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<html><head><title>XLISP zerop</title>
<link rel="stylesheet" type="text/css" href="reference.css">
</head>
<body>
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<hr>
<h1>zerop</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>predicate function (subr)</nobr></td>
</tr>
<tr valign="top">
<td><nobr>Source:</nobr></td>
<td><nobr> - </nobr></td>
<td width="100%"><nobr>xlmath.c</nobr></td>
</tr>
</tbody></table></p>
<h2>Syntax</h2>
<dl>
<dt>(zerop <i>expr</i>)</dt>
<dd><i>expr</i> - the numeric expression to check<br>
returns - <a href="t.htm"> T </a> if the number is
zero, <a href="nil.htm">NIL</a> otherwise</dd>
</dl>
<h2>Description</h2>
<p>The 'zerop' predicate function checks to see if the number 'expr' is
zero. <a href="t.htm"> T </a> is returned if the
number is zero, <a href="nil.htm">NIL</a> is returned otherwise.
An error is generated if the 'expr' is not a numeric expression:</p>
<pre class="example">
<font color="#AA0000">error: bad argument type</font>
</pre>
<h2>Examples</h2>
<pre class="example">
(zerop 0) <font color="#008844">; returns T</font>
(zerop 0.0) <font color="#008844">; returns T</font>
(zerop 99999.9) <font color="#008844">; returns NIL</font>
(zerop -0.000000000002) <font color="#008844">; returns NIL</font>
(zerop 'a) <font color="#008844">; error: bad argument type</font>
(setq a 0) <font color="#008844">; set value of A to 0</font>
(zerop a) <font color="#008844">; returns T</font>
</pre>
<p>See the
<a href="../manual/xlisp-man-018.htm#zerop">zerop</a>
predicate function in the <nobr>XLISP 2.0</nobr> manual.</p>
<p><nobr> <a href="#top">Back to Top</nobr></a></p>
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