#include <boost/preprocessor/array/push_back.hpp>
#include <boost/preprocessor/stringize.hpp>
#include <boost/preprocessor/tuple/rem.hpp>
#include <iostream>

#define ARRAY (3, (a, b, c))
#define EMPTY_ARRAY (0, ())

int main()
{
    std::cout << BOOST_PP_STRINGIZE(BOOST_PP_ARRAY_PUSH_BACK(ARRAY, d)) << std::endl; // expands to (4, (a, b, c, d))
    std::cout << BOOST_PP_STRINGIZE(BOOST_PP_ARRAY_PUSH_BACK(EMPTY_ARRAY, d)) << std::endl; // expands to (4, (a, b, c, d))
}