Can someone test the following preprocessor code on the Sun and IBM preprocessors: #include <boost/preprocessor/detail/split.hpp> #include <boost/preprocessor/punctuation/comma.hpp> #include <boost/preprocessor/punctuation/paren.hpp> #include <boost/preprocessor/tuple/eat.hpp> #define IS_NULLARY(x) \ BOOST_PP_SPLIT(1, IS_NULLARY_C x BOOST_PP_COMMA() 0) \ /**/ #define IS_NULLARY_C() \ ~, 1 BOOST_PP_RPAREN() \ BOOST_PP_TUPLE_EAT(2) BOOST_PP_LPAREN() ~ \ /**/ IS_NULLARY(()) // 1 IS_NULLARY(()abc) // 1 IS_NULLARY(+) // 0 IS_NULLARY(xyz) // 0 #define IS_UNARY(x) IS_NULLARY(IS_UNARY_C x) #define IS_UNARY_C(a) () IS_UNARY((a)) // 1 IS_UNARY((a)abc) // 1 IS_UNARY(+) // 0 IS_UNARY(xyz) // 0 Regards and thanks, Paul Mensonides