1<html> 2<head> 3 <title>BOOST_PP_LIST_FOLD_RIGHT</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</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>). 19 This macro is called for each element in <i>list</i>--each time returning a new <i>state</i>. 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. 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>. 45 There is no longer any such restriction. 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> <a href="../headers/list/fold_right.html"><boost/preprocessor/list/fold_right.hpp></a> 55 </div> 56 <h4>Sample Code</h4> 57<div><pre> 58#include <<a href="../headers/cat.html">boost/preprocessor/cat.hpp</a>> 59#include <<a href="../headers/list/fold_right.html">boost/preprocessor/list/fold_right.hpp</a>> 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> 67 <hr size="1"> 68 <div style="margin-left: 0px;"> 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> 77 </div> 78</body> 79</html> 80