| <html> |
| <head> |
| <title>BOOST_PP_LIST_FOLD_LEFT_D</title> |
| <link rel="stylesheet" type="text/css" href="../styles.css"> |
| </head> |
| <body> |
| <div style="margin-left: 0px;"> |
| The <b>BOOST_PP_LIST_FOLD_LEFT_D</b> macro folds (or accumulates) the elements of a <i>list</i> left-to-right. |
| It reenters <b>BOOST_PP_WHILE</b> with maximum efficiency. |
| </div> |
| <h4>Usage</h4> |
| <div class="code"> |
| <b>BOOST_PP_LIST_FOLD_LEFT_D</b>(<i>d</i>, <i>op</i>, <i>state</i>, <i>list</i>) |
| </div> |
| <h4>Arguments</h4> |
| <dl> |
| <dt>d</dt> |
| <dd> |
| The next available <b>BOOST_PP_WHILE</b> iteration. |
| </dd> |
| <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_LEFT</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> |
| 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>0</i>), <i>1</i>), <i>2</i>) |
| </div> |
| </div> |
| <div> |
| This macro has been superceded by <b>BOOST_PP_LIST_FOLD_LEFT_<i>d</i></b> and is deprecated. |
| It only allows a single reentry into <b>BOOST_PP_LIST_FOLD_LEFT</b>. |
| </div> |
| <h4>See Also</h4> |
| <ul> |
| <li><a href="list_fold_left.html">BOOST_PP_LIST_FOLD_LEFT</a></li> |
| <li><a href="list_fold_left_d.html">BOOST_PP_LIST_FOLD_LEFT_<i>d</i></a></li> |
| </ul> |
| <h4>Requirements</h4> |
| <div> |
| <b>Header:</b> <a href="../headers/list/fold_left.html"><boost/preprocessor/list/fold_left.hpp></a> |
| </div> |
| <h4>Sample Code</h4> |
| <div><pre> |
| #include <<a href="../headers/cat.html">boost/preprocessor/cat.hpp</a>> |
| #include <<a href="../headers/list/fold_left.html">boost/preprocessor/list/fold_left.hpp</a>> |
| |
| #define L1 (a, (b, (c, <a href="nil.html">BOOST_PP_NIL</a>))) |
| #define L2 (L1, (L1, (L1, <a href="nil.html">BOOST_PP_NIL</a>))) |
| |
| #define OP(d, state, x) (<a href="list_fold_left_d_old.html">BOOST_PP_LIST_FOLD_LEFT_D</a>(d, OP_2, _, x), state) |
| #define OP_2(d, state, x) <a href="cat.html">BOOST_PP_CAT</a>(state, x) |
| |
| <a href="list_fold_left.html">BOOST_PP_LIST_FOLD_LEFT</a>(OP, <a href="nil.html">BOOST_PP_NIL</a>, L2) |
| /* |
| expands to: |
| (_abc, (_abc, (_abc, <a href="nil.html">BOOST_PP_NIL</a>))) |
| */ |
| </pre></div> |
| <hr size="1"> |
| <div style="margin-left: 0px;"> |
| <i>© Copyright <a href="http://www.housemarque.com" target="_top">Housemarque Oy</a> 2002</i> |
| </br><i>© Copyright Paul Mensonides 2002</i> |
| </div> |
| <div style="margin-left: 0px;"> |
| <p><small>Distributed under the Boost Software License, Version 1.0. (See |
| accompanying file <a href="../../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or |
| copy at <a href= |
| "http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a>)</small></p> |
| </div> |
| </body> |
| </html> |
