Overload C/C++ preprocessor macro on structure of its argument

Question

I would like to write a preprocessor macro that does one thing if it\'s argument is a parenthesized tuple of tokens, like this:

MY_MACRO((x, y))

<

Answer 1

Using boost.preprocessor

#include 
#include 

#define SEQ (w)(x)(y)(z)

#define MACRO(r, data, elem) BOOST_PP_CAT(elem, data)

BOOST_PP_SEQ_FOR_EACH(MACRO, _, SEQ) // expands to w_ x_ y_ z_

It's not exactly the same as even a single argument case requires parenthesis. But It does allow a variable number of parenthesized arguments.

Also a possibility: Use the BOOST_PP_IF, BOOST_PP_EQUAL, and BOOST_PP_TUPLE_ELEM to do something like:

MACRO(1, a)
MACRO(2, (a,b) )
MACRO(3, (a,b,c) )

or so.