On Wed, Jun 29, 2011 at 10:54 AM, Edward Diener <eldiener@tropicsoft.com> wrote:
Nonetheless macros using variadics to identify pp-lib data types on the fly might still be useful and I have already come up with a pretty good IS_TUPLE. Whether an IS_ARRAY, IS_LIST, or IS_SEQ is posible I shall see.
Useful indeed. I have implemented some sort of IS_TUPLE within Boost.Local. BOOST_LOCAL_PARAMS() uses it to accept both the follow syntaxes when variadics are present: BOOST_LOCAL_PARAMS(int x, int& y) // (1) BOOST_LOCAL_PARAMS( (int x) (int& y) ) // (2) Essentially (going by memory): #if BOOST_VARIADICS_MACRO #define BOOST_LOCAL_PARAMS(...) \ BOOST_PP_IIF(IS_TUPLE(__VA_ARGS__), \ BOOST_LOCAL_PARAMS_TUPLE_ /* for (1) */ \ , \ BOOST_LOCAL_PARAMS_SEQ_ /* for (2) */ \ )(__VA_ARGS__) #else // variadics #define BOOST_LOCAL_PARAMS(seq) BOOST_LOCAL_PARAMS_SEQ_(seq) // only (2) :( #endif // variadics
I will probably end up putting any additions in my VMD library for the time being and if Paul decides that he wants them for pp-lib sometime in the future they will eventually go there.
I'd prefer to see IS_TUPLE (and possibly all IS_XXX) as part of these Boost.Preprocess variadics changes. --Lorenzo