projects / ceph.git / blame
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1 | <html> |
| 2 | <head> | |
| 3 | <title>BOOST_PP_SEQ_FILTER</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_SEQ_FILTER</b> macro filters a <i>seq</i> according to a | |
| 9 | supplied criterion. | |
| 10 | </div> | |
| 11 | <h4> | |
| 12 | Usage | |
| 13 | </h4> | |
| 14 | <div class="code"> | |
| 15 | <b>BOOST_PP_SEQ_FILTER</b>(<i>pred</i>, <i>data</i>, <i>seq</i>) | |
| 16 | </div> | |
| 17 | <h4> | |
| 18 | Arguments | |
| 19 | </h4> | |
| 20 | <dl> | |
| 21 | <dt>pred</dt> | |
| 22 | <dd> | |
| 23 | A ternary predicate of the form <i>pred</i>(<i>s</i>, <i>data</i>, <i>elem</i>). | |
| 24 | This predicate is expanded by <b>BOOST_PP_SEQ_FILTER</b> for each element in <i>seq</i> | |
| 25 | with the next available <b>BOOST_PP_SEQ_FOLD_LEFT</b> fold step, the auxiliary <i>data</i>, | |
| 26 | and the current element in <i>seq</i>. This macro must return a integral | |
| 27 | value in the range of <i>0</i> to <b>BOOST_PP_LIMIT_MAG</b>. If this | |
| 28 | predicate expands to non-zero for a certain element, that element is included | |
| 29 | in the resulting <i>seq</i>. | |
| 30 | </dd> | |
| 31 | <dt>data</dt> | |
| 32 | <dd> | |
| 33 | Auxiliary data passed to <i>pred</i>. | |
| 34 | </dd> | |
| 35 | <dt>seq</dt> | |
| 36 | <dd> | |
| 37 | The <i>seq</i> to be filtered. | |
| 38 | </dd> | |
| 39 | </dl> | |
| 40 | <h4> | |
| 41 | Remarks | |
| 42 | </h4> | |
| 43 | <div> | |
| 44 | This macro expands <i>pred</i> for each element in <i>seq</i>. It builds | |
| 45 | a new <i>seq</i> out of each element for which <i>pred</i> returns non-zero. | |
| 46 | </div> | |
| 47 | <div> | |
| 48 | For maximum efficiency, use <b>BOOST_PP_SEQ_FILTER_S</b>. | |
| 49 | </div> | |
| 50 | <h4> | |
| 51 | See Also | |
| 52 | </h4> | |
| 53 | <ul> | |
| 54 | <li> | |
| 55 | <a href="limit_mag.html">BOOST_PP_LIMIT_MAG</a></li> | |
| 56 | <li> | |
| 57 | <a href="seq_filter_s.html">BOOST_PP_SEQ_FILTER_S</a></li> | |
| 58 | </ul> | |
| 59 | <h4> | |
| 60 | Requirements | |
| 61 | </h4> | |
| 62 | <div> | |
| 63 | <b>Header:</b> <a href="../headers/seq/filter.html"><boost/preprocessor/seq/filter.hpp></a> | |
| 64 | </div> | |
| 65 | <h4> | |
| 66 | Sample Code | |
| 67 | </h4> | |
| 68 | <div> | |
| 69 | <pre> | |
| 70 | #include <<a href="../headers/comparison/less_equal.html">boost/preprocessor/comparison/less_equal.hpp</a>> | |
| 71 | #include <<a href="../headers/seq/filter.html">boost/preprocessor/seq/filter.hpp</a>> | |
| 72 | ||
| 73 | #define SEQ (1)(3)(2)(5) | |
| 74 | ||
| 75 | #define PRED(s, data, elem) <a href="less_equal.html">BOOST_PP_LESS_EQUAL</a>(elem, data) | |
| 76 | ||
| 77 | <a href="seq_filter.html">BOOST_PP_SEQ_FILTER</a>(PRED, 3, SEQ) | |
| 78 | // expands to (1)(3)(2) | |
| 79 | </pre> | |
| 80 | </div> | |
| 81 | <hr size="1"> | |
| 82 | <div style="margin-left: 0px;"> | |
| 83 |