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<?xml version="1.0" encoding="ISO-8859-1"?>
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<refentry id="xpf_if">
<refmeta>
<refentrytitle>if</refentrytitle>
<refmiscinfo>XPATH</refmiscinfo>
</refmeta>
<refnamediv>
<refname>if</refname>
<refpurpose>If the boolean value is true then calculates one expression, otherwise calculates another expression.</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis id="xpf_syn_if">
<funcprototype id="xpf_proto_if">
<funcdef>any <function>if</function></funcdef>
<paramdef><parameter>test</parameter> boolean</paramdef>
<paramdef><parameter>then_branch</parameter> any</paramdef>
<paramdef><parameter>else_branch</parameter> any</paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 id="xpf_desc_if"><title>Description</title>
<para>
This function calculates the value of <parameter>test</parameter> argument.
If the value is true, the function calculates the <parameter>then_branch</parameter>
expression and returns its value.
If the value is false, the function calculates the <parameter>else_branch</parameter>
expression and returns its value.
</para>
<para>
Note that unlike other programming languages, <parameter>else_branch</parameter>
is required argument, not optional.
</para>
<para>
This function is used in the implementation of
"IF" control operator in XQUERY,
so you will probably use that operator in XQUERY expressions, not the function.
This function may be useful in XPATH expressions and in XSLT stylesheets.
It is not a part of library of standard XQUERY 1.0 functions.
</para>
</refsect1>
<refsect1 id="xpf_params_if"><title>Parameters</title>
<refsect2><title>test</title>
<para>Boolean value used to choose an expression to execute</para></refsect2>
<refsect2><title>then_branch</title>
<para>Expression which is calculated if <parameter>test</parameter> argument is true</para></refsect2>
<refsect2><title>else_branch</title>
<para>Expression which is calculated if <parameter>test</parameter> argument is false</para></refsect2>
</refsect1>
<refsect1 id="xpf_ret_if"><title>Return Types</title><para>Any</para></refsect1>
<refsect1 id="xpf_examples_if"><title>Examples</title>
<example id="xpf_ex_if"><title></title>
<para>These two expressions are equivalent,
but first may be used in any XPATH while second is written in XQUERY syntax:</para>
<screen>
if (2 * 2 = 4, 'I think so', 'Unbelievable!')
IF 2 * 2 = 4 THEN 'I think so' ELSE 'Unbelievable!'
</screen>
</example>
</refsect1>
<refsect1 id="xpf_seealso_if"><title>See Also</title>
<para><link linkend="xpf_and">and()</link><link linkend="xpf_or">or()</link></para>
</refsect1>
</refentry>
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