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<html><head><title>XLISP if</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="../examples/examples.htm">Examples</a> |
<a href="reference-index.htm">Reference</a>
<hr>
<h1>if</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>special form (fsubr)</nobr></td>
</tr>
<tr valign="top">
<td><nobr>Source:</nobr></td>
<td><nobr> - </nobr></td>
<td width="100%"><nobr>xlcont.c</nobr></td>
</tr>
</tbody></table></p>
<h2>Syntax</h2>
<dl>
<dt>(if <i>test-expr then-expr</i> [<i>else-expr</i>])</dt>
<dd><i>test-expr</i> - an expression<br>
<i>then-expr</i> - the THEN clause, an expression<br>
<i>else-expr</i> - the ELSE clause, an optional expression<br>
returns - the value of the selected expression</dd>
</dl>
<h2>Description</h2>
<p>The 'if' special form evaluates the 'test-expr'. If 'test-expr' evaluates
to a non-<a href="nil.htm">NIL</a> value, then 'then-expr' is
evaluated and returned as the result. If 'test-expr' evaluates to
<a href="nil.htm">NIL</a> and there is an 'else-expr', then the
'else-expr' is evaluated and its result is returned. If there is no
'else-expr' and 'test-expr' evaluates to
<nobr><a href="nil.htm">NIL</a> ,</nobr> then
<a href="nil.htm">NIL</a> is returned as a result.</p>
<h2>Examples</h2>
<pre class="example">
(if T (print "will print") <font color="#008844">; prints "will print"</font>
(print "won't print"))
(if NIL (print "won't print")
(print "will print")) <font color="#008844">; prints "will print"</font>
(if 'a T NIL) <font color="#008844">; returns T</font>
(if NIL 'nope 'yep) <font color="#008844">; returns YEP</font>
</pre>
<p>See the
<a href="../manual/xlisp-man-019.htm#if"> if </a>
special form in the <nobr>XLISP 2.0</nobr> manual.</p>
<p><nobr> <a href="#top">Back to Top</nobr></a></p>
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