Example of Definition of Value Specified ENUM with Boost.PP

boost_pp_valued_enum.cpp

#include <iostream>
#include <boost/preprocessor.hpp>

#define VALUED_ENUM(unused, index, seq)                         \
  BOOST_PP_TUPLE_ELEM(2, 0, BOOST_PP_SEQ_ELEM(index, seq))      \
  = BOOST_PP_TUPLE_ELEM(2, 1, BOOST_PP_SEQ_ELEM(index, seq))

#define INSERT_TUPLE_HEAD(s, state, elem)                   \
  BOOST_PP_SEQ_PUSH_BACK(state,                             \
                         BOOST_PP_TUPLE_ELEM(2, 0, elem))

#define ENUM_TO_STR(unused, data, elem)             \
  case BOOST_PP_CAT(data, elem):                    \
  std::cerr << BOOST_PP_STRINGIZE(elem) << "\n";    \
  break;

#define ENUM_KEY_VALUE ((VAL_A,0x3))((VAL_B,0x1))((VAL_C,0x4))

#define ENUM_KEY_TMP BOOST_PP_SEQ_FOLD_LEFT(INSERT_TUPLE_HEAD,  \
                                            (),                 \
                                            ENUM_KEY_VALUE)

#define ENUM_KEY BOOST_PP_SEQ_REST_N(1, ENUM_KEY_TMP)

enum TestEnum {
  BOOST_PP_ENUM(BOOST_PP_SEQ_SIZE(ENUM_KEY_VALUE), \
                VALUED_ENUM, ENUM_KEY_VALUE)
};

int main()
{
  for(int i=1; i < 5; ++i)
  {
    switch(i)
    {
      BOOST_PP_SEQ_FOR_EACH(ENUM_TO_STR, , ENUM_KEY);
    default:
      std::cerr << "(no hit)" << "\n";
    }
  }
}