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<?xml version="1.0" encoding="UTF-8"?>
<!--
* Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
* Copyright (C) ????-2008 - 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-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:mml="http://www.w3.org/1998/Math/MathML"
xmlns:db="http://docbook.org/ns/docbook"
version="5.0-subset Scilab"
xml:lang="en" xml:id="functions">
<info>
<pubdate>$LastChangedDate$</pubdate>
</info>
<refnamediv>
<refname>functions</refname>
<refpurpose> Scilab procedures and Scilab objects</refpurpose>
</refnamediv>
<refsection>
<title>Description</title>
<para>Functions are Scilab procedures ("macro", "function" and "procedure"
have the save meaning).</para>
</refsection>
<refsection>
<title>Function definition</title>
<para>Usually, they are defined in files with an editor and loaded into
Scilab using the <link linkend="exec">exec</link> function or through a library (see
<link linkend="lib">lib</link> or <link linkend="genlib">genlib</link>). But They can also be
defined on-line (see <link linkend="deff">deff</link> or <link linkend="function">function</link>.
A function is defined by two components: </para>
<itemizedlist>
<listitem>
<para>a "syntax definition" part as follows:</para>
<programlisting><![CDATA[
function [y1,...,yn]=foo(x1,...,xm)
function [y1,...,yn,varargout]=foo(x1,...,xm,varargin)
]]></programlisting>
</listitem>
<listitem>
<para>a sequence of scilab instructions.</para>
</listitem>
</itemizedlist>
<para>The "syntax definition" line gives the "full" calling syntax of
this function. The <literal>yi</literal> are output variables
calculated as functions of input variables <literal>xi</literal>
and variables existing in Scilab when the function is
executed.</para>
</refsection>
<refsection>
<title>Calling function</title>
<itemizedlist>
<listitem>
<para>Usually function calling syntax is
<literal>[y1,...,yn]=foo(x1,...,xm)</literal>. Shorter input or
output argument list than definition ones may be used. In such
cases, only the first variables from the left are used or set.</para>
<para>The <link linkend="argn">argn</link> function may be used to get
the actual number of calling arguments.</para>
</listitem>
<listitem>
<para>It is possible to define function with indeterminate
number of input or output maximum number of arguments. This
can be done using the <link linkend="varargin">varargin</link>
and <link linkend="varargout">varargout</link>
keywords. See the given links for details.</para>
</listitem>
<listitem>
<para>It is also possible to use "named argument" to specify input
arguments: suppose function <literal>fun1</literal> defined as
<literal>function y1=fun1(x1,x2,x3)</literal> then it can be
called with a syntax like <literal>y=fun1(x1=33,x3=[1 2
3])</literal> within <literal>fun1</literal> x2 will be
undefined,</para>
<para> it can also be called with a syntax like
<literal>y=fun1(x1=33,y='foo')</literal>. In such a case the
<literal>y</literal> variable will be available in the context
of the function <literal>fun1</literal>. Note that the maximum
number of argument must be less or equal to the number of
formal input argument used in the function syntax part.</para>
<para> It is possible to check for defined variables with the
<link linkend="exists">exists</link> function.</para>
</listitem>
<listitem>
<para>When a function has no left hand side argument and is called only
with character string arguments, the calling syntax may be
simplified:</para>
<programlisting><![CDATA[
fun('a','toto','a string')
]]></programlisting>
<para>is equivalent to: </para>
<programlisting><![CDATA[
fun a toto 'a string'
]]></programlisting>
</listitem>
</itemizedlist>
</refsection>
<refsection>
<title>Miscellaneous</title>
<para>
Functions are Scilab objects (with type numbers 13 or 11). They
and can be manipulated (built, saved, loaded, passed as
arguments,..) as other variable types.</para>
<para>Collections of functions can be collected in libraries. Functions
which begin with <literal>%</literal> sign
(e.g. <literal>%foo</literal>) are often used to overload (see <link linkend="overloading">overloading</link>
) operations or functions for new data type.</para>
</refsection>
<refsection>
<title>Examples</title>
<programlisting role="example"><![CDATA[
//inline definition (see function)
function [x,y]=myfct(a,b)
x=a+b
y=a-b
endfunction
[x,y]=myfct(3,2)
//inline definition (see deff)
deff('[x,y]=myfct(a,b)',['x=a+b';
'y=a-b'])
// definition in an ascii file (see exec)
exec SCI/modules/elementary_functions/macros/asinh.sci;
]]></programlisting>
</refsection>
<refsection>
<title>See Also</title>
<simplelist type="inline">
<member> <link linkend="function">function</link> </member>
<member> <link linkend="deff">deff</link> </member>
<member> <link linkend="exec">exec</link> </member>
<member> <link linkend="comp">comp</link> </member>
<member> <link linkend="lib">lib</link> </member>
<member> <link linkend="getd">getd</link> </member>
<member> <link linkend="genlib">genlib</link> </member>
<member> <link linkend="exists">exists</link> </member>
<member> <link linkend="varargin">varargin</link> </member>
<member> <link linkend="varargout">varargout</link> </member>
</simplelist>
</refsection>
</refentry>
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