docsrc/xlisp/xlisp-doc/reference/atom.htm


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<html><head><title>XLISP atom</title>

<link rel="stylesheet" type="text/css" href="reference.css">

<body>

<a href="../start.htm">Nyquist / XLISP 2.0</a>&nbsp; -&nbsp;
<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>atom</h1>

<hr>

<p><table cellpadding="0" cellspacing="0" style="margin-left:10px"><tbody>
<tr valign="top">
  <td><nobr>Type:</nobr></td>
  <td><nobr>&nbsp;&nbsp;-&nbsp;&nbsp;</nobr></td>
  <td width="100%"><nobr>predicate function (subr)</nobr></td>
</tr>
<tr valign="top">
  <td><nobr>Source:</nobr></td>
  <td><nobr>&nbsp;&nbsp;-&nbsp;&nbsp;</nobr></td>
  <td width="100%"><nobr>xlbfun.c</nobr></td>
</tr>
</tbody></table></p>

<h2>Syntax</h2>

<p><div class="box">

<dl>
<dt>(<b>atom</b> <i>expr</i>)</dt>
<dd><i>expr</i> - an arbitrary Lisp expression<br>
returns - <a href="t.htm">&nbsp;T&nbsp;</a> if the value is
an atom, <a href="nil.htm">NIL</a> otherwise</dd>
</dl>

</div></p>

<h2>Description</h2>

<p>The 'atom' predicate function tests if the 'expr' is an atom.
<a href="t.htm">&nbsp;T&nbsp;</a> is returned if 'expr' is an
atom, <a href="nil.htm">NIL</a> is returned otherwise.</p>

<h2>Examples</h2>

<pre class="example">
(atom 'a)                      =&gt; T   <font color="#008844">; symbol</font>
(atom #'atom)                  =&gt; T   <font color="#008844">; subr - function</font>
(atom "string")                =&gt; T   <font color="#008844">; string</font>
(atom 4)                       =&gt; T   <font color="#008844">; integer</font>
(atom 4.5)                     =&gt; T   <font color="#008844">; float</font>
(atom object)                  =&gt; T   <font color="#008844">; object</font>
(atom #(1 2 3))                =&gt; T   <font color="#008844">; array</font>
(atom #'quote)                 =&gt; T   <font color="#008844">; fsubr</font>
(atom *standard-output*)       =&gt; T   <font color="#008844">; stream</font>
(atom '())                     =&gt; T   <font color="#008844">; NIL is an atom</font>
(atom (lambda (x) (print x)))  =&gt; T   <font color="#008844">; closure</font>
(atom '(a b c))                =&gt; NIL <font color="#008844">; list</font>
(setq a '(a b))                =&gt; (A B)
(atom a)                       =&gt; NIL <font color="#008844">; value of A is not an atom</font>
</pre>

<p><b>Note:</b> <a href="nil.htm">NIL</a> or '() is used in many places as a
list or atom expression. Both 'atom' and <a href="listp.htm">listp</a>, when
applied to <a href="nil.htm">NIL</a>, return
<a href="t.htm">&nbsp;T&nbsp;</a>.</p>

<p>See also:</p>

<ul>
<li><nobr>Contents &rarr; <a href="../manual/contents.htm#predicate-functions">Predicate Functions</a></nobr></li>
</ul>

<p><nobr>&nbsp;&nbsp;<a href="#top">Back to Top</nobr></a></p>

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<a href="../manual/xlisp-man-index.htm">XLISP 2.0</a>&nbsp; -&nbsp;
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