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<h3 class="section">16.7 A Sample Function Definition</h3>

<p><a name="index-Function-definitions-989"></a><a name="index-Command-definitions-990"></a><a name="index-Macro-definitions-991"></a><a name="index-Sample-function-definition-992"></a>
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>Here is a definition from <a href="../elisp/Calling-Functions.html#Calling-Functions">Calling Functions</a>.

  <blockquote>

<div class="defun">
&mdash; Function: <b>apply</b><var> function &amp;rest arguments<a name="index-apply-993"></a></var><br>
<blockquote><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 <dfn>appended</dfn> to the other arguments.

       <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>.

     <pre class="example">          (setq f 'list)
              &rArr; list
          (apply f 'x 'y 'z)
          error--&gt; 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>
       <p>An interesting example of using <code>apply</code> is found in the description
of <code>mapcar</code>. 
</p></blockquote></div>
</blockquote>

  <p>In the Texinfo source file, this example looks like this:

<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.
     
     @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}.
     
     @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
     
     An interesting example of using @code{apply} is found
     in the description of @code{mapcar}.
     @end defun
</pre>
  <p class="noindent">In this manual, this function is listed in the Command and Variable
Index under <code>apply</code>.

  <p>Ordinary variables and user options are described using a format like
that for functions except that variables do not take arguments.

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