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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. | |
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>). | |
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>. | |
26 | This macro must return a integral value in the range of <i>0</i> to <b>BOOST_PP_LIMIT_MAG</b>. | |
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>. | |
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> <a href="../headers/list/filter.html"><boost/preprocessor/list/filter.hpp></a> | |
51 | </div> | |
52 | <h4>Sample Code</h4> | |
53 | <div><pre> | |
54 | #include <<a href="../headers/comparison/less_equal.html">boost/preprocessor/comparison/less_equal.hpp</a>> | |
55 | #include <<a href="../headers/list/filter.html">boost/preprocessor/list/filter.hpp</a>> | |
56 | #include <<a href="../headers/list/fold_right.html">boost/preprocessor/list/fold_right.hpp</a>> | |
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 |