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<a name="Character-Class-Functions"></a>
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<a name="Character-Class-Functions-1"></a>
<h3 class="section">5.7 Character Class Functions</h3>

<p>Octave also provides the following character class test functions
patterned after the functions in the standard C library.  They all
operate on string arrays and return matrices of zeros and ones.
Elements that are nonzero indicate that the condition was true for the
corresponding character in the string array.  For example:
</p>
<div class="example">
<pre class="example">isalpha (&quot;!Q@WERT^Y&amp;&quot;)
     &rArr; [ 0, 1, 0, 1, 1, 1, 1, 0, 1, 0 ]
</pre></div>

<a name="XREFisalnum"></a><dl>
<dt><a name="index-isalnum"></a>Mapping Function: <em></em> <strong>isalnum</strong> <em>(<var>s</var>)</em></dt>
<dd><p>Return a logical array which is true where the elements of <var>s</var> are
letters or digits and false where they are not.  This is equivalent to
(<code>isalpha (<var>s</var>) | isdigit (<var>s</var>)</code>).
</p>
<p><strong>See also:</strong> <a href="#XREFisalpha">isalpha</a>, <a href="#XREFisdigit">isdigit</a>, <a href="#XREFispunct">ispunct</a>, <a href="#XREFisspace">isspace</a>, <a href="#XREFiscntrl">iscntrl</a>.
</p></dd></dl>


<a name="XREFisalpha"></a><dl>
<dt><a name="index-isalpha"></a>Mapping Function: <em></em> <strong>isalpha</strong> <em>(<var>s</var>)</em></dt>
<dd><p>Return a logical array which is true where the elements of <var>s</var> are
letters and false where they are not.  This is equivalent to
(<code>islower (<var>s</var>) | isupper (<var>s</var>)</code>).
</p>
<p><strong>See also:</strong> <a href="#XREFisdigit">isdigit</a>, <a href="#XREFispunct">ispunct</a>, <a href="#XREFisspace">isspace</a>, <a href="#XREFiscntrl">iscntrl</a>, <a href="#XREFisalnum">isalnum</a>, <a href="#XREFislower">islower</a>, <a href="#XREFisupper">isupper</a>.
</p></dd></dl>


<a name="XREFisletter"></a><dl>
<dt><a name="index-isletter"></a>Function File: <em></em> <strong>isletter</strong> <em>(<var>s</var>)</em></dt>
<dd><p>Return a logical array which is true where the elements of <var>s</var>
are letters and false where they are not.  This is an alias for
the <code>isalpha</code> function.
</p>
<p><strong>See also:</strong> <a href="#XREFisalpha">isalpha</a>, <a href="#XREFisdigit">isdigit</a>, <a href="#XREFispunct">ispunct</a>, <a href="#XREFisspace">isspace</a>, <a href="#XREFiscntrl">iscntrl</a>, <a href="#XREFisalnum">isalnum</a>.
</p></dd></dl>


<a name="XREFislower"></a><dl>
<dt><a name="index-islower"></a>Mapping Function: <em></em> <strong>islower</strong> <em>(<var>s</var>)</em></dt>
<dd><p>Return a logical array which is true where the elements of <var>s</var> are
lowercase letters and false where they are not.
</p>
<p><strong>See also:</strong> <a href="#XREFisupper">isupper</a>, <a href="#XREFisalpha">isalpha</a>, <a href="#XREFisletter">isletter</a>, <a href="#XREFisalnum">isalnum</a>.
</p></dd></dl>


<a name="XREFisupper"></a><dl>
<dt><a name="index-isupper"></a>Mapping Function: <em></em> <strong>isupper</strong> <em>(<var>s</var>)</em></dt>
<dd><p>Return a logical array which is true where the elements of <var>s</var> are
uppercase letters and false where they are not.
</p>
<p><strong>See also:</strong> <a href="#XREFislower">islower</a>, <a href="#XREFisalpha">isalpha</a>, <a href="#XREFisletter">isletter</a>, <a href="#XREFisalnum">isalnum</a>.
</p></dd></dl>


<a name="XREFisdigit"></a><dl>
<dt><a name="index-isdigit"></a>Mapping Function: <em></em> <strong>isdigit</strong> <em>(<var>s</var>)</em></dt>
<dd><p>Return a logical array which is true where the elements of <var>s</var> are
decimal digits (0-9) and false where they are not.
</p>
<p><strong>See also:</strong> <a href="#XREFisxdigit">isxdigit</a>, <a href="#XREFisalpha">isalpha</a>, <a href="#XREFisletter">isletter</a>, <a href="#XREFispunct">ispunct</a>, <a href="#XREFisspace">isspace</a>, <a href="#XREFiscntrl">iscntrl</a>.
</p></dd></dl>


<a name="XREFisxdigit"></a><dl>
<dt><a name="index-isxdigit"></a>Mapping Function: <em></em> <strong>isxdigit</strong> <em>(<var>s</var>)</em></dt>
<dd><p>Return a logical array which is true where the elements of <var>s</var> are
hexadecimal digits (0-9 and a-fA-F).
</p>
<p><strong>See also:</strong> <a href="#XREFisdigit">isdigit</a>.
</p></dd></dl>


<a name="XREFispunct"></a><dl>
<dt><a name="index-ispunct"></a>Mapping Function: <em></em> <strong>ispunct</strong> <em>(<var>s</var>)</em></dt>
<dd><p>Return a logical array which is true where the elements of <var>s</var> are
punctuation characters and false where they are not.
</p>
<p><strong>See also:</strong> <a href="#XREFisalpha">isalpha</a>, <a href="#XREFisdigit">isdigit</a>, <a href="#XREFisspace">isspace</a>, <a href="#XREFiscntrl">iscntrl</a>.
</p></dd></dl>


<a name="XREFisspace"></a><dl>
<dt><a name="index-isspace"></a>Mapping Function: <em></em> <strong>isspace</strong> <em>(<var>s</var>)</em></dt>
<dd><p>Return a logical array which is true where the elements of <var>s</var> are
whitespace characters (space, formfeed, newline, carriage return, tab, and
vertical tab) and false where they are not.
</p>
<p><strong>See also:</strong> <a href="#XREFiscntrl">iscntrl</a>, <a href="#XREFispunct">ispunct</a>, <a href="#XREFisalpha">isalpha</a>, <a href="#XREFisdigit">isdigit</a>.
</p></dd></dl>


<a name="XREFiscntrl"></a><dl>
<dt><a name="index-iscntrl"></a>Mapping Function: <em></em> <strong>iscntrl</strong> <em>(<var>s</var>)</em></dt>
<dd><p>Return a logical array which is true where the elements of <var>s</var> are
control characters and false where they are not.
</p>
<p><strong>See also:</strong> <a href="#XREFispunct">ispunct</a>, <a href="#XREFisspace">isspace</a>, <a href="#XREFisalpha">isalpha</a>, <a href="#XREFisdigit">isdigit</a>.
</p></dd></dl>


<a name="XREFisgraph"></a><dl>
<dt><a name="index-isgraph"></a>Mapping Function: <em></em> <strong>isgraph</strong> <em>(<var>s</var>)</em></dt>
<dd><p>Return a logical array which is true where the elements of <var>s</var> are
printable characters (but not the space character) and false where they are
not.
</p>
<p><strong>See also:</strong> <a href="#XREFisprint">isprint</a>.
</p></dd></dl>


<a name="XREFisprint"></a><dl>
<dt><a name="index-isprint"></a>Mapping Function: <em></em> <strong>isprint</strong> <em>(<var>s</var>)</em></dt>
<dd><p>Return a logical array which is true where the elements of <var>s</var> are
printable characters (including the space character) and false where they
are not.
</p>
<p><strong>See also:</strong> <a href="#XREFisgraph">isgraph</a>.
</p></dd></dl>


<a name="XREFisascii"></a><dl>
<dt><a name="index-isascii"></a>Mapping Function: <em></em> <strong>isascii</strong> <em>(<var>s</var>)</em></dt>
<dd><p>Return a logical array which is true where the elements of <var>s</var> are
ASCII characters (in the range 0 to 127 decimal) and false where they are
not.
</p></dd></dl>


<a name="XREFisstrprop"></a><dl>
<dt><a name="index-isstrprop"></a>Function File: <em></em> <strong>isstrprop</strong> <em>(<var>str</var>, <var>prop</var>)</em></dt>
<dd><p>Test character string properties.  For example:
</p>
<div class="example">
<pre class="example">isstrprop (&quot;abc123&quot;, &quot;alpha&quot;)
&rArr; [1, 1, 1, 0, 0, 0]
</pre></div>

<p>If <var>str</var> is a cell array, <code>isstrpop</code> is applied recursively
to each element of the cell array.
</p>
<p>Numeric arrays are converted to character strings.
</p>
<p>The second argument <var>prop</var> must be one of
</p>
<dl compact="compact">
<dt><code>&quot;alpha&quot;</code></dt>
<dd><p>True for characters that are alphabetic (letters).
</p>
</dd>
<dt><code>&quot;alnum&quot;</code></dt>
<dt><code>&quot;alphanum&quot;</code></dt>
<dd><p>True for characters that are alphabetic or digits.
</p>
</dd>
<dt><code>&quot;lower&quot;</code></dt>
<dd><p>True for lowercase letters.
</p>
</dd>
<dt><code>&quot;upper&quot;</code></dt>
<dd><p>True for uppercase letters.
</p>
</dd>
<dt><code>&quot;digit&quot;</code></dt>
<dd><p>True for decimal digits (0-9).
</p>
</dd>
<dt><code>&quot;xdigit&quot;</code></dt>
<dd><p>True for hexadecimal digits (a-fA-F0-9).
</p>
</dd>
<dt><code>&quot;space&quot;</code></dt>
<dt><code>&quot;wspace&quot;</code></dt>
<dd><p>True for whitespace characters (space, formfeed, newline, carriage
return, tab, vertical tab).
</p>
</dd>
<dt><code>&quot;punct&quot;</code></dt>
<dd><p>True for punctuation characters (printing characters except space
or letter or digit).
</p>
</dd>
<dt><code>&quot;cntrl&quot;</code></dt>
<dd><p>True for control characters.
</p>
</dd>
<dt><code>&quot;graph&quot;</code></dt>
<dt><code>&quot;graphic&quot;</code></dt>
<dd><p>True for printing characters except space.
</p>
</dd>
<dt><code>&quot;print&quot;</code></dt>
<dd><p>True for printing characters including space.
</p>
</dd>
<dt><code>&quot;ascii&quot;</code></dt>
<dd><p>True for characters that are in the range of ASCII encoding.
</p>
</dd>
</dl>


<p><strong>See also:</strong> <a href="#XREFisalpha">isalpha</a>, <a href="#XREFisalnum">isalnum</a>, <a href="#XREFislower">islower</a>, <a href="#XREFisupper">isupper</a>, <a href="#XREFisdigit">isdigit</a>, <a href="#XREFisxdigit">isxdigit</a>, <a href="#XREFisspace">isspace</a>, <a href="#XREFispunct">ispunct</a>, <a href="#XREFiscntrl">iscntrl</a>, <a href="#XREFisgraph">isgraph</a>, <a href="#XREFisprint">isprint</a>, <a href="#XREFisascii">isascii</a>.
</p></dd></dl>



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