The BOOST_PP_LIST_FOLD_RIGHT_D macro folds (or accumulates) the elements of a list right-to-left.  It reenters BOOST_PP_WHILE with maximum efficiency.

Usage

BOOST_PP_LIST_FOLD_RIGHT_D(d, op, state, list)

Arguments

d
The next available BOOST_PP_WHILE iteration.
op
A ternary operation of the form op(d, state, elem).  This macro is called for each element in list--each time returning a new state.  This operation is expanded by BOOST_PP_LIST_FOLD_RIGHT with the next available BOOST_PP_WHILE iteration, the current state, and the current element.
state
The initial state of the fold.
list
The list to be folded.

Remarks

This macro does not have the same signature as it previously did.  The arguments have been swapped to provide a uniform interface with BOOST_PP_LIST_FOLD_LEFT.
For the list, (0, (1, (2, BOOST_PP_NIL))), this macro expands to:
op(d, op(d, op(d, state, 2), 1), 0)
This macro has been superceded by BOOST_PP_LIST_FOLD_RIGHT_d and is deprecated.  It only allows a single reentry into BOOST_PP_LIST_FOLD_RIGHT.

See Also

Requirements

Header:  <boost/preprocessor/list/fold_right.hpp>

Sample Code

#include <boost/preprocessor/cat.hpp>
#include <boost/preprocessor/list/fold_right.hpp>

#define L1 (a, (b, (c, BOOST_PP_NIL)))
#define L2 (L1, (L1, (L1, BOOST_PP_NIL)))

#define OP(d, state, x) (BOOST_PP_LIST_FOLD_RIGHT_D(d, OP_2, _, x), state)
#define OP_2(d, state, x) BOOST_PP_CAT(state, x)

BOOST_PP_LIST_FOLD_RIGHT(OP, BOOST_PP_NIL, L2)
/*
   expands to:
   (_cba, (_cba, (_cba, BOOST_PP_NIL)))
*/

Copyright Housemarque Oy 2002
Copyright Paul Mensonides 2002

Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at www.boost.org/LICENSE_1_0.txt)