1<?xml version="1.0" encoding="utf-8" ?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> 4<head> 5<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 6<meta name="generator" content="Docutils 0.7: http://docutils.sourceforge.net/" /> 7<title>The MPL Reference Manual: find_if</title> 8<link rel="stylesheet" href="../style.css" type="text/css" /> 9</head> 10<body class="docframe refmanual"> 11<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> 12<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> 13</tr></table><div class="header-separator"></div> 14<div class="section" id="find-if"> 15<h1><a class="toc-backref" href="./querying-algorithms.html#id1476">find_if</a></h1> 16<div class="section" id="id543"> 17<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> 18<pre class="literal-block"> 19template< 20 typename Sequence 21 , typename Pred 22 > 23struct <a href="./find-if.html" class="identifier">find_if</a> 24{ 25 typedef <em>unspecified</em> type; 26}; 27</pre> 28</div> 29<div class="section" id="id544"> 30<h3><a class="subsection-title" href="#description" name="description">Description</a></h3> 31<p>Returns an iterator to the first element in <tt class="literal"><span class="pre">Sequence</span></tt> that satisfies 32the predicate <tt class="literal"><span class="pre">Pred</span></tt>.</p> 33</div> 34<div class="section" id="id545"> 35<h3><a class="subsection-title" href="#header" name="header">Header</a></h3> 36<pre class="literal-block"> 37#include <<a href="../../../../boost/mpl/find_if.hpp" class="header">boost/mpl/find_if.hpp</a>> 38</pre> 39</div> 40<div class="section" id="id546"> 41<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> 42<table border="1" class="docutils table"> 43<colgroup> 44<col width="19%" /> 45<col width="38%" /> 46<col width="43%" /> 47</colgroup> 48<thead valign="bottom"> 49<tr><th class="head">Parameter</th> 50<th class="head">Requirement</th> 51<th class="head">Description</th> 52</tr> 53</thead> 54<tbody valign="top"> 55<tr><td><tt class="literal"><span class="pre">Sequence</span></tt></td> 56<td><a class="reference internal" href="./forward-sequence.html">Forward Sequence</a></td> 57<td>A sequence to search in.</td> 58</tr> 59<tr><td><tt class="literal"><span class="pre">Pred</span></tt></td> 60<td>Unary <a class="reference internal" href="./lambda-expression.html">Lambda Expression</a></td> 61<td>A search condition.</td> 62</tr> 63</tbody> 64</table> 65</div> 66<div class="section" id="id547"> 67<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> 68<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> 69<pre class="literal-block"> 70typedef <a href="./find-if.html" class="identifier">find_if</a><s,pred>::type i; 71</pre> 72<table class="docutils field-list" frame="void" rules="none"> 73<col class="field-name" /> 74<col class="field-body" /> 75<tbody valign="top"> 76<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> 77</td> 78</tr> 79<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> 80<pre class="literal-block"> 81<a href="./apply.html" class="identifier">apply</a>< pred,<a href="./deref.html" class="identifier">deref</a><i>::type >::type::value == true 82</pre> 83<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> 84</td> 85</tr> 86</tbody> 87</table> 88</div> 89<div class="section" id="id548"> 90<h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3> 91<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> 92</div> 93<div class="section" id="id549"> 94<h3><a class="subsection-title" href="#example" name="example">Example</a></h3> 95<pre class="literal-block"> 96typedef <a href="./vector.html" class="identifier">vector</a><char,int,unsigned,long,unsigned long> types; 97typedef <a href="./find-if.html" class="identifier">find_if</a><types, is_same<<a href="./placeholders.html" class="identifier">_1</a>,unsigned> >::type iter; 98 99<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same< <a href="./deref.html" class="identifier">deref</a><iter>::type, unsigned > )); 100<a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( iter::pos::value, ==, 2 ); 101</pre> 102</div> 103<div class="section" id="id550"> 104<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> 105<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> 106<!-- Algorithms/Querying Algorithms//contains |30 --> 107</div> 108</div> 109 110<div class="footer-separator"></div> 111<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> 112<td><div class="copyright-footer"><div class="copyright">Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams</div> 113Distributed under the Boost Software License, Version 1.0. (See accompanying 114file LICENSE_1_0.txt or copy at <a class="reference external" href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)</div></td></tr></table></body> 115</html> 116