projects / ceph.git / blame
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|---|---|---|
| 7c673cae FG |
1 | <html> |
| 2 | <head> | |
| 3 | <title>BOOST_PP_LIST_FOLD_RIGHT_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_FOLD_RIGHT_D</b> macro folds (or accumulates) the elements of a <i>list</i> right-to-left. | |
| 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_FOLD_RIGHT_D</b>(<i>d</i>, <i>op</i>, <i>state</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>op</dt> | |
| 22 | <dd> | |
| 23 | A ternary operation of the form <i>op</i>(<i>d</i>, <i>state</i>, <i>elem</i>). | |
| 24 | This macro is called for each element in <i>list</i>--each time returning a new <i>state</i>. | |
| 25 | This operation is expanded by <b>BOOST_PP_LIST_FOLD_RIGHT</b> with the next available <b>BOOST_PP_WHILE</b> iteration, | |
| 26 | the current <i>state</i>, and the current element. | |
| 27 | </dd> | |
| 28 | <dt>state</dt> | |
| 29 | <dd> | |
| 30 | The initial state of the fold. | |
| 31 | </dd> | |
| 32 | <dt>list</dt> | |
| 33 | <dd> | |
| 34 | The <i>list</i> to be folded. | |
| 35 | </dd> | |
| 36 | </dl> | |
| 37 | <h4>Remarks</h4> | |
| 38 | <div> | |
| 39 | This macro does not have the same signature as it previously did. | |
| 40 | The arguments have been swapped to provide a uniform interface with <b>BOOST_PP_LIST_FOLD_LEFT</b>. | |
| 41 | </div> | |
| 42 | <div> | |
| 43 | For the <i>list</i>, (<i>0</i>, (<i>1</i>, (<i>2</i>, <b>BOOST_PP_NIL</b>))), this macro expands to: | |
| 44 | <div> | |
| 45 | <i>op</i>(<i>d</i>, <i>op</i>(<i>d</i>, <i>op</i>(<i>d</i>, <i>state</i>, <i>2</i>), <i>1</i>), <i>0</i>) | |
| 46 | </div> | |
| 47 | </div> | |
| 48 | <div> | |
| 49 | This macro has been superceded by <b>BOOST_PP_LIST_FOLD_RIGHT_<i>d</i></b> and is deprecated. | |
| 50 | It only allows a single reentry into <b>BOOST_PP_LIST_FOLD_RIGHT</b>. | |
| 51 | </div> | |
| 52 | <h4>See Also</h4> | |
| 53 | <ul> | |
| 54 | <li><a href="list_fold_right.html">BOOST_PP_LIST_FOLD_RIGHT</a></li> | |
| 55 | <li><a href="list_fold_right_d.html">BOOST_PP_LIST_FOLD_RIGHT_<i>d</i></a></li> | |
| 56 | </ul> | |
| 57 | <h4>Requirements</h4> | |
| 58 | <div> | |
| 59 | <b>Header:</b> <a href="../headers/list/fold_right.html"><boost/preprocessor/list/fold_right.hpp></a> | |
| 60 | </div> | |
| 61 | <h4>Sample Code</h4> | |
| 62 | <div><pre> | |
| 63 | #include <<a href="../headers/cat.html">boost/preprocessor/cat.hpp</a>> | |
| 64 | #include <<a href="../headers/list/fold_right.html">boost/preprocessor/list/fold_right.hpp</a>> | |
| 65 | ||
| 66 | #define L1 (a, (b, (c, <a href="nil.html">BOOST_PP_NIL</a>))) | |
| 67 | #define L2 (L1, (L1, (L1, <a href="nil.html">BOOST_PP_NIL</a>))) | |
| 68 | ||
| 69 | #define OP(d, state, x) (<a href="list_fold_right_d_old.html">BOOST_PP_LIST_FOLD_RIGHT_D</a>(d, OP_2, _, x), state) | |
| 70 | #define OP_2(d, state, x) <a href="cat.html">BOOST_PP_CAT</a>(state, x) | |
| 71 | ||
| 72 | <a href="list_fold_right.html">BOOST_PP_LIST_FOLD_RIGHT</a>(OP, <a href="nil.html">BOOST_PP_NIL</a>, L2) | |
| 73 | /* | |
| 74 | expands to: | |
| 75 | (_cba, (_cba, (_cba, <a href="nil.html">BOOST_PP_NIL</a>))) | |
| 76 | */ | |
| 77 | </pre></div> | |
| 78 | <hr size="1"> | |
| 79 | <div style="margin-left: 0px;"> | |
| 80 |