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<hr>
<h3 class="section" id="Variable_002dlength-Argument-Lists-1"><span>11.6 Variable-length Argument Lists<a class="copiable-link" href="#Variable_002dlength-Argument-Lists-1"> ¶</a></span></h3>
<a class="index-entry-id" id="index-variable_002dlength-argument-lists"></a>
<a class="index-entry-id" id="index-varargin"></a>
<a class="anchor" id="XREFvarargin"></a>
<p>Sometimes the number of input arguments is not known when the function
is defined. As an example think of a function that returns the smallest
of all its input arguments. For example:
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">a = smallest (1, 2, 3);
b = smallest (1, 2, 3, 4);
</pre></div></div>
<p>In this example both <code class="code">a</code> and <code class="code">b</code> would be 1. One way to write
the <code class="code">smallest</code> function is
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">function val = smallest (arg1, arg2, arg3, arg4, arg5)
<var class="var">body</var>
endfunction
</pre></div></div>
<p>and then use the value of <code class="code">nargin</code> to determine which of the input
arguments should be considered. The problem with this approach is
that it can only handle a limited number of input arguments.
</p>
<p>If the special parameter name <code class="code">varargin</code> appears at the end of a
function parameter list it indicates that the function takes a variable
number of input arguments. Using <code class="code">varargin</code> the function
looks like this
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">function val = smallest (varargin)
<var class="var">body</var>
endfunction
</pre></div></div>
<p>In the function body the input arguments can be accessed through the
variable <code class="code">varargin</code>. This variable is a cell array containing
all the input arguments. See <a class="xref" href="Cell-Arrays.html">Cell Arrays</a>, for details on working
with cell arrays. The <code class="code">smallest</code> function can now be defined
like this
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">function val = smallest (varargin)
val = min ([varargin{:}]);
endfunction
</pre></div></div>
<p>This implementation handles any number of input arguments, but it’s also
a very simple solution to the problem.
</p>
<p>A slightly more complex example of <code class="code">varargin</code> is a function
<code class="code">print_arguments</code> that prints all input arguments. Such a function
can be defined like this
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">function print_arguments (varargin)
for i = 1:length (varargin)
printf ("Input argument %d: ", i);
disp (varargin{i});
endfor
endfunction
</pre></div></div>
<p>This function produces output like this
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">print_arguments (1, "two", 3);
-| Input argument 1: 1
-| Input argument 2: two
-| Input argument 3: 3
</pre></div></div>
<a class="anchor" id="XREFparseparams"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-parseparams"><span><code class="def-type">[<var class="var">reg</var>, <var class="var">prop</var>] =</code> <strong class="def-name">parseparams</strong> <code class="def-code-arguments">(<var class="var">params</var>)</code><a class="copiable-link" href="#index-parseparams"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-parseparams-1"><span><code class="def-type">[<var class="var">reg</var>, <var class="var">var1</var>, …] =</code> <strong class="def-name">parseparams</strong> <code class="def-code-arguments">(<var class="var">params</var>, <var class="var">name1</var>, <var class="var">default1</var>, …)</code><a class="copiable-link" href="#index-parseparams-1"> ¶</a></span></dt>
<dd><p>Return in <var class="var">reg</var> the cell elements of <var class="var">param</var> up to the first
string element and in <var class="var">prop</var> all remaining elements beginning with the
first string element.
</p>
<p>For example:
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">[reg, prop] = parseparams ({1, 2, "linewidth", 10})
reg =
{
[1,1] = 1
[1,2] = 2
}
prop =
{
[1,1] = linewidth
[1,2] = 10
}
</pre></div></div>
<p>The parseparams function may be used to separate regular numeric arguments
from additional arguments given as property/value pairs of the
<var class="var">varargin</var> cell array.
</p>
<p>In the second form of the call, available options are specified directly
with their default values given as name-value pairs. If <var class="var">params</var> do
not form name-value pairs, or if an option occurs that does not match any
of the available options, an error occurs.
</p>
<p>When called from an m-file function, the error is prefixed with the name
of the caller function.
</p>
<p>The matching of options is case-insensitive.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFvarargin">varargin</a>, <a class="ref" href="Parsing-Arguments.html#XREFinputParser">inputParser</a>.
</p></dd></dl>
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