1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>filter_if</title> 5<link rel="stylesheet" href="../../../../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../../../index.html" title="Chapter 1. Fusion 2.2"> 8<link rel="up" href="../metafunctions.html" title="Metafunctions"> 9<link rel="prev" href="filter.html" title="filter"> 10<link rel="next" href="transform.html" title="transform"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="filter.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../metafunctions.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="transform.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h5 class="title"> 27<a name="fusion.algorithm.transformation.metafunctions.filter_if"></a><a class="link" href="filter_if.html" title="filter_if">filter_if</a> 28</h5></div></div></div> 29<h6> 30<a name="fusion.algorithm.transformation.metafunctions.filter_if.h0"></a> 31 <span class="phrase"><a name="fusion.algorithm.transformation.metafunctions.filter_if.description"></a></span><a class="link" href="filter_if.html#fusion.algorithm.transformation.metafunctions.filter_if.description">Description</a> 32 </h6> 33<p> 34 Returns the result type of <a class="link" href="../functions/filter_if.html" title="filter_if"><code class="computeroutput"><span class="identifier">filter_if</span></code></a> given the sequence 35 and unary <a href="http://www.boost.org/libs/mpl/doc/refmanual/lambda-expression.html" target="_top">MPL 36 Lambda Expression</a> predicate type. 37 </p> 38<h6> 39<a name="fusion.algorithm.transformation.metafunctions.filter_if.h1"></a> 40 <span class="phrase"><a name="fusion.algorithm.transformation.metafunctions.filter_if.synopsis"></a></span><a class="link" href="filter_if.html#fusion.algorithm.transformation.metafunctions.filter_if.synopsis">Synopsis</a> 41 </h6> 42<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> 43 <span class="keyword">typename</span> <span class="identifier">Sequence</span><span class="special">,</span> 44 <span class="keyword">typename</span> <span class="identifier">Pred</span> 45 <span class="special">></span> 46<span class="keyword">struct</span> <span class="identifier">filter_if</span> 47<span class="special">{</span> 48 <span class="keyword">typedef</span> <span class="emphasis"><em>unspecified</em></span> <span class="identifier">type</span><span class="special">;</span> 49<span class="special">};</span> 50</pre> 51<div class="table"> 52<a name="fusion.algorithm.transformation.metafunctions.filter_if.t0"></a><p class="title"><b>Table 1.88. Parameter</b></p> 53<div class="table-contents"><table class="table" summary="Parameter"> 54<colgroup> 55<col> 56<col> 57<col> 58</colgroup> 59<thead><tr> 60<th> 61 <p> 62 Parameter 63 </p> 64 </th> 65<th> 66 <p> 67 Requirement 68 </p> 69 </th> 70<th> 71 <p> 72 Description 73 </p> 74 </th> 75</tr></thead> 76<tbody> 77<tr> 78<td> 79 <p> 80 <code class="computeroutput"><span class="identifier">Sequence</span></code> 81 </p> 82 </td> 83<td> 84 <p> 85 A model of <a class="link" href="../../../sequence/concepts/forward_sequence.html" title="Forward Sequence">Forward 86 Sequence</a> 87 </p> 88 </td> 89<td> 90 <p> 91 Operation's argument 92 </p> 93 </td> 94</tr> 95<tr> 96<td> 97 <p> 98 <code class="computeroutput"><span class="identifier">Pred</span></code> 99 </p> 100 </td> 101<td> 102 <p> 103 A unary <a href="http://www.boost.org/libs/mpl/doc/refmanual/lambda-expression.html" target="_top">MPL 104 Lambda Expression</a> 105 </p> 106 </td> 107<td> 108 <p> 109 Type to retain 110 </p> 111 </td> 112</tr> 113</tbody> 114</table></div> 115</div> 116<br class="table-break"><h6> 117<a name="fusion.algorithm.transformation.metafunctions.filter_if.h2"></a> 118 <span class="phrase"><a name="fusion.algorithm.transformation.metafunctions.filter_if.expression_semantics"></a></span><a class="link" href="filter_if.html#fusion.algorithm.transformation.metafunctions.filter_if.expression_semantics">Expression 119 Semantics</a> 120 </h6> 121<pre class="programlisting"><a class="link" href="filter_if.html" title="filter_if"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">filter_if</span></code></a><span class="special"><</span><span class="identifier">Sequence</span><span class="special">,</span> <span class="identifier">Pred</span><span class="special">>::</span><span class="identifier">type</span> 122</pre> 123<p> 124 <span class="bold"><strong>Return type</strong></span>: 125 </p> 126<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 127<li class="listitem"> 128 A model of <a class="link" href="../../../sequence/concepts/forward_sequence.html" title="Forward Sequence">Forward 129 Sequence</a>. 130 </li> 131<li class="listitem"> 132 A model of <a class="link" href="../../../sequence/concepts/associative_sequence.html" title="Associative Sequence">Associative 133 Sequence</a> if <code class="computeroutput"><span class="identifier">Sequence</span></code> 134 implements the <a class="link" href="../../../sequence/concepts/associative_sequence.html" title="Associative Sequence">Associative 135 Sequence</a> model. 136 </li> 137</ul></div> 138<p> 139 <span class="bold"><strong>Semantics</strong></span>: Returns a sequence containing 140 the elements of <code class="computeroutput"><span class="identifier">Sequence</span></code> 141 for which <code class="computeroutput"><span class="identifier">Pred</span></code> evaluates 142 to <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span></code>. 143 </p> 144<h6> 145<a name="fusion.algorithm.transformation.metafunctions.filter_if.h3"></a> 146 <span class="phrase"><a name="fusion.algorithm.transformation.metafunctions.filter_if.complexity"></a></span><a class="link" href="filter_if.html#fusion.algorithm.transformation.metafunctions.filter_if.complexity">Complexity</a> 147 </h6> 148<p> 149 Constant. 150 </p> 151<h6> 152<a name="fusion.algorithm.transformation.metafunctions.filter_if.h4"></a> 153 <span class="phrase"><a name="fusion.algorithm.transformation.metafunctions.filter_if.header"></a></span><a class="link" href="filter_if.html#fusion.algorithm.transformation.metafunctions.filter_if.header">Header</a> 154 </h6> 155<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">algorithm</span><span class="special">/</span><span class="identifier">transformation</span><span class="special">/</span><span class="identifier">filter_if</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 156<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">filter_if</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 157</pre> 158</div> 159<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 160<td align="left"></td> 161<td align="right"><div class="copyright-footer">Copyright © 2001-2006, 2011, 2012 Joel de Guzman, 162 Dan Marsden, Tobias Schwinger<p> 163 Distributed under the Boost Software License, Version 1.0. (See accompanying 164 file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 165 </p> 166</div></td> 167</tr></table> 168<hr> 169<div class="spirit-nav"> 170<a accesskey="p" href="filter.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../metafunctions.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="transform.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 171</div> 172</body> 173</html> 174
