<html> <head> <title>BOOST_PP_LIST_FOLD_RIGHT</title> <link rel="stylesheet" type="text/css" href="../styles.css"> </head> <body> <div style="margin-left: 0px;"> The <b>BOOST_PP_LIST_FOLD_RIGHT</b> macro folds (or accumulates) the elements of a <i>list</i> right-to-left. </div> <h4>Usage</h4> <div class="code"> <b>BOOST_PP_LIST_FOLD_RIGHT</b>(<i>op</i>, <i>state</i>, <i>list</i>) </div> <h4>Arguments</h4> <dl> <dt>op</dt> <dd> A ternary operation of the form <i>op</i>(<i>d</i>, <i>state</i>, <i>elem</i>). This macro is called for each element in <i>list</i>--each time returning a new <i>state</i>. This operation is expanded by <b>BOOST_PP_LIST_FOLD_RIGHT</b> with the next available <b>BOOST_PP_WHILE</b> iteration, the current <i>state</i>, and the current element. </dd> <dt>state</dt> <dd> The initial state of the fold. </dd> <dt>list</dt> <dd> The <i>list</i> to be folded. </dd> </dl> <h4>Remarks</h4> <div> This macro does not have the same signature as it previously did. The arguments have been swapped to provide a uniform interface with <b>BOOST_PP_LIST_FOLD_LEFT</b>. </div> <div> For the <i>list</i>, (<i>0</i>, (<i>1</i>, (<i>2</i>, <b>BOOST_PP_NIL</b>))), this macro expands to: <div> <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>) </div> </div> <div> Previously, this macro could not be used inside <b>BOOST_PP_WHILE</b>. There is no longer any such restriction. It is more efficient, however, to use <b>BOOST_PP_LIST_FOLD_RIGHT_<i>d</i></b> in such a situation. </div> <h4>See Also</h4> <ul> <li><a href="list_fold_right_d.html">BOOST_PP_LIST_FOLD_RIGHT_<i>d</i></a></li> </ul> <h4>Requirements</h4> <div> <b>Header:</b> <a href="../headers/list/fold_right.hpp.html"><boost/preprocessor/list/fold_right.hpp></a> </div> <h4>Sample Code</h4> <div><pre> #include <<a href="../headers/cat.hpp.html">boost/preprocessor/cat.hpp</a>> #include <<a href="../headers/list/fold_right.hpp.html">boost/preprocessor/list/fold_right.hpp</a>> #define LIST (a, (b, (c, <a href="nil.html">BOOST_PP_NIL</a>))) #define OP(d, state, x) <a href="cat.html">BOOST_PP_CAT</a>(state, x) <a href="list_fold_right.html">BOOST_PP_LIST_FOLD_RIGHT</a>(OP, _, LIST) // expands to _cba </pre></div> </body> </html>
