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<title>Sample Function Definition (GNU Texinfo 6.7)</title>

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<span id="Sample-Function-Definition"></span><div class="header">
<p>
Previous: <a href="Def-Cmd-Conventions.html" accesskey="p" rel="prev">Def Cmd Conventions</a>, Up: <a href="Definition-Commands.html" accesskey="u" rel="up">Definition Commands</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Command-and-Variable-Index.html" title="Index" rel="index">Index</a>]</p>
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<hr>
<span id="A-Sample-Function-Definition"></span><h3 class="section">14.7 A Sample Function Definition</h3>
<span id="index-Function-definitions"></span>
<span id="index-Command-definitions"></span>
<span id="index-Macro-definitions_002c-programming_002dlanguage"></span>
<span id="index-Sample-function-definition"></span>

<p>A function definition uses the <code>@defun</code> and <code>@end defun</code>
commands.  The name of the function follows immediately after the
<code>@defun</code> command and it is followed, on the same line, by the
parameter list.
</p>
<p>Here is a definition from <a href="../elisp/Calling-Functions.html#Calling-Functions">Calling Functions</a> in <cite>The GNU Emacs
Lisp Reference Manual</cite>.
</p>
<blockquote>
<dl>
<dt id="index-apply">Function: <strong>apply</strong> <em>function &amp;rest arguments</em></dt>
<dd><p><code>apply</code> calls <var>function</var> with <var>arguments</var>, just
like <code>funcall</code> but with one difference: the last of
<var>arguments</var> is a list of arguments to give to
<var>function</var>, rather than a single argument.  We also say
that this list is <em>appended</em> to the other arguments.
</p>
<p><code>apply</code> returns the result of calling <var>function</var>.
As with <code>funcall</code>, <var>function</var> must either be a Lisp
function or a primitive function; special forms and macros
do not make sense in <code>apply</code>.
</p>
<div class="example">
<pre class="example">(setq f 'list)
    &rArr; list
(apply f 'x 'y 'z)
error&rarr; Wrong type argument: listp, z
(apply '+ 1 2 '(3 4))
    &rArr; 10
(apply '+ '(1 2 3 4))
    &rArr; 10

(apply 'append '((a b c) nil (x y z) nil))
    &rArr; (a b c x y z)
</pre></div>

<p>An interesting example of using <code>apply</code> is found in the description
of <code>mapcar</code>.
</p></dd></dl>
</blockquote>

<p>In the Texinfo source file, this example looks like this:
</p>
<div class="example">
<pre class="example">@defun apply function &amp;rest arguments
@code{apply} calls @var{function} with
@var{arguments}, just like @code{funcall} but with one
difference: the last of @var{arguments} is a list of
arguments to give to @var{function}, rather than a single
argument.  We also say that this list is @dfn{appended}
to the other arguments.
</pre><pre class="example">

</pre><pre class="example">@code{apply} returns the result of calling
@var{function}.  As with @code{funcall},
@var{function} must either be a Lisp function or a
primitive function; special forms and macros do not make
sense in @code{apply}.
</pre><pre class="example">

</pre><pre class="example">@example
(setq f 'list)
    @result{} list
(apply f 'x 'y 'z)
@error{} Wrong type argument: listp, z
(apply '+ 1 2 '(3 4))
    @result{} 10
(apply '+ '(1 2 3 4))
    @result{} 10

(apply 'append '((a b c) nil (x y z) nil))
    @result{} (a b c x y z)
@end example
</pre><pre class="example">

</pre><pre class="example">An interesting example of using @code{apply} is found
in the description of @code{mapcar}.
@end defun
</pre></div>

<p>In this manual, this function is listed in the Command and Variable
Index under <code>apply</code>.
</p>
<p>Ordinary variables and user options are described using a format like
that for functions except that variables do not take arguments.
</p>

<hr>
<div class="header">
<p>
Previous: <a href="Def-Cmd-Conventions.html" accesskey="p" rel="prev">Def Cmd Conventions</a>, Up: <a href="Definition-Commands.html" accesskey="u" rel="up">Definition Commands</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Command-and-Variable-Index.html" title="Index" rel="index">Index</a>]</p>
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