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6 | <meta name="generator" content="Docutils 0.7: http://docutils.sourceforge.net/" /> | |
7 | <title>The MPL Reference Manual: count_if</title> | |
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10 | <body class="docframe refmanual"> | |
11 | <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> | |
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="./count-if.html" class="navigation-link">count_if</a></td> | |
13 | </tr></table><div class="header-separator"></div> | |
14 | <div class="section" id="count-if"> | |
15 | <h1><a class="toc-backref" href="./querying-algorithms.html#id1479">count_if</a></h1> | |
16 | <div class="section" id="id567"> | |
17 | <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> | |
18 | <pre class="literal-block"> | |
19 | template< | |
20 | typename Sequence | |
21 | , typename Pred | |
22 | > | |
23 | struct <a href="./count-if.html" class="identifier">count_if</a> | |
24 | { | |
25 | typedef <em>unspecified</em> type; | |
26 | }; | |
27 | </pre> | |
28 | </div> | |
29 | <div class="section" id="id568"> | |
30 | <h3><a class="subsection-title" href="#description" name="description">Description</a></h3> | |
31 | <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> | |
32 | </div> | |
33 | <div class="section" id="id569"> | |
34 | <h3><a class="subsection-title" href="#header" name="header">Header</a></h3> | |
35 | <pre class="literal-block"> | |
36 | #include <<a href="../../../../boost/mpl/count_if.hpp" class="header">boost/mpl/count_if.hpp</a>> | |
37 | </pre> | |
38 | </div> | |
39 | <div class="section" id="id570"> | |
40 | <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> | |
41 | <table border="1" class="docutils table"> | |
42 | <colgroup> | |
43 | <col width="19%" /> | |
44 | <col width="38%" /> | |
45 | <col width="43%" /> | |
46 | </colgroup> | |
47 | <thead valign="bottom"> | |
48 | <tr><th class="head">Parameter</th> | |
49 | <th class="head">Requirement</th> | |
50 | <th class="head">Description</th> | |
51 | </tr> | |
52 | </thead> | |
53 | <tbody valign="top"> | |
54 | <tr><td><tt class="literal"><span class="pre">Sequence</span></tt></td> | |
55 | <td><a class="reference internal" href="./forward-sequence.html">Forward Sequence</a></td> | |
56 | <td>A sequence to be examined.</td> | |
57 | </tr> | |
58 | <tr><td><tt class="literal"><span class="pre">Pred</span></tt></td> | |
59 | <td>Unary <a class="reference internal" href="./lambda-expression.html">Lambda Expression</a></td> | |
60 | <td>A count condition.</td> | |
61 | </tr> | |
62 | </tbody> | |
63 | </table> | |
64 | </div> | |
65 | <div class="section" id="id571"> | |
66 | <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> | |
67 | <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> | |
68 | <pre class="literal-block"> | |
69 | typedef <a href="./count-if.html" class="identifier">count_if</a><s,pred>::type n; | |
70 | </pre> | |
71 | <table class="docutils field-list" frame="void" rules="none"> | |
72 | <col class="field-name" /> | |
73 | <col class="field-body" /> | |
74 | <tbody valign="top"> | |
75 | <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> | |
76 | </td> | |
77 | </tr> | |
78 | <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p> | |
79 | <pre class="last literal-block"> | |
80 | typedef <a href="./lambda.html" class="identifier">lambda</a><pred>::type p; | |
81 | typedef <a href="./fold.html" class="identifier">fold</a>< | |
82 | s | |
83 | , <a href="./long.html" class="identifier">long_</a><0> | |
84 | , <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> > | |
85 | >::type n; | |
86 | </pre> | |
87 | </td> | |
88 | </tr> | |
89 | </tbody> | |
90 | </table> | |
91 | </div> | |
92 | <div class="section" id="id572"> | |
93 | <h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3> | |
94 | <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> | |
95 | </div> | |
96 | <div class="section" id="id573"> | |
97 | <h3><a class="subsection-title" href="#example" name="example">Example</a></h3> | |
98 | <pre class="literal-block"> | |
99 | typedef <a href="./vector.html" class="identifier">vector</a><int,char,long,short,char,long,double,long> types; | |
100 | ||
101 | <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 ); | |
102 | <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 ); | |
103 | <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 ); | |
104 | </pre> | |
105 | </div> | |
106 | <div class="section" id="id574"> | |
107 | <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> | |
108 | <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> | |
109 | <!-- Algorithms/Querying Algorithms//lower_bound |60 --> | |
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112 | ||
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115 | <td><div class="copyright-footer"><div class="copyright">Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams</div> | |
116 | Distributed under the Boost Software License, Version 1.0. (See accompanying | |
117 | 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> | |
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