How do I expand a macro containing commas inside a BOOST_PP_IF

Question

I asked the following question earlier, but the solution doesn\'t seem to work in this particular case.

How do I print out a comma multiple times using Boost Preprocesso

Answer 1

It turns out that you can do this without __VA_ARGS__. In this simple example I used a comma which is in the template argument of function toString() Working demo:

#include 
#include 
#include 
#include 

#define SEQUENCE (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)

#define IGNORE_ARG(arg)
#define GET_NAME(data) BOOST_PP_SEQ_ELEM(0, data)
#define GET_BELOW(data) BOOST_PP_SEQ_ELEM(1, data)

#define PARSE_SEQUENCE(r, data, elem)                  \
    BOOST_PP_IF(                                       \
        BOOST_PP_GREATER_EQUAL(elem, GET_BELOW(data)), \
            GET_NAME(data), IGNORE_ARG)                \
    (elem)

#define SKIP_NUMBERS_BELOW(name, below)                \
    BOOST_PP_SEQ_FOR_EACH(PARSE_SEQUENCE, (name)(below), SEQUENCE)

#define TEST(name) SKIP_NUMBERS_BELOW(name, 4)

#define MACRO_CONTAINING_COMMA(N) toString() <<

template  // whatever, I just need a comma here.
std::string toString() {
    return boost::lexical_cast(a) + ":" + boost::lexical_cast(b) + " ";
}

int main() {
    std::cout << TEST(MACRO_CONTAINING_COMMA) "\n";
}