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  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">&lt;</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">&gt;</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&#160;1.86.&#160;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">&lt;</span><span class="identifier">Sequence</span><span class="special">,</span> <span class="identifier">Pred</span><span class="special">&gt;::</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">&lt;</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">&gt;</span>
 156 <span class="preprocessor">#include</span> <span class="special">&lt;</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">&gt;</span>
 157 </pre>
 158 </div>
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 160 <td align="left"></td>
 161 <td align="right"><div class="copyright-footer">Copyright &#169; 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>)
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