<?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: count_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="./count.html" class="navigation-link">Prev</a> <a href="./lower-bound.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./count.html" class="navigation-link">Back</a> <a href="./lower-bound.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="./count-if.html" class="navigation-link">count_if</a></td> </tr></table><div class="header-separator"></div> <div class="section" id="count-if"> <h1><a class="toc-backref" href="./querying-algorithms.html#id1479">count_if</a></h1> <div class="section" id="id567"> <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> <pre class="literal-block"> template< typename Sequence , typename Pred > struct <a href="./count-if.html" class="identifier">count_if</a> { typedef <em>unspecified</em> type; }; </pre> </div> <div class="section" id="id568"> <h3><a class="subsection-title" href="#description" name="description">Description</a></h3> <p>Returns the number of elements in <tt class="literal"><span class="pre">Sequence</span></tt> that satisfy the predicate <tt class="literal"><span class="pre">Pred</span></tt>.</p> </div> <div class="section" id="id569"> <h3><a class="subsection-title" href="#header" name="header">Header</a></h3> <pre class="literal-block"> #include <<a href="../../../../boost/mpl/count_if.hpp" class="header">boost/mpl/count_if.hpp</a>> </pre> </div> <div class="section" id="id570"> <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 be examined.</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 count condition.</td> </tr> </tbody> </table> </div> <div class="section" id="id571"> <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="./count-if.html" class="identifier">count_if</a><s,pred>::type n; </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="./integral-constant.html">Integral Constant</a>.</p> </td> </tr> <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p> <pre class="last literal-block"> typedef <a href="./lambda.html" class="identifier">lambda</a><pred>::type p; typedef <a href="./fold.html" class="identifier">fold</a>< s , <a href="./long.html" class="identifier">long_</a><0> , <a href="./if.html" class="identifier">if_</a>< <a href="./apply-wrap.html" class="identifier">apply_wrap</a><tt class="literal"><span class="pre">1</span></tt><p,<a href="./placeholders.html" class="identifier">_2</a>>, <a href="./next.html" class="identifier">next</a><<a href="./placeholders.html" class="identifier">_1</a>>, <a href="./placeholders.html" class="identifier">_1</a> > >::type n; </pre> </td> </tr> </tbody> </table> </div> <div class="section" id="id572"> <h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3> <p>Linear. Exactly <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="id573"> <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><int,char,long,short,char,long,double,long> types; <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( (<a href="./count-if.html" class="identifier">count_if</a>< types, is_float<_> >::value), ==, 1 ); <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( (<a href="./count-if.html" class="identifier">count_if</a>< types, is_same<_,char> >::value), ==, 2 ); <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( (<a href="./count-if.html" class="identifier">count_if</a>< types, is_same<_,void> >::value), ==, 0 ); </pre> </div> <div class="section" id="id574"> <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="./count.html">count</a>, <a class="reference internal" href="./find.html">find</a>, <a class="reference internal" href="./find-if.html">find_if</a>, <a class="reference internal" href="./contains.html">contains</a></p> <!-- Algorithms/Querying Algorithms//lower_bound |60 --> </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="./count.html" class="navigation-link">Prev</a> <a href="./lower-bound.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./count.html" class="navigation-link">Back</a> <a href="./lower-bound.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. (See accompanying file 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> </html>