boost/libs/preprocessor/doc/ref/list_filter_d.html

   1 <html>
   2 <head>
   3         <title>BOOST_PP_LIST_FILTER_D</title>
   4         <link rel="stylesheet" type="text/css" href="../styles.css">
   5 </head>
   6 <body>
   7         <div style="margin-left:  0px;">
   8                 The <b>BOOST_PP_LIST_FILTER_D</b> macro filters a <i>list</i> according to a supplied criterion.&nbsp;
   9                 It reenters <b>BOOST_PP_WHILE</b> with maximum efficiency.
  10         </div>
  11         <h4>Usage</h4>
  12                 <div class="code">
  13                         <b>BOOST_PP_LIST_FILTER_D</b>(<i>d</i>, <i>pred</i>, <i>data</i>, <i>list</i>)
  14                 </div>
  15         <h4>Arguments</h4>
  16                 <dl>
  17                         <dt>d</dt>
  18                         <dd>
  19                                 The next available <b>BOOST_PP_WHILE</b> iteration.
  20                         </dd>
  21                         <dt>pred</dt>
  22                         <dd>
  23                                 A ternary predicate of the form <i>pred</i>(<i>d</i>, <i>data</i>, <i>elem</i>).&nbsp;
  24                                 This predicate is expanded by <b>BOOST_PP_LIST_FILTER</b> for each element in <i>list</i> with the next available <b>BOOST_PP_WHILE</b> iteration,
  25                                 the auxiliary <i>data</i>, and the current element in <i>list</i>.&nbsp;
  26                                 This macro must return a integral value in the range of <i>0</i> to <b>BOOST_PP_LIMIT_MAG</b>.&nbsp;
  27                                 If this predicate expands to non-zero for a certain element, that element is included in the resulting <i>list</i>.
  28                         </dd>
  29                         <dt>data</dt>
  30                         <dd>
  31                                 Auxiliary data passed to <i>pred</i>.
  32                         </dd>
  33                         <dt>list</dt>
  34                         <dd>
  35                                 The <i>list</i> to be filtered.
  36                         </dd>
  37                 </dl>
  38         <h4>Remarks</h4>
  39                 <div>
  40                         This macro expands <i>pred</i> for each element in <i>list</i>.&nbsp;
  41                         It builds a new <i>list</i> out of each element for which <i>pred</i> returns non-zero.
  42                 </div>
  43         <h4>See Also</h4>
  44                 <ul>
  45                         <li><a href="limit_mag.html">BOOST_PP_LIMIT_MAG</a></li>
  46                         <li><a href="list_filter.html">BOOST_PP_LIST_FILTER</a></li>
  47                 </ul>
  48         <h4>Requirements</h4>
  49                 <div>
  50                         <b>Header:</b> &nbsp;<a href="../headers/list/filter.html">&lt;boost/preprocessor/list/filter.hpp&gt;</a>
  51                 </div>
  52         <h4>Sample Code</h4>
  53 <div><pre>
  54 #include &lt;<a href="../headers/comparison/less_equal.html">boost/preprocessor/comparison/less_equal.hpp</a>&gt;
  55 #include &lt;<a href="../headers/list/filter.html">boost/preprocessor/list/filter.hpp</a>&gt;
  56 #include &lt;<a href="../headers/list/fold_right.html">boost/preprocessor/list/fold_right.hpp</a>&gt;
  57
  58 #define A (1, (2, (3, (4, <a href="nil.html">BOOST_PP_NIL</a>))))
  59 #define B (A, (A, (A, (A, <a href="nil.html">BOOST_PP_NIL</a>))))
  60
  61 #define PRED(d, data, x) <a href="less_equal.html">BOOST_PP_LESS_EQUAL</a>(x, data)
  62 #define OP(d, state, x) (<a href="list_filter_d.html">BOOST_PP_LIST_FILTER_D</a>(d, PRED, 2, x), state)
  63
  64 <a href="list_fold_right.html">BOOST_PP_LIST_FOLD_RIGHT</a>(OP, <a href="nil.html">BOOST_PP_NIL</a>, B)
  65 /*
  66    expands to:
  67    ((1, (2, <a href="nil.html">BOOST_PP_NIL</a>)),
  68    ((1, (2, <a href="nil.html">BOOST_PP_NIL</a>)),
  69    ((1, (2, <a href="nil.html">BOOST_PP_NIL</a>)),
  70    ((1, (2, <a href="nil.html">BOOST_PP_NIL</a>)),
  71       <a href="nil.html">BOOST_PP_NIL</a>))))
  72 */
  73 </pre></div>
  74         <hr size="1">
  75         <div style="margin-left: 0px;">
  76                 <i>© Copyright <a href="http://www.housemarque.com" target="_top">Housemarque Oy</a> 2002</i>
  77                 </br><i>© Copyright Paul Mensonides 2002</i>
  78         </div>
  79         <div style="margin-left: 0px;">
  80                 <p><small>Distributed under the Boost Software License, Version 1.0. (See
  81                 accompanying file <a href="../../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or
  82                 copy at <a href=
  83                 "http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a>)</small></p>
  84         </div>
  85 </body>
  86 </html>