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<div class="subsection" id="Function-Handles">
<div class="header">
<p>
Next: <a href="Anonymous-Functions.html" accesskey="n" rel="next">Anonymous Functions</a>, Up: <a href="Function-Handles-and-Anonymous-Functions.html" accesskey="u" rel="up">Function Handles and Anonymous Functions</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<span id="Function-Handles-1"></span><h4 class="subsection">11.12.1 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)
⇒ 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
‘<samp>()</samp>’. For example:
</p>
<div class="example">
<pre class="example">f = @sin;
feval (f, pi/4)
⇒ 0.70711
f (pi/4)
⇒ 0.70711
</pre></div>
<span id="XREFis_005ffunction_005fhandle"></span><dl class="def">
<dt id="index-is_005ffunction_005fhandle"><span class="category">: </span><span><em></em> <strong>is_function_handle</strong> <em>(<var>x</var>)</em><a href='#index-is_005ffunction_005fhandle' class='copiable-anchor'> ¶</a></span></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>
<span id="XREFfunctions"></span><dl class="def">
<dt id="index-functions"><span class="category">: </span><span><em><var>s</var> =</em> <strong>functions</strong> <em>(<var>fcn_handle</var>)</em><a href='#index-functions' class='copiable-anchor'> ¶</a></span></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><span>function</span></dt>
<dd><p>The function name. For an anonymous function (no name) this will be the
actual function definition.
</p>
</dd>
<dt><span>type</span></dt>
<dd><p>Type of the function.
</p>
<dl compact="compact">
<dt><span>anonymous</span></dt>
<dd><p>The function is anonymous.
</p>
</dd>
<dt><span>private</span></dt>
<dd><p>The function is private.
</p>
</dd>
<dt><span>overloaded</span></dt>
<dd><p>The function overloads an existing function.
</p>
</dd>
<dt><span>simple</span></dt>
<dd><p>The function is a built-in or m-file function.
</p>
</dd>
<dt><span>subfunction</span></dt>
<dd><p>The function is a subfunction within an m-file.
</p></dd>
</dl>
</dd>
<dt><span>nested</span></dt>
<dd><p>The function is nested.
</p>
</dd>
<dt><span>file</span></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>
<span id="XREFfunc2str"></span><dl class="def">
<dt id="index-func2str"><span class="category">: </span><span><em></em> <strong>func2str</strong> <em>(<var>fcn_handle</var>)</em><a href='#index-func2str' class='copiable-anchor'> ¶</a></span></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>
<span id="XREFstr2func"></span><dl class="def">
<dt id="index-str2func"><span class="category">: </span><span><em></em> <strong>str2func</strong> <em>(<var>fcn_name</var>)</em><a href='#index-str2func' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>Return a function handle constructed from the string <var>fcn_name</var>.
</p>
<p>Previous versions of Octave accepted an optional second argument,
<code>"global"</code>, that caused str2func to ignore locally visible
functions. This option is no longer supported.
</p>
<p><strong>See also:</strong> <a href="#XREFfunc2str">func2str</a>, <a href="#XREFfunctions">functions</a>.
</p></dd></dl>
<span id="XREFsymvar"></span><dl class="def">
<dt id="index-symvar"><span class="category">: </span><span><em><var>vars</var> =</em> <strong>symvar</strong> <em>(<var>str</var>)</em><a href='#index-symvar' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>Identify the symbolic variable names in the string <var>str</var>.
</p>
<p>Common constant names such as <code>i</code>, <code>j</code>, <code>pi</code>, <code>Inf</code> and
Octave functions such as <code>sin</code> or <code>plot</code> are ignored.
</p>
<p>Any names identified are returned in a cell array of strings. The array is
empty if no variables were found.
</p>
<p>Example:
</p>
<div class="example">
<pre class="example">symvar ("x^2 + y^2 == 4")
⇒ {
[1,1] = x
[2,1] = y
}
</pre></div>
</dd></dl>
</div>
<hr>
<div class="header">
<p>
Next: <a href="Anonymous-Functions.html">Anonymous Functions</a>, Up: <a href="Function-Handles-and-Anonymous-Functions.html">Function Handles and Anonymous Functions</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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