<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>null-char-p</title><link rel="stylesheet" href="ecl.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.75.2"><link rel="home" href="index.html" title="The ECL manual"><link rel="up" href="rn01.html" title="Primitive Types"><link rel="prev" href="rn01re47.html" title="def-foreign-type"><link rel="next" href="rn02.html" title="Aggregate Types"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><code class="function">null-char-p</code></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="rn01re47.html">Prev</a> </td><th width="60%" align="center">Primitive Types</th><td width="20%" align="right"> <a accesskey="n" href="rn02.html">Next</a></td></tr></table><hr></div><div class="refentry" title="null-char-p"><a name="uffi.null-char-p"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p><code class="function">null-char-p</code> — Tests a character for <code class="constant">NULL</code> value.
</p></div><div class="refsynopsisdiv" title="Macro"><h2>Macro</h2><div class="funcsynopsis"><p><code class="funcdef">(null-char-p</code> <var class="pdparam">char</var>)</p></div><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><p><span class="term"><em class="parameter"><code>char</code></em></span></p></td><td><p>A character or integer.
</p></td></tr><tr><td><p><span class="term">returns</span></p></td><td><p>A boolean flag indicating if char is a <code class="constant">NULL</code> value.
</p></td></tr></tbody></table></div></div><div class="refsect1" title="Description"><a name="id685994"></a><h2>Description</h2><p>A predicate testing if a character or integer is <code class="constant">NULL</code>. This
abstracts the difference in implementations where some return a
<code class="computeroutput">character</code> and some return a
<code class="computeroutput">integer</code> whence dereferencing a
<code class="computeroutput">C</code> character pointer.
</p></div><div class="refsect1" title="Examples"><a name="id686026"></a><h2>Examples</h2><pre class="screen">
(def-array-pointer ca :unsigned-char)
(let ((fs (convert-to-foreign-string "ab")))
(values (null-char-p (deref-array fs 'ca 0))
(null-char-p (deref-array fs 'ca 2))))
=> <code class="constant">NIL</code>
<code class="constant">T</code></pre></div><div class="refsect1" title="Side Effects"><a name="id686046"></a><h2>Side Effects</h2><p>None.
</p></div><div class="refsect1" title="Affected by"><a name="id686056"></a><h2>Affected by</h2><p>None.</p></div><div class="refsect1" title="Exceptional Situations"><a name="id686066"></a><h2>Exceptional Situations</h2><p>None.</p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="rn01re47.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="rn01.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="rn02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><code class="function">def-foreign-type</code> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Aggregate Types</td></tr></table></div></body></html>
