all occurrences of the differentiated object <tensor> that have <n> or more derivative indices as the following example demonstrates. (%i1) load(itensor); (%o1) /share/tensor/itensor.lisp (%i2) ishow(a([i],[J,r],k,r)+a([i],[j,r,s],k,r,s))$
J r      j r s
(%t2)                          a      + a
i,k r    i,k r s
(%i3) ishow(flushnd(%,a,3))$J r (%t3) a i,k r  Function: coord (<tensor_1>, <tensor_2>, ...)   Gives <tensor_i> the coordinate differentiation property that the derivative of contravariant vector whose name is one of the <tensor_i> yields a Kronecker delta. For example, if coord(x)' has been done then idiff(x([],[i]),j)' gives kdelta([i],[j])'. coord' is a list of all indexed objects having this property.  Function: remcoord   remcoord (<tensor_1>, <tensor_2>, ...) remcoord (all) Removes the coordinate differentiation property from the tensor_i' that was established by the function coord'. remcoord(all)' removes this property from all indexed objects.  Function: makebox (<expr>)   Display <expr> in the same manner as show'; however, any tensor d'Alembertian occurring in <expr> will be indicated using the symbol []'. For example, []p([m],[n])' represents g([],[i,j])*p([m],[n],i,j)'.  Function: conmetderiv (<expr>, <tensor>)   Simplifies expressions containing ordinary derivatives of both covariant and contravariant forms of the metric tensor (the current restriction). For example, conmetderiv' can relate the derivative of the contravariant metric tensor with the Christoffel symbols as seen from the following:  Function: simpmetderiv   simpmetderiv (<expr>) simpmetderiv (<expr>[, <stop>]) Simplifies expressions containing products of the derivatives of the metric tensor. Specifically, simpmetderiv' recognizes two identities:  Function: flush1deriv (<expr>, <tensor>)   Set to zero, in expr', all occurrences of tensor' that have exactly one derivative index.  Function: imetric (<g>)  System variable: imetric   Specifies the metric by assigning the variable imetric:<g>' in addition, the contraction properties of the metric <g> are set up by executing the commands defcon(<g>), defcon(<g>, <g>, kdelta)'. The variable imetric' (unbound by default), is bound to the metric, assigned by the imetric(<g>)' command.  Function: idim (<n>)   Sets the dimensions of the metric. Also initializes the antisymmetry properties of the Levi-Civita symbols for the given dimension.  Function: ichr1 ([<i>, <j>, <k>])   Yields the Christoffel symbol of the first kind via the definition (g + g - g )/2 . ik,j jk,i ij,k To evaluate the Christoffel symbols for a particular metric, the variable imetric' must be assigned a name as in the example under chr2'.  Function: ichr2 ([<i>, <j>], [<k>])   Yields the Christoffel symbol of the second kind defined by the relation ks ichr2([i,j],[k]) = g (g + g - g )/2 is,j js,i ij,s  Function: icurvature ([<i>, <j>, <k>], [<h>])   Yields the Riemann curvature tensor in terms of the Christoffel symbols of the second kind (ichr2'). The following notation is used: h h h %1 h icurvature = - ichr2 - ichr2 ichr2 + ichr2 i j k i k,j %1 j i k i j,k h %1 + ichr2 ichr2 %1 k i j  Function: covdiff (<expr>, <v_1>, <v_2>, ...)   Yields the covariant derivative of <expr> with respect to the variables <v_i> in terms of the Christoffel symbols of the second kind (ichr2'). In order to evaluate these, one should use ev(<expr>,ichr2)'.  Function: lorentz_gauge (<expr>)   Imposes the Lorentz condition by substituting 0 for all indexed objects in <expr> that have a derivative index identical to a contravariant index.  Function: igeodesic_coords (<expr>, <name>)   Causes undifferentiated Christoffel symbols and first derivatives of the metric tensor vanish in <expr>. The <name> in the igeodesic_coords' function refers to the metric <name> (if it appears in <expr>) while the connection coefficients must be called with the names ichr1' and/or ichr2'. The following example demonstrates the verification of the cyclic identity satisfied by the Riemann curvature tensor using the igeodesic_coords' function.  Function: iframes ()   Since in this version of Maxima, contraction identities for ifr' and ifri' are always defined, as is the frame bracket (ifb'), this function does nothing.  Variable: ifb   The frame bracket. The contribution of the frame metric to the connection coefficients is expressed using the frame bracket:  Variable: icc1   Connection coefficients of the first kind. In itensor', defined as  Variable: icc2   Connection coefficients of the second kind. In itensor', defined as  Variable: ifc1   Frame coefficient of the first kind (also known as Ricci-rotation coefficients.) This tensor represents the contribution of the frame metric to the connection coefficient of the first kind. Defined as:  Variable: ifc2   Frame coefficient of the second kind. This tensor represents the contribution of the frame metric to the connection coefficient of the second kind. Defined as a permutation of the frame bracket (ifb') with the appropriate indices raised and lowered as necessary:  Variable: ifr   The frame field. Contracts with the inverse frame field (ifri') to form the frame metric (ifg').  Variable: ifri   The inverse frame field. Specifies the frame base (dual basis vectors). Along with the frame metric, it forms the basis of all calculations based on frames.  Variable: ifg   The frame metric. Defaults to kdelta', but can be changed using components'.  Variable: ifgi   The inverse frame metric. Contracts with the frame metric (ifg') to kdelta'.  Option variable: iframe_bracket_form   Default value: true' Specifies how the frame bracket (ifb') is computed.  Variable: inm   The nonmetricity vector. Conformal nonmetricity is defined through the covariant derivative of the metric tensor. Normally zero, the metric tensor's covariant derivative will evaluate to the following when inonmet_flag' is set to true':  Variable: inmc1   Covariant permutation of the nonmetricity vector components. Defined as  Variable: inmc2   Contravariant permutation of the nonmetricity vector components. Used in the connection coefficients if inonmet_flag' is true'. Defined as:  Variable: ikt1   Covariant permutation of the torsion tensor (also known as contorsion). Defined as:  Variable: ikt2   Contravariant permutation of the torsion tensor (also known as contorsion). Defined as:  Variable: itr   The torsion tensor. For a metric with torsion, repeated covariant differentiation on a scalar function will not commute, as demonstrated by the following example:  Operator: ~   The wedge product operator is denoted by the tilde ~'. This is a binary operator. Its arguments should be expressions involving scalars, covariant tensors of rank one, or covariant tensors of rank l' that have been declared antisymmetric in all covariant indices. The behavior of the wedge product operator is controlled by the igeowedge_flag' flag, as in the following example: (%i1) load(itensor); (%o1) /share/tensor/itensor.lisp (%i2) ishow(a([i])~b([j]))$
a  b  - b  a
i  j    i  j
(%t2)                            -------------
2
(%i3) decsym(a,2,0,[anti(all)],[]);
(%o3)                                done
(%i4) ishow(a([i,j])~b([k]))$a b + b a - a b i j k i j k i k j (%t4) --------------------------- 3 (%i5) igeowedge_flag:true; (%o5) true (%i6) ishow(a([i])~b([j]))$
(%t6)                            a  b  - b  a
i  j    i  j
(%i7) ishow(a([i,j])~b([k]))$(%t7) a b + b a - a b i j k i j k i k j  Operator: |   The vertical bar |' denotes the "contraction with a vector" binary operation. When a totally antisymmetric covariant tensor is contracted with a contravariant vector, the result is the same regardless which index was used for the contraction. Thus, it is possible to define the contraction operation in an index-free manner. In the itensor' package, contraction with a vector is always carried out with respect to the first index in the literal sorting order. This ensures better simplification of expressions involving the |' operator. For instance: (%i1) load(itensor); (%o1) /share/tensor/itensor.lisp (%i2) decsym(a,2,0,[anti(all)],[]); (%o2) done (%i3) ishow(a([i,j],[])|v)$
%1
(%t3)                              v   a
%1 j
(%i4) ishow(a([j,i],[])|v)$%1 (%t4) - v a %1 j Note that it is essential that the tensors used with the |' operator be declared totally antisymmetric in their covariant indices. Otherwise, the results will be incorrect.  Function: extdiff (<expr>, <i>)   Computes the exterior derivative of <expr> with respect to the index <i>. The exterior derivative is formally defined as the wedge product of the partial derivative operator and a differential form. As such, this operation is also controlled by the setting of igeowedge_flag'. For instance: (%i1) load(itensor); (%o1) /share/tensor/itensor.lisp (%i2) ishow(extdiff(v([i]),j))$
v    - v
j,i    i,j
(%t2)                             -----------
2
(%i3) decsym(a,2,0,[anti(all)],[]);
(%o3)                                done
(%i4) ishow(extdiff(a([i,j]),k))$a - a + a j k,i i k,j i j,k (%t4) ------------------------ 3 (%i5) igeowedge_flag:true; (%o5) true (%i6) ishow(extdiff(v([i]),j))$
(%t6)                             v    - v
j,i    i,j
(%i7) ishow(extdiff(a([i,j]),k))$(%t7) - (a - a + a ) k j,i k i,j j i,k  Function: hodge (<expr>)   Compute the Hodge-dual of <expr>. For instance:  Option variable: igeowedge_flag   Default value: false' Controls the behavior of the wedge product and exterior derivative. When set to false' (the default), the notion of differential forms will correspond with that of a totally antisymmetric covariant tensor field. When set to true', differential forms will agree with the notion of the volume element.  Function: tentex (<expr>)   To use the tentex' function, you must first load tentex', as in the following example: (%i1) load(itensor); (%o1) /share/tensor/itensor.lisp (%i2) load(tentex); (%o2) /share/tensor/tentex.lisp (%i3) idummyx:m; (%o3) m (%i4) ishow(icurvature([j,k,l],[i]))$
m1       i           m1       i           i
(%t4)  ichr2    ichr2     - ichr2    ichr2     - ichr2
j k      m1 l        j l      m1 k        j l,k

i
+ ichr2
j k,l
(%i5) tentex(%)$$$\Gamma_{j\,k}^{m_1}\,\Gamma_{l\,m_1}^{i}-\Gamma_{j\,l}^{m_1}\, \Gamma_{k\,m_1}^{i}-\Gamma_{j\,l,k}^{i}+\Gamma_{j\,k,l}^{i}$$ Note the use of the idummyx' assignment, to avoid the appearance of the percent sign in the TeX expression, which may lead to compile errors. NB: This version of the tentex' function is somewhat experimental.  Function: ic_convert (<eqn>)   Converts the itensor' equation <eqn> to a ctensor' assignment statement. Implied sums over dummy indices are made explicit while indexed objects are transformed into arrays (the array subscripts are in the order of covariant followed by contravariant indices of the indexed objects). The derivative of an indexed object will be replaced by the noun form of diff' taken with respect to ct_coords' subscripted by the derivative index. The Christoffel symbols ichr1' and ichr2' will be translated to lcs' and mcs', respectively and if metricconvert' is true' then all occurrences of the metric with two covariant (contravariant) indices will be renamed to lg' (ug'). In addition, do' loops will be introduced summing over all free indices so that the transformed assignment statement can be evaluated by just doing ev'. The following examples demonstrate the features of this function. (%i1) load(itensor); (%o1) /share/tensor/itensor.lisp (%i2) eqn:ishow(t([i,j],[k])=f([],[])*g([l,m],[])*a([],[m],j) *b([i],[l,k]))$
k        m   l k
(%t2)                       t    = f a   b    g
i j      ,j  i    l m
(%i3) ic_convert(eqn);
(%o3) for i thru dim do (for j thru dim do (
for k thru dim do
t        : f sum(sum(diff(a , ct_coords ) b
i, j, k                   m           j   i, l, k

g    , l, 1, dim), m, 1, dim)))
l, m
(%i4) imetric(g);
(%o4)                                done
(%i5) metricconvert:true;
(%o5)                                true
(%i6) ic_convert(eqn);
(%o6) for i thru dim do (for j thru dim do (
for k thru dim do
t        : f sum(sum(diff(a , ct_coords ) b
i, j, k                   m           j   i, l, k

lg    , l, 1, dim), m, 1, dim)))
l, m



## 26 ctensor


Introduction to ctensor
Functions and Variables for ctensor


## 26.1 Introduction to ctensor

ctensor' is a component tensor manipulation package.  To use the
ctensor' package, type load(ctensor)'.  To begin an interactive
session with ctensor', type csetup()'.  You are first asked to
specify the dimension of the manifold. If the dimension is 2, 3 or 4
then the list of coordinates defaults to [x,y]', [x,y,z]' or
[x,y,z,t]' respectively.  These names may be changed by assigning a
new list of coordinates to the variable ct_coords' (described below)
coordinate names conflicting with other object definitions.

Next, the user enters the metric either directly or from a file by
specifying its ordinal position.  The metric is stored in the matrix
lg'. Finally, the metric inverse is computed and stored in the matrix
ug'. One has the option of carrying out all calculations in a power
series.

A sample protocol is begun below for the static, spherically
symmetric metric (standard coordinates) which will be applied to the
problem of deriving Einstein's vacuum equations (which lead to the
Schwarzschild solution) as an example. Many of the functions in
ctensor' will be displayed for the standard metric as examples.

(%o1)      /share/tensor/ctensor.mac
(%i2) csetup();
Enter the dimension of the coordinate system:
4;
Do you wish to change the coordinate names?
n;
Do you want to
1. Enter a new metric?

2. Enter a metric from a file?

3. Approximate a metric with a Taylor series?
1;

Is the matrix  1. Diagonal  2. Symmetric  3. Antisymmetric  4. General
Answer 1, 2, 3 or 4
1;
Row 1 Column 1:
a;
Row 2 Column 2:
x^2;
Row 3 Column 3:
x^2*sin(y)^2;
Row 4 Column 4:
-d;

Matrix entered.
Enter functional dependencies with the DEPENDS function or 'N' if none
depends([a,d],x);
Do you wish to see the metric?
y;
[ a  0       0        0  ]
[                        ]
[     2                  ]
[ 0  x       0        0  ]
[                        ]
[         2    2         ]
[ 0  0   x  sin (y)   0  ]
[                        ]
[ 0  0       0       - d ]
(%o2)                                done
(%i3) christof(mcs);
a
x
(%t3)                          mcs        = ---
1, 1, 1   2 a

1
(%t4)                           mcs        = -
1, 2, 2   x

1
(%t5)                           mcs        = -
1, 3, 3   x

d
x
(%t6)                          mcs        = ---
1, 4, 4   2 d

x
(%t7)                          mcs        = - -
2, 2, 1     a

cos(y)
(%t8)                         mcs        = ------
2, 3, 3   sin(y)

2
x sin (y)
(%t9)                      mcs        = - ---------
3, 3, 1         a

(%t10)                   mcs        = - cos(y) sin(y)
3, 3, 2

d
x
(%t11)                         mcs        = ---
4, 4, 1   2 a
(%o11)                               done


## 26.2 Functions and Variables for ctensor

Function: csetup ()

     A function in the ctensor' (component tensor) package which
initializes the package and allows the user to enter a metric
interactively. See ctensor' for more details.


Function: cmetric

          cmetric (<dis>)
cmetric ()
A function in the ctensor' (component tensor) package that
computes the metric inverse and sets up the package for further
calculations.

If cframe_flag' is false', the function computes the inverse
metric ug' from the (user-defined) matrix lg'. The metric
determinant is also computed and stored in the variable gdet'.
Furthermore, the package determines if the metric is diagonal and
sets the value of diagmetric' accordingly. If the optional
argument <dis> is present and not equal to false', the user is
prompted to see the metric inverse.

If cframe_flag' is true', the function expects that the values of
fri' (the inverse frame matrix) and lfg' (the frame metric) are
defined. From these, the frame matrix fr' and the inverse frame
metric ufg' are computed.


Function: ct_coordsys

          ct_coordsys (<coordinate_system>, <extra_arg>)
ct_coordsys (<coordinate_system>)
Sets up a predefined coordinate system and metric. The argument
<coordinate_system> can be one of the following symbols:


Function: init_ctensor ()

     Initializes the ctensor' package.

The init_ctensor' function reinitializes the ctensor' package.
It removes all arrays and matrices used by ctensor', resets all
flags, resets dim' to 4, and resets the frame metric to the
Lorentz-frame.


Function: christof (<dis>)

     A function in the ctensor' (component tensor) package.  It
computes the Christoffel symbols of both kinds.  The argument
<dis> determines which results are to be immediately displayed.
The Christoffel symbols of the first and second kinds are stored
in the arrays lcs[i,j,k]' and mcs[i,j,k]' respectively and
defined to be symmetric in the first two indices. If the argument
to christof' is lcs' or mcs' then the unique non-zero values of
lcs[i,j,k]' or mcs[i,j,k]', respectively, will be displayed. If
the argument is all' then the unique non-zero values of
lcs[i,j,k]' and mcs[i,j,k]' will be displayed.  If the argument
is false' then the display of the elements will not occur. The
array elements mcs[i,j,k]' are defined in such a manner that the
final index is contravariant.


Function: ricci (<dis>)

     A function in the ctensor' (component tensor) package. ricci'
computes the covariant (symmetric) components ric[i,j]' of the
Ricci tensor.  If the argument <dis> is true', then the non-zero
components are displayed.


Function: uricci (<dis>)

     This function first computes the covariant components ric[i,j]'
of the Ricci tensor.  Then the mixed Ricci tensor is computed
using the contravariant metric tensor.  If the value of the
argument <dis> is true', then these mixed components, uric[i,j]'
(the index i' is covariant and the index j' is contravariant),
will be displayed directly.  Otherwise, ricci(false)' will simply
compute the entries of the array uric[i,j]' without displaying
the results.


Function: scurvature ()

     Returns the scalar curvature (obtained by contracting the Ricci
tensor) of the Riemannian manifold with the given metric.


Function: einstein (<dis>)

     A function in the ctensor' (component tensor) package.
einstein' computes the mixed Einstein tensor after the
Christoffel symbols and Ricci tensor have been obtained (with the
functions christof' and ricci').  If the argument <dis> is
true', then the non-zero values of the mixed Einstein tensor
ein[i,j]' will be displayed where j' is the contravariant index.
The variable rateinstein' will cause the rational simplification
on these components. If ratfac' is true' then the components will
also be factored.


Function: leinstein (<dis>)

     Covariant Einstein-tensor. leinstein' stores the values of the
covariant Einstein tensor in the array lein'. The covariant
Einstein-tensor is computed from the mixed Einstein tensor ein'
by multiplying it with the metric tensor. If the argument <dis> is
true', then the non-zero values of the covariant Einstein tensor
are displayed.


Function: riemann (<dis>)

     A function in the ctensor' (component tensor) package.  riemann'
computes the Riemann curvature tensor from the given metric and
the corresponding Christoffel symbols. The following index
conventions are used:

l      _l       _l       _l   _m    _l   _m
R[i,j,k,l] =  R    = |      - |      + |    |   - |    |
ijk     ij,k     ik,j     mk   ij    mj   ik

This notation is consistent with the notation used by the itensor'
package and its icurvature' function.  If the optional argument
<dis> is true', the unique non-zero components riem[i,j,k,l]'
will be displayed.  As with the Einstein tensor, various switches
set by the user control the simplification of the components of
the Riemann tensor.  If ratriemann' is true', then rational
simplification will be done. If ratfac' is true' then each of
the components will also be factored.

If the variable cframe_flag' is false', the Riemann tensor is
computed directly from the Christoffel-symbols. If cframe_flag' is
true', the covariant Riemann-tensor is computed first from the
frame field coefficients.


Function: lriemann (<dis>)

     Covariant Riemann-tensor (lriem[]').

Computes the covariant Riemann-tensor as the array lriem'. If the
argument <dis> is true', unique non-zero values are displayed.

If the variable cframe_flag' is true', the covariant Riemann
tensor is computed directly from the frame field coefficients.
Otherwise, the (3,1) Riemann tensor is computed first.

For information on index ordering, see riemann'.


Function: uriemann (<dis>)

     Computes the contravariant components of the Riemann curvature
tensor as array elements uriem[i,j,k,l]'.  These are displayed if
<dis> is true'.


Function: rinvariant ()

     Forms the Kretchmann-invariant (kinvariant') obtained by
contracting the tensors

lriem[i,j,k,l]*uriem[i,j,k,l].

This object is not automatically simplified since it can be very
large.


Function: weyl (<dis>)

     Computes the Weyl conformal tensor.  If the argument <dis> is
true', the non-zero components weyl[i,j,k,l]' will be displayed
to the user.  Otherwise, these components will simply be computed
and stored.  If the switch ratweyl' is set to true', then the
components will be rationally simplified; if ratfac' is true'
then the results will be factored as well.


Function: ctaylor ()

     The ctaylor' function truncates its argument by converting it to
a Taylor-series using taylor', and then calling ratdisrep'. This
has the combined effect of dropping terms higher order in the
expansion variable ctayvar'. The order of terms that should be
dropped is defined by ctaypov'; the point around which the series
expansion is carried out is specified in ctaypt'.

As an example, consider a simple metric that is a perturbation of
the Minkowski metric. Without further restrictions, even a diagonal
metric produces expressions for the Einstein tensor that are far
too complex:


Function: frame_bracket (<fr>, <fri>, <diagframe>)

     The frame bracket (fb[]').

Computes the frame bracket according to the following definition:

c          c         c        d     e
ifb   = ( ifri    - ifri    ) ifr   ifr
ab         d,e       e,d      a     b


Function: nptetrad ()

     Computes a Newman-Penrose null tetrad (np') and its raised-index
counterpart (npi'). See petrov' for an example.

The null tetrad is constructed on the assumption that a
four-dimensional orthonormal frame metric with metric signature
(-,+,+,+) is being used.  The components of the null tetrad are
related to the inverse frame matrix as follows:


Function: psi (<dis>)

     Computes the five Newman-Penrose coefficients psi'...psi'.
If dis' is set to true', the coefficients are displayed.  See
petrov' for an example.

These coefficients are computed from the Weyl-tensor in a
coordinate base.  If a frame base is used, the Weyl-tensor is
first converted to a coordinate base, which can be a
computationally expensive procedure. For this reason, in some
cases it may be more advantageous to use a coordinate base in the
first place before the Weyl tensor is computed. Note however, that
constructing a Newman-Penrose null tetrad requires a frame base.
Therefore, a meaningful computation sequence may begin with a
frame base, which is then used to compute lg' (computed
automatically by cmetric') and then ug'. See petrov' for an
example. At this point, you can switch back to a coordinate base
by setting cframe_flag' to false before beginning to compute the
Christoffel symbols. Changing to a frame base at a later stage
could yield inconsistent results, as you may end up with a mixed
bag of tensors, some computed in a frame base, some in a
coordinate base, with no means to distinguish between the two.


Function: petrov ()

     Computes the Petrov classification of the metric characterized by
psi'...psi'.

For example, the following demonstrates how to obtain the
Petrov-classification of the Kerr metric:

(%o1)       /share/tensor/ctensor.mac
(%i2) (cframe_flag:true,gcd:spmod,ctrgsimp:true,ratfac:true);
(%o2)                                true
(%i3) ct_coordsys(exteriorschwarzschild,all);
(%o3)                                done
(%i4) ug:invert(lg)\$
(%i5) weyl(false);
(%o5)                                done
(%t6) np =

[ sqrt(r - 2 m)           sqrt(r)                                 ]
[---------------   ---------------------    0            0        ]
[sqrt(2) sqrt(r)   sqrt(2) sqrt(r - 2 m)                          ]
[                                                                 ]
[ sqrt(r - 2 m)            sqrt(r)                                ]
[---------------  - ---------------------   0            0        ]
[sqrt(2) sqrt(r)    sqrt(2) sqrt(r - 2 m)                         ]
[                                                                 ]
[                                          r      %i r sin(theta) ]
[       0                    0          -------   --------------- ]
[                                       sqrt(2)       sqrt(2)     ]
[                                                                 ]
[                                          r       %i r sin(theta)]
[       0                    0          -------  - ---------------]
[                                       sqrt(2)        sqrt(2)    ]

sqrt(r)         sqrt(r - 2 m)
(%t7) npi = matrix([- ---------------------,---------------, 0, 0],
sqrt(2) sqrt(r - 2 m) sqrt(2) sqrt(r)

sqrt(r)            sqrt(r - 2 m)
[- ---------------------, - ---------------, 0, 0],
sqrt(2) sqrt(r - 2 m)    sqrt(2) sqrt(r)

1               %i
[0, 0, ---------, --------------------],
sqrt(2) r  sqrt(2) r sin(theta)

1                 %i
[0, 0, ---------, - --------------------])
sqrt(2) r    sqrt(2) r sin(theta)

(%o7)                                done
(%i7) psi(true);
(%t8)                              psi  = 0
0

(%t9)                              psi  = 0
1

m
(%t10)                             psi  = --
2    3
r

(%t11)                             psi  = 0
3

(%t12)                             psi  = 0
4
(%o12)                               done
(%i12) petrov();
(%o12)                                 D

The Petrov classification function is based on the algorithm
published in "Classifying geometries in general relativity: III
Classification in practice" by Pollney, Skea, and d'Inverno,
Class. Quant. Grav. 17 2885-2902 (2000).  Except for some simple
test cases, the implementation is untested as of December 19,
2004, and is likely to contain errors.


Function: contortion (<tr>)

     Computes the (2,1) contortion coefficients from the torsion tensor
<tr>.


Function: nonmetricity (<nm>)

     Computes the (2,1) nonmetricity coefficients from the nonmetricity
vector <nm>.


Function: ctransform (<M>)

     A function in the ctensor' (component tensor) package which will
perform a coordinate transformation upon an arbitrary square
symmetric matrix <M>. The user must input the functions which
define the transformation.  (Formerly called transform'.)


Function: findde (<A>, <n>)

     returns a list of the unique differential equations (expressions)
corresponding to the elements of the <n> dimensional square array
<A>. Presently, <n> may be 2 or 3. deindex' is a global list
containing the indices of <A> corresponding to these unique
differential equations. For the Einstein tensor (ein'), which is
a two dimensional array, if computed for the metric in the example
below, findde' gives the following independent differential
equations:

(%o1)       /share/tensor/ctensor.mac
(%i2) derivabbrev:true;
(%o2)                                true
(%i3) dim:4;
(%o3)                                  4
(%i4) lg:matrix([a, 0, 0, 0], [ 0, x^2, 0, 0],
[0, 0, x^2*sin(y)^2, 0], [0,0,0,-d]);
[ a  0       0        0  ]
[                        ]
[     2                  ]
[ 0  x       0        0  ]
(%o4)                     [                        ]
[         2    2         ]
[ 0  0   x  sin (y)   0  ]
[                        ]
[ 0  0       0       - d ]
(%i5) depends([a,d],x);
(%o5)                            [a(x), d(x)]
(%i6) ct_coords:[x,y,z,t];
(%o6)                            [x, y, z, t]
(%i7) cmetric();
(%o7)                                done
(%i8) einstein(false);
(%o8)                                done
(%i9) findde(ein,2);
2
(%o9) [d  x - a d + d, 2 a d d    x - a (d )  x - a  d d  x
x                     x x         x        x    x

2          2
+ 2 a d d   - 2 a  d , a  x + a  - a]
x       x      x
(%i10) deindex;
(%o10)                     [[1, 1], [2, 2], [4, 4]]