ceph/src/boost/libs/preprocessor/doc/ref/list_fold_left_2nd_d.html

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   3         <title>BOOST_PP_LIST_FOLD_LEFT_2ND_D</title>
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   8                 The <b>BOOST_PP_LIST_FOLD_LEFT_2ND_D</b> macro folds (or accumulates) the elements of a <i>list</i> left-to-right.&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_LEFT_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_LEFT</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  45                         This macro has been superceded by 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_LEFT_<i>d</i></b> and is deprecated.&nbsp;
  46                         It only allows a single reentry into <b>BOOST_PP_LIST_FOLD_LEFT</b>.
  47                 </div>
  48         <h4>See Also</h4>
  49                 <ul>
  50                         <li><a href="list_fold_left.html">BOOST_PP_LIST_FOLD_LEFT</a></li>
  51                         <li><a href="list_fold_left_d.html">BOOST_PP_LIST_FOLD_LEFT_<i>d</i></a></li>
  52                 </ul>
  53         <h4>Requirements</h4>
  54                 <div>
  55                         <b>Header:</b> &nbsp;<a href="../headers/list/fold_left.html">&lt;boost/preprocessor/list/fold_left.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_left.html">boost/preprocessor/list/fold_left.hpp</a>&gt;
  61
  62 #define L1 (a, (b, (c, <a href="nil.html">BOOST_PP_NIL</a>)))
  63 #define L2 (L1, (L1, (L1, <a href="nil.html">BOOST_PP_NIL</a>)))
  64
  65 #define OP(d, state, x) (<a href="list_fold_left_2nd_d.html">BOOST_PP_LIST_FOLD_LEFT_2ND_D</a>(d, OP_2, _, x), state)
  66 #define OP_2(d, state, x) <a href="cat.html">BOOST_PP_CAT</a>(state, x)
  67
  68 <a href="list_fold_left.html">BOOST_PP_LIST_FOLD_LEFT</a>(OP, <a href="nil.html">BOOST_PP_NIL</a>, L2)
  69 /*
  70    expands to:
  71    (_abc , (_abc , (_abc , <a href="nil.html">BOOST_PP_NIL</a>)))
  72 */
  73 </pre></div>
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  76                 <i>© Copyright <a href="http://www.housemarque.com" target="_top">Housemarque Oy</a> 2002</i>
  77                 </br><i>© Copyright Paul Mensonides 2002</i>
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  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>
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