<?xml version="1.0" encoding="utf-8" ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <meta name="generator" content="Docutils 0.7: http://docutils.sourceforge.net/" /> <title>The MPL Reference Manual: find_if</title> <link rel="stylesheet" href="../style.css" type="text/css" /> </head> <body class="docframe refmanual"> <table class="header"><tr class="header"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./find.html" class="navigation-link">Prev</a> <a href="./contains.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./find.html" class="navigation-link">Back</a> <a href="./contains.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./querying-algorithms.html" class="navigation-link">Up</a> <a href="../refmanual.html" class="navigation-link">Home</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./refmanual_toc.html" class="navigation-link">Full TOC</a></span></td> <td class="header-group page-location"><a href="../refmanual.html" class="navigation-link">Front Page</a> / <a href="./algorithms.html" class="navigation-link">Algorithms</a> / <a href="./querying-algorithms.html" class="navigation-link">Querying Algorithms</a> / <a href="./find-if.html" class="navigation-link">find_if</a></td> </tr></table><div class="header-separator"></div> <div class="section" id="find-if"> <h1><a class="toc-backref" href="./querying-algorithms.html#id1476">find_if</a></h1> <div class="section" id="id543"> <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> <pre class="literal-block"> template< typename Sequence , typename Pred > struct <a href="./find-if.html" class="identifier">find_if</a> { typedef <em>unspecified</em> type; }; </pre> </div> <div class="section" id="id544"> <h3><a class="subsection-title" href="#description" name="description">Description</a></h3> <p>Returns an iterator to the first element in <tt class="literal"><span class="pre">Sequence</span></tt> that satisfies the predicate <tt class="literal"><span class="pre">Pred</span></tt>.</p> </div> <div class="section" id="id545"> <h3><a class="subsection-title" href="#header" name="header">Header</a></h3> <pre class="literal-block"> #include <<a href="../../../../boost/mpl/find_if.hpp" class="header">boost/mpl/find_if.hpp</a>> </pre> </div> <div class="section" id="id546"> <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> <table border="1" class="docutils table"> <colgroup> <col width="19%" /> <col width="38%" /> <col width="43%" /> </colgroup> <thead valign="bottom"> <tr><th class="head">Parameter</th> <th class="head">Requirement</th> <th class="head">Description</th> </tr> </thead> <tbody valign="top"> <tr><td><tt class="literal"><span class="pre">Sequence</span></tt></td> <td><a class="reference internal" href="./forward-sequence.html">Forward Sequence</a></td> <td>A sequence to search in.</td> </tr> <tr><td><tt class="literal"><span class="pre">Pred</span></tt></td> <td>Unary <a class="reference internal" href="./lambda-expression.html">Lambda Expression</a></td> <td>A search condition.</td> </tr> </tbody> </table> </div> <div class="section" id="id547"> <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> <p>For any <a class="reference internal" href="./forward-sequence.html">Forward Sequence</a> <tt class="literal"><span class="pre">s</span></tt> and unary <a class="reference internal" href="./lambda-expression.html">Lambda Expression</a> <tt class="literal"><span class="pre">pred</span></tt>:</p> <pre class="literal-block"> typedef <a href="./find-if.html" class="identifier">find_if</a><s,pred>::type i; </pre> <table class="docutils field-list" frame="void" rules="none"> <col class="field-name" /> <col class="field-body" /> <tbody valign="top"> <tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first"><a class="reference internal" href="./forward-iterator.html">Forward Iterator</a>.</p> </td> </tr> <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first"><tt class="literal"><span class="pre">i</span></tt> is the first iterator in the range [<tt class="literal"><span class="pre"><a href="./begin.html" class="identifier">begin</a><s>::type</span></tt>, <tt class="literal"><span class="pre"><a href="./end.html" class="identifier">end</a><s>::type</span></tt>) such that</p> <pre class="literal-block"> <a href="./apply.html" class="identifier">apply</a>< pred,<a href="./deref.html" class="identifier">deref</a><i>::type >::type::value == true </pre> <p class="last">If no such iterator exists, <tt class="literal"><span class="pre">i</span></tt> is identical to <tt class="literal"><span class="pre"><a href="./end.html" class="identifier">end</a><s>::type</span></tt>.</p> </td> </tr> </tbody> </table> </div> <div class="section" id="id548"> <h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3> <p>Linear. At most <tt class="literal"><span class="pre"><a href="./size.html" class="identifier">size</a><s>::value</span></tt> applications of <tt class="literal"><span class="pre">pred</span></tt>.</p> </div> <div class="section" id="id549"> <h3><a class="subsection-title" href="#example" name="example">Example</a></h3> <pre class="literal-block"> typedef <a href="./vector.html" class="identifier">vector</a><char,int,unsigned,long,unsigned long> types; typedef <a href="./find-if.html" class="identifier">find_if</a><types, is_same<<a href="./placeholders.html" class="identifier">_1</a>,unsigned> >::type iter; <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same< <a href="./deref.html" class="identifier">deref</a><iter>::type, unsigned > )); <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( iter::pos::value, ==, 2 ); </pre> </div> <div class="section" id="id550"> <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> <p><a class="reference internal" href="./querying-algorithms.html">Querying Algorithms</a>, <a class="reference internal" href="./find.html">find</a>, <a class="reference internal" href="./count-if.html">count_if</a>, <a class="reference internal" href="./lower-bound.html">lower_bound</a></p> <!-- Algorithms/Querying Algorithms//contains |30 --> </div> </div> <div class="footer-separator"></div> <table class="footer"><tr class="footer"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./find.html" class="navigation-link">Prev</a> <a href="./contains.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./find.html" class="navigation-link">Back</a> <a href="./contains.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./querying-algorithms.html" class="navigation-link">Up</a> <a href="../refmanual.html" class="navigation-link">Home</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./refmanual_toc.html" class="navigation-link">Full TOC</a></span></td> <td><div class="copyright-footer"><div class="copyright">Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams</div> Distributed under the Boost Software License, Version 1.0. 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