/usr/share/doc/octave/octave.html/Function-Handles.html

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<a name="Function-Handles"></a>
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<p>
Next: <a href="Anonymous-Functions.html#Anonymous-Functions" accesskey="n" rel="next">Anonymous Functions</a>, Up: <a href="Function-Handles-Anonymous-Functions-Inline-Functions.html#Function-Handles-Anonymous-Functions-Inline-Functions" accesskey="u" rel="up">Function Handles Anonymous Functions Inline Functions</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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<hr>
<a name="Function-Handles-1"></a>
<h4 class="subsection">11.11.1 Function Handles</h4>

<p>A function handle is a pointer to another function and is defined with
the syntax
</p>
<div class="example">
<pre class="example">@<var>function-name</var>
</pre></div>

<p>For example,
</p>
<div class="example">
<pre class="example">f = @sin;
</pre></div>

<p>creates a function handle called <code>f</code> that refers to the
function <code>sin</code>.
</p>
<p>Function handles are used to call other functions indirectly, or to pass
a function as an argument to another function like <code>quad</code> or
<code>fsolve</code>.  For example:
</p>
<div class="example">
<pre class="example">f = @sin;
quad (f, 0, pi)
    &rArr; 2
</pre></div>

<p>You may use <code>feval</code> to call a function using function handle, or
simply write the name of the function handle followed by an argument
list.  If there are no arguments, you must use an empty argument list
&lsquo;<samp>()</samp>&rsquo;.  For example:
</p>
<div class="example">
<pre class="example">f = @sin;
feval (f, pi/4)
    &rArr; 0.70711
f (pi/4)
    &rArr; 0.70711
</pre></div>

<a name="XREFis_005ffunction_005fhandle"></a><dl>
<dt><a name="index-is_005ffunction_005fhandle"></a>: <em></em> <strong>is_function_handle</strong> <em>(<var>x</var>)</em></dt>
<dd><p>Return true if <var>x</var> is a function handle.
</p>
<p><strong>See also:</strong> <a href="Built_002din-Data-Types.html#XREFisa">isa</a>, <a href="Data-Types.html#XREFtypeinfo">typeinfo</a>, <a href="Built_002din-Data-Types.html#XREFclass">class</a>, <a href="#XREFfunctions">functions</a>.
</p></dd></dl>


<a name="XREFfunctions"></a><dl>
<dt><a name="index-functions"></a>: <em><var>s</var> =</em> <strong>functions</strong> <em>(<var>fcn_handle</var>)</em></dt>
<dd><p>Return a structure containing information about the function handle
<var>fcn_handle</var>.
</p>
<p>The structure <var>s</var> always contains these three fields:
</p>
<dl compact="compact">
<dt>function</dt>
<dd><p>The function name.  For an anonymous function (no name) this will be the
actual function definition.
</p>
</dd>
<dt>type</dt>
<dd><p>Type of the function.
</p>
<dl compact="compact">
<dt>anonymous</dt>
<dd><p>The function is anonymous.
</p>
</dd>
<dt>private</dt>
<dd><p>The function is private.
</p>
</dd>
<dt>overloaded</dt>
<dd><p>The function overloads an existing function.
</p>
</dd>
<dt>simple</dt>
<dd><p>The function is a built-in or m-file function.
</p>
</dd>
<dt>subfunction</dt>
<dd><p>The function is a subfunction within an m-file.
</p></dd>
</dl>

</dd>
<dt>file</dt>
<dd><p>The m-file that will be called to perform the function.  This field is empty
for anonymous and built-in functions.
</p></dd>
</dl>

<p>In addition, some function types may return more information in additional
fields.
</p>
<p><strong>Warning:</strong> <code>functions</code> is provided for debugging purposes only.
Its behavior may change in the future and programs should not depend on any
particular output format.
</p>

<p><strong>See also:</strong> <a href="#XREFfunc2str">func2str</a>, <a href="#XREFstr2func">str2func</a>.
</p></dd></dl>


<a name="XREFfunc2str"></a><dl>
<dt><a name="index-func2str"></a>: <em></em> <strong>func2str</strong> <em>(<var>fcn_handle</var>)</em></dt>
<dd><p>Return a string containing the name of the function referenced by the
function handle <var>fcn_handle</var>.
</p>
<p><strong>See also:</strong> <a href="#XREFstr2func">str2func</a>, <a href="#XREFfunctions">functions</a>.
</p></dd></dl>


<a name="XREFstr2func"></a><dl>
<dt><a name="index-str2func"></a>: <em></em> <strong>str2func</strong> <em>(<var>fcn_name</var>)</em></dt>
<dt><a name="index-str2func-1"></a>: <em></em> <strong>str2func</strong> <em>(<var>fcn_name</var>, &quot;global&quot;)</em></dt>
<dd><p>Return a function handle constructed from the string <var>fcn_name</var>.
</p>
<p>If the optional <code>&quot;global&quot;</code> argument is passed, locally visible
functions are ignored in the lookup.
</p>
<p><strong>See also:</strong> <a href="#XREFfunc2str">func2str</a>, <a href="Inline-Functions.html#XREFinline">inline</a>, <a href="#XREFfunctions">functions</a>.
</p></dd></dl>


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<div class="header">
<p>
Next: <a href="Anonymous-Functions.html#Anonymous-Functions" accesskey="n" rel="next">Anonymous Functions</a>, Up: <a href="Function-Handles-Anonymous-Functions-Inline-Functions.html#Function-Handles-Anonymous-Functions-Inline-Functions" accesskey="u" rel="up">Function Handles Anonymous Functions Inline Functions</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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