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

From: Roman Perepelitsa (roman.perepelitsa_at_[hidden])
Date: 2007-06-18 02:55:50

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