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<html><head><title>XLISP &aux</title>
<link rel="stylesheet" type="text/css" href="reference.css">
</head>
<body>
<a href="../start.htm">Nyquist / XLISP 2.0</a> -
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<a href="reference-index.htm">Reference</a>
<hr>
<h1>&aux</h1>
<hr>
<p><table cellpadding="0" cellspacing="0" style="margin-left:10px"><tbody>
<tr valign="top">
<td><nobr>Type:</nobr></td>
<td><nobr> - </nobr></td>
<td width="100%"><nobr>keyword</nobr></td>
</tr>
<tr valign="top">
<td><nobr>Source:</nobr></td>
<td><nobr> - </nobr></td>
<td width="100%"><nobr>xleval.c</nobr></td>
</tr>
</tbody></table></p>
<h2>Syntax</h2>
<p><div class="box">
<dl>
<dt><b>&aux</b> [<i>aux-var</i> | (<i>aux-var aux-value</i>)] ...</dt>
<dd><i>aux-var</i> - auxiliary variable<br>
<i>aux-value</i> - auxiliary variable initialization</dd>
</dl>
</div></p>
<h2>Description</h2>
<p> In XLISP, there are several times that you define a formal argument list
for a body of code [like <a href="defun.htm">defun</a>,
<a href="defmacro.htm">defmacro</a>,
<a href="keyword-answer.htm">:answer</a> and <a
href="lambda.htm">lambda</a>]. <nobr>The 'aux-var'</nobr> variables are a
mechanism for you to define variables local to the function or operation
definition. <nobr>If there</nobr> is an optional <nobr>'aux-value'</nobr>,
they will be set to that value on entry to the body of code. Otherwise, they
are initialized <nobr>to <a href="nil.htm">NIL</a></nobr>. <nobr>At
the</nobr> end of the function or operation execution, these local symbols
and their values are removed.</p>
<h2>Examples</h2>
<p>A function '<nobr>my-add</nobr>' with <nobr>one required</nobr> argument
'num1', <nobr>one <a href="lambda-keyword-rest.htm">&rest</a></nobr>
argument <nobr>'num-list'</nobr>, and <nobr>one &aux</nobr>
<nobr>variable 'sum'</nobr>:</p>
<pre class="example">
(defun my-add (num1 &rest num-list &aux sum)
(setq sum num1) <font color="#008844">; initialize SUM</font>
(dolist (i num-list) <font color="#008844">; loop through the num-list</font>
(setq sum (+ sum i))) <font color="#008844">; add each number to SUM</font>
sum) <font color="#008844">; return SUM when finished</font>
(my-add 1 2 3 4) => 10
(my-add 5 5 5 5 5) => 25
</pre>
<p>See <nobr><a href="addition.htm"> + </a></nobr>,
<a href="defun.htm">defun</a>, <a href="dolist.htm">dolist</a>,
<a href="lambda-keyword-rest.htm">&rest</a>,
<a href="setq.htm">setq</a>.</p>
<p>A function '<nobr>more-keys</nobr>' with <nobr>one required</nobr>
<nobr>argument 'a'</nobr> and <nobr>three &aux</nobr> variables <nobr>'b'
[initialized</nobr> <nobr>to <a href="nil.htm">NIL</a>]</nobr>, <nobr>'c'
[initialized</nobr> <nobr>to 99]</nobr>, and <nobr>'d' [initialized</nobr>
<nobr>to <a href="t.htm"> T </a>]</nobr>:</p>
<pre class="example">
(defun more-keys (a &aux b (c 99) (d t))
(format t "a=~a b=~a c=~a d=~a~%" a b c d))
> (more-keys "hi")
a=hi b=NIL c=99 d=T
NIL
</pre>
<p>See <a href="defun.htm">defun</a>, <a href="format.htm">format</a>.</p>
<p>See also:</p>
<ul>
<li><nobr><a href="../manual/xlisp.htm#auxiliary-variables">Auxiliary Variables</a></nobr></li>
</ul>
<p><nobr> <a href="#top">Back to Top</nobr></a></p>
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