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

18 Jun 2007


      Roman Perepelitsa wrote:
...
Tobias Schwinger  writes:
...
Yep, here's another dirty trick :
#include 
#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 
#include 
#define SPECIAL
#define IS_SPECIAL(x) BOOST_PP_IS_EMPTY(BOOST_PP_EMPTY() x)
Yep, that's even better as it allows x to be anything. Got some idea how 
portable it is?

Regards,
Tobias