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<?xml version="1.0" encoding="UTF-8"?>
<!--
* Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
* Copyright (C) INRIA -
*
* This file must be used under the terms of the CeCILL.
* This source file is licensed as described in the file COPYING, which
* you should have received as part of this distribution. The terms
* are also available at
* http://www.cecill.info/licences/Licence_CeCILL_V2.1-en.txt
*
-->
<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:svg="http://www.w3.org/2000/svg" xmlns:ns5="http://www.w3.org/1999/xhtml" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:db="http://docbook.org/ns/docbook" xml:id="length" xml:lang="en">
<refnamediv>
<refname>length</refname>
<refpurpose>length of object</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Calling Sequence</title>
<synopsis>n = length(M)</synopsis>
</refsynopsisdiv>
<refsection>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term>M</term>
<listitem>
<para>
a matrix (usual or polynomial or character string) or a
list.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>n</term>
<listitem>
<para>an integer or a matrix of integers.</para>
</listitem>
</varlistentry>
</variablelist>
</refsection>
<refsection>
<title>Description</title>
<para>
For usual or polynomial matrix <varname>n</varname> is the integer
equal to number of rows times number of columns
of <varname>M</varname>. (Also valid for <varname>M</varname>
a boolean matrix).
</para>
<para>
For matrices made of character strings (and in particular for a
character string) <function>length</function> returns in
<varname>n</varname> the length of entries of the matrix of
character strings <varname>M</varname>.
</para>
<para>
The length of a list is the number of elements in the list (also
given by <function>size</function>).
</para>
<para>
The length of a mlist is by default the number of elements in the
mlist, but you can overload it (see example). Note that for a non-string
hypermatrix, there is no need to overload the function. Indeed, <function>length</function>
returns the product of the dimensions of the hypermatrix.
</para>
<para>
<code>length('123')</code> is <literal>3</literal>.
<code>length([1,2;3,4])</code> is <literal>4</literal>.
</para>
<para>
<warning>
WARNING : <function>length</function> of a sparse matrix
returns the max of dimensions and not the product
of the dimensions. (For example:
<code>length(sparse(eye(12,2)))</code>
returns <code>max(12,2)</code> and not <literal>24</literal>).
Please use <literal>size(...,'*')</literal> with sparse matrix.
</warning>
</para>
</refsection>
<refsection>
<title>Examples</title>
<programlisting role="example"><![CDATA[
length([123 ; 456 ])
length(['hello world',SCI])
length(rand(2,2,2))
]]></programlisting>
<programlisting role="example"><![CDATA[
a = mlist(["myMlistT" "field1" "field2"],"aexample","bexampleb");
length(a)
// returns 3 default behaviour if length not overloaded for mlist
// we create an overload function for mlist of type myMlistT
function r = %myMlistT_length(M)
r = length(M.field1)
endfunction
length(a)
// returns 8 result of length(a.field1)
]]></programlisting>
</refsection>
<refsection role="see also">
<title>See Also</title>
<simplelist type="inline">
<member>
<link linkend="size">size</link>
</member>
</simplelist>
</refsection>
<refsection>
<title>History</title>
<revhistory>
<revision>
<revnumber>5.4.0</revnumber>
<revremark>
This function allows overloading for mlist type.
</revremark>
</revision>
</revhistory>
</refsection>
</refentry>
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