list_fold_right_2nd_d.html 3.2 KB

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  1. <html>
  2. <head>
  3. <title>BOOST_PP_LIST_FOLD_RIGHT_2ND_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_2ND_D</b> macro folds (or accumulates) the elements of a <i>list</i> right-to-left.&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_FOLD_RIGHT_2ND_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>).&nbsp;
  24. This macro is called for each element in <i>list</i>--each time returning a new <i>state</i>.&nbsp;
  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. For the <i>list</i>, (<i>0</i>, (<i>1</i>, (<i>2</i>, <b>BOOST_PP_NIL</b>))), this macro expands to:
  40. <div>
  41. <i>op</i>(<i>d</i>, <i>op</i>(<i>d</i>, <i>op</i>(<i>d</i>, <i>state</i>, <i>0</i>), <i>1</i>), <i>2</i>)
  42. </div>
  43. </div>
  44. <div>
  45. This macro has been superceded by <b>BOOST_PP_LIST_FOLD_RIGHT_<i>d</i></b> and is deprecated.&nbsp;
  46. It only allows a single reentry into <b>BOOST_PP_LIST_FOLD_RIGHT</b>.
  47. </div>
  48. <h4>See Also</h4>
  49. <ul>
  50. <li><a href="list_fold_right.html">BOOST_PP_LIST_FOLD_RIGHT</a></li>
  51. <li><a href="list_fold_right_d.html">BOOST_PP_LIST_FOLD_RIGHT_<i>d</i></a></li>
  52. </ul>
  53. <h4>Requirements</h4>
  54. <div>
  55. <b>Header:</b> &nbsp;<a href="../headers/list/fold_right.html">&lt;boost/preprocessor/list/fold_right.hpp&gt;</a>
  56. </div>
  57. <h4>Sample Code</h4>
  58. <div><pre>
  59. #include &lt;<a href="../headers/cat.html">boost/preprocessor/cat.hpp</a>&gt;
  60. #include &lt;<a href="../headers/list/fold_right.html">boost/preprocessor/list/fold_right.hpp</a>&gt;
  61. #define L1 (a, (b, (c, <a href="nil.html">BOOST_PP_NIL</a>)))
  62. #define L2 (L1, (L1, (L1, <a href="nil.html">BOOST_PP_NIL</a>)))
  63. #define OP(d, state, x) (<a href="list_fold_right_2nd_d.html">BOOST_PP_LIST_FOLD_RIGHT_2ND_D</a>(d, OP_2, _, x), state)
  64. #define OP_2(d, state, x) <a href="cat.html">BOOST_PP_CAT</a>(state, x)
  65. <a href="list_fold_right.html">BOOST_PP_LIST_FOLD_RIGHT</a>(OP, <a href="nil.html">BOOST_PP_NIL</a>, L2)
  66. /*
  67. expands to:
  68. (_cba , (_cba , (_cba , <a href="nil.html">BOOST_PP_NIL</a>)))
  69. */
  70. </pre></div>
  71. <hr size="1">
  72. <div style="margin-left: 0px;">
  73. <i>© Copyright <a href="http://www.housemarque.com" target="_top">Housemarque Oy</a> 2002</i>
  74. </br><i>© Copyright Paul Mensonides 2002</i>
  75. </div>
  76. <div style="margin-left: 0px;">
  77. <p><small>Distributed under the Boost Software License, Version 1.0. (See
  78. accompanying file <a href="../../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or
  79. copy at <a href=
  80. "http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a>)</small></p>
  81. </div>
  82. </body>
  83. </html>