[boost] [preprocessor] question

This is regarding to BOOST_PP_IS_NULLARY macro. I would like to use it with only 2 types of inputs: 1. Empty parenthesis: () 2. Plain C++ identifier within parenthesis: (identifier) With this input restrictions, is it safe to use BOOST_PP_IS_NULLARY in portable code that must be compiled in different platforms? Thanks in advance. Jorge