Re: [Boost-users] [preprocessor] Argument list conversion

18 Jun 2007


      Tobias Schwinger <tschwinger <at> isonews2.com> writes:
...
Yep, here's another dirty trick :
#include <boost/preprocessor/detail/is_unary.hpp>
#define SPECIAL (whatever)
     #define IS_SPECIAL BOOST_PP_IS_UNARY
IS_SPECIAL(a)         // 0
     IS_SPECIAL(b)         // 0
     IS_SPECIAL(SPECIAL)   // 1
It isn't entirely portable to older preprocessors (that's why this code 
lives in preprocessor/detail) but should work with latest versions of 
the widely-used compilers.
This also works:

#include <boost/preprocessor/facilities/is_empty.hpp>
#include <boost/preprocessor/empty.hpp>

#define SPECIAL
#define IS_SPECIAL(x) BOOST_PP_IS_EMPTY(BOOST_PP_EMPTY() x)

Roman Perepelitsa