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<h3 class="section">11.4 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.
<pre class="example"> function val = pick2nd (~, arg2)
val = arg2;
endfunction
</pre>
<p>The value of <code>nargin</code> is not affected by using this declaration.
<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:
<pre class="example"> function [out1, out2] = long_function (x, y, z)
if (isargout (1))
## Long calculation
...
out1 = result;
endif
...
endfunction
</pre>
<!-- isargout src/ov-usr-fcn.cc -->
<p><a name="doc_002disargout"></a>
<div class="defun">
— Built-in Function: <b>isargout</b> (<var>k</var>)<var><a name="index-isargout-746"></a></var><br>
<blockquote><p>Within a function, return a logical value indicating whether the argument
<var>k</var> will be assigned on output to a variable. 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>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.
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dnargout.html#doc_002dnargout">nargout</a>, <a href="doc_002dnargin.html#doc_002dnargin">nargin</a>, <a href="doc_002dvarargin.html#doc_002dvarargin">varargin</a>, <a href="doc_002dvarargout.html#doc_002dvarargout">varargout</a>, <a href="doc_002dnthargout.html#doc_002dnthargout">nthargout</a>.
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