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

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   3         <title>BOOST_PP_LIST_FOLD_RIGHT</title>
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   8                 The <b>BOOST_PP_LIST_FOLD_RIGHT</b> macro folds (or accumulates) the elements of a <i>list</i> right-to-left.
   9         </div>
  10         <h4>Usage</h4>
  11                 <div class="code">
  12                         <b>BOOST_PP_LIST_FOLD_RIGHT</b>(<i>op</i>, <i>state</i>, <i>list</i>)
  13                 </div>
  14         <h4>Arguments</h4>
  15                 <dl>
  16                         <dt>op</dt>
  17                         <dd>
  18                                 A ternary operation of the form <i>op</i>(<i>d</i>, <i>state</i>, <i>elem</i>).&nbsp;
  19                                 This macro is called for each element in <i>list</i>--each time returning a new <i>state</i>.&nbsp;
  20                                 This operation is expanded by <b>BOOST_PP_LIST_FOLD_RIGHT</b> with the next available <b>BOOST_PP_WHILE</b> iteration,
  21                                 the current <i>state</i>, and the current element.
  22                         </dd>
  23                         <dt>state</dt>
  24                         <dd>
  25                                 The initial state of the fold.
  26                         </dd>
  27                         <dt>list</dt>
  28                         <dd>
  29                                 The <i>list</i> to be folded.
  30                         </dd>
  31                 </dl>
  32         <h4>Remarks</h4>
  33                 <div>
  34                         This macro does not have the same signature as it previously did.&nbsp;
  35                         The arguments have been swapped to provide a uniform interface with <b>BOOST_PP_LIST_FOLD_LEFT</b>.
  36                 </div>
  37                 <div>
  38                         For the <i>list</i>, (<i>0</i>, (<i>1</i>, (<i>2</i>, <b>BOOST_PP_NIL</b>))), this macro expands to:
  39                         <div>
  40                                 <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>)
  41                         </div>
  42                 </div>
  43                 <div>
  44                         Previously, this macro could not be used inside <b>BOOST_PP_WHILE</b>.&nbsp;
  45                         There is no longer any such restriction.&nbsp;
  46                         It is more efficient, however, to use <b>BOOST_PP_LIST_FOLD_RIGHT_<i>d</i></b> in such a situation.
  47                 </div>
  48         <h4>See Also</h4>
  49                 <ul>
  50                         <li><a href="list_fold_right_d.html">BOOST_PP_LIST_FOLD_RIGHT_<i>d</i></a></li>
  51                 </ul>
  52         <h4>Requirements</h4>
  53                 <div>
  54                         <b>Header:</b> &nbsp;<a href="../headers/list/fold_right.html">&lt;boost/preprocessor/list/fold_right.hpp&gt;</a>
  55                 </div>
  56         <h4>Sample Code</h4>
  57 <div><pre>
  58 #include &lt;<a href="../headers/cat.html">boost/preprocessor/cat.hpp</a>&gt;
  59 #include &lt;<a href="../headers/list/fold_right.html">boost/preprocessor/list/fold_right.hpp</a>&gt;
  60
  61 #define LIST (a, (b, (c, <a href="nil.html">BOOST_PP_NIL</a>)))
  62
  63 #define OP(d, state, x) <a href="cat.html">BOOST_PP_CAT</a>(state, x)
  64
  65 <a href="list_fold_right.html">BOOST_PP_LIST_FOLD_RIGHT</a>(OP, _, LIST) // expands to _cba
  66 </pre></div>
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  69                 <i>© Copyright <a href="http://www.housemarque.com" target="_top">Housemarque Oy</a> 2002</i>
  70                 </br><i>© Copyright Paul Mensonides 2002</i>
  71         </div>
  72         <div style="margin-left: 0px;">
  73                 <p><small>Distributed under the Boost Software License, Version 1.0. (See
  74                 accompanying file <a href="../../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or
  75                 copy at <a href=
  76                 "http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a>)</small></p>
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