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<a name="Ignoring-Arguments"></a>
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<p>
Next: <a href="Variable_002dlength-Return-Lists.html#Variable_002dlength-Return-Lists" accesskey="n" rel="next">Variable-length Return Lists</a>, Previous: <a href="Variable_002dlength-Argument-Lists.html#Variable_002dlength-Argument-Lists" accesskey="p" rel="prev">Variable-length Argument Lists</a>, Up: <a href="Functions-and-Scripts.html#Functions-and-Scripts" accesskey="u" rel="up">Functions and Scripts</a> [<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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<a name="Ignoring-Arguments-1"></a>
<h3 class="section">11.5 Ignoring Arguments</h3>
<p>In the formal argument list, it is possible to use the dummy placeholder
<code>~</code> instead of a name. This indicates that the corresponding argument
value should be ignored and not stored to any variable.
</p>
<div class="example">
<pre class="example">function val = pick2nd (~, arg2)
val = arg2;
endfunction
</pre></div>
<p>The value of <code>nargin</code> is not affected by using this declaration.
</p>
<p>Return arguments can also be ignored using the same syntax. Functions may
take advantage of ignored outputs to reduce the number of calculations
performed. To do so, use the <code>isargout</code> function to query whether the
output argument is wanted. For example:
</p>
<div class="example">
<pre class="example">function [out1, out2] = long_function (x, y, z)
if (isargout (1))
## Long calculation
…
out1 = result;
endif
…
endfunction
</pre></div>
<a name="XREFisargout"></a><dl>
<dt><a name="index-isargout"></a>Built-in Function: <em></em> <strong>isargout</strong> <em>(<var>k</var>)</em></dt>
<dd><p>Within a function, return a logical value indicating whether the argument
<var>k</var> will be assigned to a variable on output. If the result is false,
the argument has been ignored during the function call through the use of
the tilde (~) special output argument. Functions can use <code>isargout</code> to
avoid performing unnecessary calculations for outputs which are unwanted.
</p>
<p>If <var>k</var> is outside the range <code>1:max (nargout)</code>, the function returns
false. <var>k</var> can also be an array, in which case the function works
element-by-element and a logical array is returned. At the top level,
<code>isargout</code> returns an error.
</p>
<p><strong>See also:</strong> <a href="Multiple-Return-Values.html#XREFnargout">nargout</a>, <a href="Defining-Functions.html#XREFnargin">nargin</a>, <a href="Multiple-Return-Values.html#XREFvarargin">varargin</a>, <a href="Multiple-Return-Values.html#XREFvarargout">varargout</a>, <a href="Multiple-Return-Values.html#XREFnthargout">nthargout</a>.
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