Boost.Preprocessor

#define BOOST_PP_LIST_FOLD_RIGHT(OP,LIST,STATE)

Iterates OP(D,X,STATE) for each element X of the list LIST (from the right or the end of the list).

In other words, expands to:

OP
( D
, BOOST_PP_LIST_AT(LIST,0)
, ... OP
      ( D
      , BOOST_PP_LIST_AT(LIST,BOOST_PP_SUB(BOOST_PP_LIST_SIZE(LIST),2))
      , OP
        ( D
        , BOOST_PP_LIST_AT(LIST,BOOST_PP_SUB(BOOST_PP_LIST_SIZE(LIST),1))
        , STATE
        )
      ) ...
)

For example,

#define TEST(D,X,STATE) BOOST_PP_CAT(STATE,X)
BOOST_PP_LIST_FOLD_RIGHT(TEST,_,BOOST_PP_TUPLE_TO_LIST(3,(A,B,C)))

expands to:

_CBA

Note

• Folding, or accumulation, is a very general pattern of computation. Most list operations can be implemented in terms of folding.

Test

• list_test.cpp

#define BOOST_PP_LIST_FOLD_RIGHT_D(D,OP,LIST,STATE)

Can be used inside BOOST_PP_WHILE() (see for an explanation of the D parameter).

Note

• BOOST_PP_LIST_FOLD_RIGHT_D() implements automatic recursion. You can use a fold in the OP macro.

#define BOOST_PP_LIST_FOLD_RIGHT_2ND

Obsolete, just use BOOST_PP_LIST_FOLD_RIGHT().

#define BOOST_PP_LIST_FOLD_RIGHT_2ND_D

Obsolete, just use BOOST_PP_LIST_FOLD_RIGHT_D().

Revised

© Copyright Housemarque Oy 2002

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