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<html><head><title>XLISP eq</title>
<link rel="stylesheet" type="text/css" href="reference.css">
</head>
<body>
<a href="../start.htm">Nyquist / XLISP 2.0</a> -
<a href="../manual/contents.htm">Contents</a> |
<a href="../tutorials/tutorials.htm">Tutorials</a> |
<a href="../examples/examples.htm">Examples</a> |
<a href="reference-index.htm">Reference</a>
<hr>
<h1>eq</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>xllist.c, xlsubr.c</nobr></td>
</tr>
</tbody></table></p>
<h2>Syntax</h2>
<p><div class="box">
<dl>
<dt>(<b>eq</b> <i>expr1 expr2</i>)</dt>
<dd><i>exprN</i> - arbitrary Lisp expressions<br>
returns - <a href="t.htm"> T </a> if the expressions
eveluate to the same internal value, <a href="nil.htm">NIL</a>
otherwise</dd>
</dl>
</div></p>
<h2>Description</h2>
<p>Two expressions are 'eq' if the expressions are identical. <nobr>The 'eq'
function</nobr> tests if the results of the evaluated expressions point to
the same memory location. <a href="t.htm"> T </a> is returned if
both expressions evaluate to exactly the same internal value,
<a href="nil.htm">NIL</a> is returned otherwise.</p>
<p>Integer numbers being <a href="number-equal.htm"> = </a> are
'eq' as long as not stored in a CPU register, so the
<a href="eql.htm">eql</a> function is recommended for testing integers. Also
note that arrays, <nobr>floating-point</nobr> numbers, lists, and strings
are only 'eq' if they are bound as variable values to the same symbol.</p>
<h2>Examples</h2>
<pre class="example">
(eq 'a 'a) => T
(eq 1 1) => T or NIL
(eq 1 1.0) => NIL
(eq 1.0 1.0) => NIL
(eq "a" "a") => NIL
(eq '(a b) '(a b)) => NIL
(eq 'a 34) => NIL
(setq a '(a b)) <font color="#008844">; set value of A to (A B)</font>
(setq b a) <font color="#008844">; set B to point to A's value</font>
(setq c '(a b)) <font color="#008844">; set value of C to different (A B)</font>
(eq a b) => T
(eq a c) => NIL
</pre>
<p>See also <a href="eql.htm">eql</a>, <a href="equal.htm">equal</a>,
<nobr><a href="../examples/common-lisp/equalp.htm">cl:equalp</a></nobr>.</p>
<p><nobr> <a href="#top">Back to Top</nobr></a></p>
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<a href="../manual/contents.htm">Contents</a> |
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