#include <boost/preprocessor.hpp>
#include <iostream>
 
#define COMBINE(index, data, elem) (BOOST_PP_STRINGIZE(elem))(".")
 
#define API_METHOD(args) BOOST_PP_SEQ_CAT(args)
#define INSERT_SEPARATOR(args, sep) BOOST_PP_SEQ_REVERSE(BOOST_PP_SEQ_TAIL(BOOST_PP_SEQ_REVERSE(BOOST_PP_SEQ_FOR_EACH(COMBINE, sep, args))))
 
#define FLATTEN_SEQ_HELPER(index, data, elem) elem
#define FLATTEN_SEQ(args) BOOST_PP_SEQ_FOR_EACH(FLATTEN_SEQ_HELPER, _, args)
 
#define JOIN(args, sep) FLATTEN_SEQ(INSERT_SEPARATOR(args, sep))
 
 
int main()
{
    std::cout << JOIN((a)(b)(c), ".") << std::endl;
}

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