The BOOST_PP_LIST_CAT_D macro concatenates all elements in a list.  It reenters BOOST_PP_WHILE with maximum efficiency.

Usage

BOOST_PP_LIST_CAT_D(d, list)

Arguments

d
The next available BOOST_PP_WHILE iteration.
list
The list whose elements are to be concatenated.

Remarks

Elements are concatenated left-to-right starting with index 0.

See Also

Requirements

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

Sample Code

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

#define LISTS /* ............. */ \
   ((a, (b, BOOST_PP_NIL)),       \
      ((d, (e, BOOST_PP_NIL)),    \
         ((e, (f, BOOST_PP_NIL)), \
            BOOST_PP_NIL)))       \
   /**/

#define OP(d, state, x) BOOST_PP_CAT(state, BOOST_PP_LIST_CAT_D(d, x))

BOOST_PP_LIST_FOLD_LEFT(OP, _, LISTS) // expands to _abcdef