File: maxima_3.html

package info (click to toggle)
maxima 5.21.1-2squeeze
links: PTS
area: main
in suites: squeeze
size: 94,928 kB
ctags: 43,849
sloc: lisp: 298,974; fortran: 14,666; perl: 14,325; tcl: 10,494; sh: 4,052; makefile: 2,975; ansic: 471; awk: 24; sed: 7
file content (750 lines) | stat: -rw-r--r-- 29,147 bytes
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html401/loose.dtd">
<html>
<!-- Created on April, 24 2010 by texi2html 1.76 -->
<!--
Written by: Lionel Cons <Lionel.Cons@cern.ch> (original author)
            Karl Berry  <karl@freefriends.org>
            Olaf Bachmann <obachman@mathematik.uni-kl.de>
            and many others.
Maintained by: Many creative people <dev@texi2html.cvshome.org>
Send bugs and suggestions to <users@texi2html.cvshome.org>

-->
<head>
<title>Maxima 5.21.1 Manual: 3. Help</title>

<meta name="description" content="Maxima 5.21.1 Manual: 3. Help">
<meta name="keywords" content="Maxima 5.21.1 Manual: 3. Help">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="texi2html 1.76">
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<style type="text/css">
<!--
a.summary-letter {text-decoration: none}
pre.display {font-family: serif}
pre.format {font-family: serif}
pre.menu-comment {font-family: serif}
pre.menu-preformatted {font-family: serif}
pre.smalldisplay {font-family: serif; font-size: smaller}
pre.smallexample {font-size: smaller}
pre.smallformat {font-family: serif; font-size: smaller}
pre.smalllisp {font-size: smaller}
span.sansserif {font-family:sans-serif; font-weight:normal;}
ul.toc {list-style: none}
body
{
    color: black;
    background: white; 
    margin-left: 8%;
    margin-right: 13%;
}

h1
{
    margin-left: +8%;
    font-size: 150%;
    font-family: sans-serif
}

h2
{
    font-size: 125%;
    font-family: sans-serif
}

h3
{
    font-size: 100%;
    font-family: sans-serif
}

h2,h3,h4,h5,h6 { margin-left: +4%; }

div.textbox
{
    border: solid;
    border-width: thin;
    /* width: 100%; */
    padding-top: 1em;
    padding-bottom: 1em;
    padding-left: 2em;
    padding-right: 2em
}

div.titlebox
{
    border: none;
    padding-top: 1em;
    padding-bottom: 1em;
    padding-left: 2em;
    padding-right: 2em;
    background: rgb(200,255,255);
    font-family: sans-serif
}

div.synopsisbox
{
    border: none;
    padding-top: 1em;
    padding-bottom: 1em;
    padding-left: 2em;
    padding-right: 2em;
     background: rgb(255,220,255);
    /*background: rgb(200,255,255); */
    /* font-family: fixed */
}

pre.example
{
    border: 1px solid gray;
    padding-top: 1em;
    padding-bottom: 1em;
    padding-left: 1em;
    padding-right: 1em;
    /* background: rgb(247,242,180); */ /* kind of sandy */
    /* background: rgb(200,255,255); */ /* sky blue */
    background-color: #F1F5F9; /* light blue-gray */
    /* font-family: "Lucida Console", monospace */
}

div.spacerbox
{
    border: none;
    padding-top: 2em;
    padding-bottom: 2em
}

div.image
{
    margin: 0;
    padding: 1em;
    text-align: center;
}

div.categorybox
{
    border: 1px solid gray;
    padding-top: 0px;
    padding-bottom: 0px;
    padding-left: 1em;
    padding-right: 1em;
    background: rgb(247,242,220);
}


-->
</style>

<link rel="icon" href="http://maxima.sourceforge.net/favicon.ico"/>
</head>

<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">

<a name="Help"></a>
<a name="SEC4"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="maxima_2.html#SEC3" title="Previous section in reading order"> &lt; </a>]</td>
<td valign="middle" align="left">[<a href="#SEC5" title="Next section in reading order"> &gt; </a>]</td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left">[<a href="maxima_2.html#SEC2" title="Beginning of this chapter or previous chapter"> &lt;&lt; </a>]</td>
<td valign="middle" align="left">[<a href="maxima.html#SEC_Top" title="Up section"> Up </a>]</td>
<td valign="middle" align="left">[<a href="maxima_4.html#SEC9" title="Next chapter"> &gt;&gt; </a>]</td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left">[<a href="maxima.html#SEC_Top" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="maxima_toc.html#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="maxima_79.html#SEC331" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="maxima_abt.html#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<h1 class="chapter"> 3. Help </h1>

<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#SEC5">3.1 Lisp and Maxima</a></td><td>&nbsp;&nbsp;</td><td align="left" valign="top">            
</td></tr>
<tr><td align="left" valign="top"><a href="#SEC6">3.2 Garbage Collection</a></td><td>&nbsp;&nbsp;</td><td align="left" valign="top">          
</td></tr>
<tr><td align="left" valign="top"><a href="#SEC7">3.3 Documentation</a></td><td>&nbsp;&nbsp;</td><td align="left" valign="top">               
</td></tr>
<tr><td align="left" valign="top"><a href="#SEC8">3.4 Functions and Variables for Help</a></td><td>&nbsp;&nbsp;</td><td align="left" valign="top">        
</td></tr>
</table>

<p><a name="Item_003a-Lisp-and-Maxima"></a>
</p><hr size="6">
<a name="Lisp-and-Maxima"></a>
<a name="SEC5"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#SEC4" title="Previous section in reading order"> &lt; </a>]</td>
<td valign="middle" align="left">[<a href="#SEC6" title="Next section in reading order"> &gt; </a>]</td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left">[<a href="#SEC4" title="Beginning of this chapter or previous chapter"> &lt;&lt; </a>]</td>
<td valign="middle" align="left">[<a href="#SEC4" title="Up section"> Up </a>]</td>
<td valign="middle" align="left">[<a href="maxima_4.html#SEC9" title="Next chapter"> &gt;&gt; </a>]</td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left">[<a href="maxima.html#SEC_Top" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="maxima_toc.html#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="maxima_79.html#SEC331" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="maxima_abt.html#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<h2 class="section"> 3.1 Lisp and Maxima </h2>
<p>Maxima is written in Lisp, and it is easy to access Lisp functions and variables
from Maxima and vice versa.
Lisp and Maxima symbols are distinguished by a naming convention.
A Lisp symbol which begins with a dollar sign <code>$</code> corresponds to
a Maxima symbol without the dollar sign.
A Maxima symbol which begins with a question mark <code>?</code> corresponds to
a Lisp symbol without the question mark.
For example, the Maxima symbol <code>foo</code> corresponds to the Lisp symbol <code>$foo</code>,
while the Maxima symbol <code>?foo</code> corresponds to the Lisp symbol <code>foo</code>,
Note that <code>?foo</code> is written without a space between <code>?</code> and <code>foo</code>;
otherwise it might be mistaken for <code>describe (&quot;foo&quot;)</code>.
</p>
<p>Hyphen <code>-</code>, asterisk <code>*</code>, or other special characters in Lisp symbols
must be escaped by backslash <code>\</code> where they appear in Maxima code.
For example, the Lisp identifier <code>*foo-bar*</code> is written <code>?\*foo\-bar\*</code> in Maxima.
</p>
<p>Lisp code may be executed from within a Maxima session.
A single line of Lisp (containing one or more forms) may be executed
by the special command <code>:lisp</code>. For example,
</p>
<pre class="example">(%i1) :lisp (foo $x $y)
</pre>

<p>calls the Lisp function <code>foo</code> with Maxima variables <code>x</code> and <code>y</code> as arguments.
The <code>:lisp</code> construct can appear at the interactive prompt
or in a file processed by <code>batch</code> or <code>demo</code>, but not in a file processed by
<code>load</code>, <code>batchload</code>, <code>translate_file</code>, or <code>compile_file</code>.
</p>
<p>The function <code>to_lisp()</code> opens an interactive Lisp session.
Entering <code>(to-maxima)</code> closes the Lisp session and returns to Maxima.
</p>
<p>Lisp functions and variables which are to be visible in Maxima as
functions and variables with ordinary names (no special punctuation)
must have Lisp names beginning with the dollar sign <code>$</code>.
</p>
<p>Maxima is case-sensitive, distinguishing between lowercase and uppercase letters
in identifiers, while Lisp is not.
There are some rules governing the translation of names between Lisp and Maxima.
</p>
<ol>
<li>
A Lisp identifier not enclosed in vertical bars corresponds to a Maxima identifier
in lowercase.
Whether the Lisp identifier is uppercase, lowercase, or mixed case, is ignored.
E.g., Lisp <code>$foo</code>, <code>$FOO</code>, and <code>$Foo</code> all correspond to Maxima <code>foo</code>.
</li><li>
A Lisp identifier which is all uppercase or all lowercase
and enclosed in vertical bars corresponds to a Maxima identifier with case reversed.
That is, uppercase is changed to lowercase and lowercase to uppercase.
E.g., Lisp <code>|$FOO|</code> and <code>|$foo|</code>
correspond to Maxima <code>foo</code> and <code>FOO</code>, respectively.
</li><li>
A Lisp identifier which is mixed uppercase and lowercase
and enclosed in vertical bars corresponds to a Maxima identifier with the same case.
E.g., Lisp <code>|$Foo|</code> corresponds to Maxima <code>Foo</code>.
</li></ol>

<p>The <code>#$</code> Lisp macro allows the use of Maxima expressions in Lisp code.
<code>#$<var>expr</var>$</code> expands to a Lisp expression equivalent to the Maxima expression <var>expr</var>.
</p>
<pre class="example">(msetq $foo #$[x, y]$)
</pre>

<p>This has the same effect as entering
</p>
<pre class="example">(%i1) foo: [x, y];
</pre>

<p>The Lisp function <code>displa</code> prints an expression in Maxima format.
</p>
<pre class="example">(%i1) :lisp #$[x, y, z]$ 
((MLIST SIMP) $X $Y $Z)
(%i1) :lisp (displa '((MLIST SIMP) $X $Y $Z))
[x, y, z]
NIL
</pre>
<p>Functions defined in Maxima are not ordinary Lisp functions.
The Lisp function <code>mfuncall</code> calls a Maxima function.
For example:
</p>
<pre class="example">(%i1) foo(x,y) := x*y$
(%i2) :lisp (mfuncall '$foo 'a 'b)
((MTIMES SIMP) A B)
</pre>
<p>Some Lisp functions are shadowed in the Maxima package, namely the following.
</p>
<p><code>complement</code>,
<code>continue</code>,
<code>//</code>,
<code>float</code>,
<code>functionp</code>,
<code>array</code>,
<code>exp</code>,
<code>listen</code>,
<code>signum</code>,
<code>atan</code>,
<code>asin</code>,
<code>acos</code>,
<code>asinh</code>,
<code>acosh</code>,
<code>atanh</code>,
<code>tanh</code>,
<code>cosh</code>,
<code>sinh</code>,
<code>tan</code>,
<code>break</code>,
and <code>gcd</code>.
</p>
<div class=categorybox>


<p>Categories:&nbsp;&nbsp;<a href="maxima_95.html#Category_003a-Programming">Programming</a>
</p>
</div>


<p><a name="Item_003a-Garbage-Collection"></a>
</p><hr size="6">
<a name="Garbage-Collection"></a>
<a name="SEC6"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#SEC5" title="Previous section in reading order"> &lt; </a>]</td>
<td valign="middle" align="left">[<a href="#SEC7" title="Next section in reading order"> &gt; </a>]</td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left">[<a href="#SEC4" title="Beginning of this chapter or previous chapter"> &lt;&lt; </a>]</td>
<td valign="middle" align="left">[<a href="#SEC4" title="Up section"> Up </a>]</td>
<td valign="middle" align="left">[<a href="maxima_4.html#SEC9" title="Next chapter"> &gt;&gt; </a>]</td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left">[<a href="maxima.html#SEC_Top" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="maxima_toc.html#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="maxima_79.html#SEC331" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="maxima_abt.html#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<h2 class="section"> 3.2 Garbage Collection </h2>
<p>Symbolic computation tends to create a good deal
of garbage, and effective handling of this can be crucial to successful
completion of some programs.
</p>
<p>Under GCL, on UNIX systems where the mprotect system call is available
(including SUN OS 4.0 and some variants of BSD) a stratified garbage collection
is available.   This limits the collection to pages which have been recently
written to.    See the GCL documentation under ALLOCATE and GBC.   At the
Lisp level doing (setq si::*notify-gbc* t) will help you determine which
areas might need more space.
</p>
<p><a name="Item_003a-Documentation"></a>
</p><hr size="6">
<a name="Documentation"></a>
<a name="SEC7"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#SEC6" title="Previous section in reading order"> &lt; </a>]</td>
<td valign="middle" align="left">[<a href="#SEC8" title="Next section in reading order"> &gt; </a>]</td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left">[<a href="#SEC4" title="Beginning of this chapter or previous chapter"> &lt;&lt; </a>]</td>
<td valign="middle" align="left">[<a href="#SEC4" title="Up section"> Up </a>]</td>
<td valign="middle" align="left">[<a href="maxima_4.html#SEC9" title="Next chapter"> &gt;&gt; </a>]</td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left">[<a href="maxima.html#SEC_Top" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="maxima_toc.html#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="maxima_79.html#SEC331" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="maxima_abt.html#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<h2 class="section"> 3.3 Documentation </h2>


<p>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 <code>?</code> command (i.e., the <code>describe</code> function).
The user's manual is viewed as <code>info</code> hypertext by the <code>info</code> viewer program
and as a web page by any ordinary web browser.
</p>
<p><code>example</code> displays examples for many Maxima functions.
For example,
</p>
<pre class="example">(%i1) example (integrate);
</pre>
<p>yields
</p>
<pre class="example">(%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
</pre>
<p>and additional output.
</p>
<div class=categorybox>


<p>Categories:&nbsp;&nbsp;<a href="maxima_95.html#Category_003a-Console-interaction">Console interaction</a>
</p>
</div>


<p><a name="Item_003a-Functions-and-Variables-for-Help"></a>
</p><hr size="6">
<a name="Functions-and-Variables-for-Help"></a>
<a name="SEC8"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#SEC7" title="Previous section in reading order"> &lt; </a>]</td>
<td valign="middle" align="left">[<a href="maxima_4.html#SEC9" title="Next section in reading order"> &gt; </a>]</td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left">[<a href="#SEC4" title="Beginning of this chapter or previous chapter"> &lt;&lt; </a>]</td>
<td valign="middle" align="left">[<a href="#SEC4" title="Up section"> Up </a>]</td>
<td valign="middle" align="left">[<a href="maxima_4.html#SEC9" title="Next chapter"> &gt;&gt; </a>]</td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left">[<a href="maxima.html#SEC_Top" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="maxima_toc.html#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="maxima_79.html#SEC331" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="maxima_abt.html#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<h2 class="section"> 3.4 Functions and Variables for Help </h2>

<p><a name="Item_003a-apropos"></a>
</p><dl>
<dt><u>Function:</u> <b>apropos</b><i> (<var>string</var>)</i>
<a name="IDX5"></a>
</dt>
<dd><p>Searches for Maxima names which have <var>string</var> appearing anywhere within
them.  Thus, <code>apropos (exp)</code> returns a list of all the flags and functions
which have <code>exp</code> as part of their names, such as <code>expand</code>, <code>exp</code>,
and <code>exponentialize</code>.  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 <code>apropos (tr_)</code> to find a list of many of the switches relating
to the translator, most of which begin with <code>tr_</code>.
</p>
<p><code>apropos(&quot;&quot;)</code> returns a list with all Maxima names. 
</p>
<p><code>apropos</code> returns the empty list <code>[]</code>, if no name is found.
</p>
<p>Example:
</p>
<p>Show all Maxima symbols wich have <code>&quot;gamma&quot;</code> in the name:
</p>
<pre class="example">(%i1) apropos(&quot;gamma&quot;);
(%o1) [%gamma, %gammagreek, gamma, gammagreek, gammalim, gamma_expand, 
gamma_imag, gamma_incomplete, gamma_incomplete_generalized, 
gamma_incomplete_regularized, gamma_radius, Gamma, log_gamma, makegamma, 
gamma_incomplete_generalized_regularized]
</pre>
<div class=categorybox>


<p>Categories:&nbsp;&nbsp;<a href="maxima_95.html#Category_003a-Help">Help</a>
</p>
</div>

</dd></dl>

<p><a name="Item_003a-demo"></a>
</p><dl>
<dt><u>Function:</u> <b>demo</b><i> (<var>filename</var>)</i>
<a name="IDX6"></a>
</dt>
<dd><p>Evaluates Maxima expressions in <var>filename</var> and displays the results.
<code>demo</code> pauses after evaluating each expression
and continues after the user enters a carriage return.
(If running in Xmaxima, <code>demo</code> may need to see a semicolon <code>;</code>
followed by a carriage return.)
</p>
<p><code>demo</code> searches the list of directories
<code>file_search_demo</code> to find <code>filename</code>.
If the file has the suffix <code>dem</code>,
the suffix may be omitted.
See also <code>file_search</code>.
</p>
<p><code>demo</code> evaluates its argument.
<code>demo</code> returns the name of the demonstration file.
</p>
<p>Example:
</p>
<pre class="example">(%i1) demo (&quot;disol&quot;);

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)

_
(%i5) demo (&quot;rncomb&quot;);

batching /home/wfs/maxima/share/simplification/rncomb.dem
 At the _ prompt, type ';' followed by enter to get next demo
(%i6)                     load(rncomb)

_
                             z         x
(%i7)               exp1 : ----- + ---------
                           y + x   2 (y + x)
                          z         x
(%o7)                   ----- + ---------
                        y + x   2 (y + x)

_
(%i8)                     combine(exp1)
                          z         x
(%o8)                   ----- + ---------
                        y + x   2 (y + x)

_
(%i9)                     rncombine(%)
                             2 z + x
(%o9)                       ---------
                            2 (y + x)

_
                             d   c   b   a
(%i10)                exp2 : - + - + - + -
                             3   3   2   2
                          d   c   b   a
(%o10)                    - + - + - + -
                          3   3   2   2

_
(%i11)                    combine(exp2)
                      2 d + 2 c + 3 (b + a)
(%o11)                ---------------------
                                6

_
(%i12)                   rncombine(exp2)
                      2 d + 2 c + 3 b + 3 a
(%o12)                ---------------------
                                6

_
(%i13) 
</pre>
<div class=categorybox>


<p>Categories:&nbsp;&nbsp;<a href="maxima_95.html#Category_003a-Help">Help</a>
 &middot;
<a href="maxima_95.html#Category_003a-Console-interaction">Console interaction</a>
 &middot;
<a href="maxima_95.html#Category_003a-File-input">File input</a>
</p>
</div>


</dd></dl>

<p><a name="Item_003a-describe"></a>
</p><dl>
<dt><u>Function:</u> <b>describe</b><i> (<var>string</var>)</i>
<a name="IDX7"></a>
</dt>
<dt><u>Function:</u> <b>describe</b><i> (<var>string</var>, exact)</i>
<a name="IDX8"></a>
</dt>
<dt><u>Function:</u> <b>describe</b><i> (<var>string</var>, inexact)</i>
<a name="IDX9"></a>
</dt>
<dd><p><code>describe(<var>string</var>)</code> is equivalent to <code>describe(<var>string</var>, exact)</code>.
</p>
<p><code>describe(<var>string</var>, exact)</code> finds an item with title equal
(case-insensitive)
to <var>string</var>, if there is any such item.
</p>
<p><code>describe(<var>string</var>, inexact)</code> finds all documented items which contain <var>string</var> in their titles.
If there is more than one such item, Maxima asks the user to select
an item or items to display.
</p>
<p>At the interactive prompt,
<code>? foo</code> (with a space between <code>?</code> and <code>foo</code>)
is equivalent to <code>describe(&quot;foo&quot;, exact)</code>,
and <code>?? foo</code> is equivalent to <code>describe(&quot;foo&quot;, inexact)</code>.
</p>
<p><code>describe(&quot;&quot;, inexact)</code> yields a list of all topics documented in the on-line manual.
</p>
<p><code>describe</code> quotes its argument.
<code>describe</code> returns <code>true</code> if some documentation is found, otherwise <code>false</code>.
</p>
<p>See also <a href="#SEC7">Documentation</a>.
</p>
<p>Example:
</p>
<pre class="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 (&lt;expr&gt;, &lt;x&gt;)
 -- Function: integrate (&lt;expr&gt;, &lt;x&gt;, &lt;a&gt;, &lt;b&gt;)
     Attempts to symbolically compute the integral of &lt;expr&gt; with
     respect to &lt;x&gt;.  `integrate (&lt;expr&gt;, &lt;x&gt;)' is an indefinite
     integral, while `integrate (&lt;expr&gt;, &lt;x&gt;, &lt;a&gt;, &lt;b&gt;)' 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.
     [...]
</pre>
<p>In this example, items 7 and 8 were selected 
(output is shortened as indicated by <code>[...]</code>.
All or none of the items could have been selected by entering <code>all</code> or <code>none</code>,
which can be abbreviated <code>a</code> or <code>n</code>, respectively.
</p>
<div class=categorybox>


<p>Categories:&nbsp;&nbsp;<a href="maxima_95.html#Category_003a-Help">Help</a>
 &middot;
<a href="maxima_95.html#Category_003a-Console-interaction">Console interaction</a>
</p>
</div>

</dd></dl>

<p><a name="Item_003a-example"></a>
</p><dl>
<dt><u>Function:</u> <b>example</b><i> (<var>topic</var>)</i>
<a name="IDX10"></a>
</dt>
<dt><u>Function:</u> <b>example</b><i> ()</i>
<a name="IDX11"></a>
</dt>
<dd><p><code>example (<var>topic</var>)</code> displays some examples of <var>topic</var>, which is a
symbol or a string. To get examples for operators like <code>if</code>, <code>do</code>, or
<code>lambda</code> the argument must be a string, e.g. <code>example (&quot;do&quot;)</code>. 
<code>example</code> is not case sensitive. Most topics are function names.
</p>
<p><code>example ()</code> returns the list of all recognized topics.
</p>
<p>The name of the file containing the examples is given by the global option 
variable <code>manual_demo</code>, which defaults to <code>&quot;manual.demo&quot;</code>.
</p>
<p><code>example</code> quotes its argument. <code>example</code> returns <code>done</code> unless
no examples are found or there is no argument, in which case <code>example</code>
returns the list of all recognized topics.
</p>
<p>Examples:
</p>
<pre class="example">(%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(&quot;lambda&quot;);
(%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
(%i7) example(&quot;allROOTS&quot;);
(%i8) (1+2*x)^3 = 13.5*(1+x^5)
                                   3          5
(%o8)                     (2 x + 1)  = 13.5 (x  + 1)
(%i9) allroots(%)
(%o9) [x = .8296749902129361, x = - 1.015755543828121, 
x = .9659625152196369 %i - .4069597231924075, 
x = - .9659625152196369 %i - .4069597231924075, x = 1.0]
(%o9)                                done
</pre>
<div class=categorybox>


<p>Categories:&nbsp;&nbsp;<a href="maxima_95.html#Category_003a-Help">Help</a>
 &middot;
<a href="maxima_95.html#Category_003a-Console-interaction">Console interaction</a>
</p>
</div>

</dd></dl>

<p><a name="Item_003a-manual_005fdemo"></a>
</p><dl>
<dt><u>Option variable:</u> <b>manual_demo</b>
<a name="IDX12"></a>
</dt>
<dd><p>Default value: <code>&quot;manual.demo&quot;</code>
</p>
<p><code>manual_demo</code> specifies the name of the file containing the examples for 
the function <code>example</code>. See <code>example</code>.
</p>
<div class=categorybox>


<p>Categories:&nbsp;&nbsp;<a href="maxima_95.html#Category_003a-Help">Help</a>
 &middot;
<a href="maxima_95.html#Category_003a-Global-variables">Global variables</a>
</p>
</div>

</dd></dl>


<p><a name="Item_003a-Command-Line"></a>
</p><hr size="6">
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#SEC4" title="Beginning of this chapter or previous chapter"> &lt;&lt; </a>]</td>
<td valign="middle" align="left">[<a href="maxima_4.html#SEC9" title="Next chapter"> &gt;&gt; </a>]</td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left"> &nbsp; </td>
<td valign="middle" align="left">[<a href="maxima.html#SEC_Top" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="maxima_toc.html#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="maxima_79.html#SEC331" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="maxima_abt.html#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<p>
 <font size="-1">
  This document was generated by <em>Robert Dodier</em> on <em>April, 24 2010</em> using <a href="http://texi2html.cvshome.org/"><em>texi2html 1.76</em></a>.
 </font>
 <br>

</p>
</body>
</html>