RE: [boost] Suggested extension to the preprocessor library

From: Paul Mensonides (pmenso57_at_[hidden])
Date: 2004-12-01 19:00:07

> -----Original Message-----
> From: boost-bounces_at_[hidden] 
> [mailto:boost-bounces_at_[hidden]] On Behalf Of Ryan Saunders

Hi Ryan.

>      typedef typename meta_func< typename T0::inner_type, 
> typename T1::inner_type, typename T2::inner_type>::type;
> 
> I don't see a way to do this with any of the ENUM_XXX macros. 
> Maybe something like ENUM_SPLIT_PARAMS(COUNT, PREF, SUFF) 
> that would generate PREF ## n ## SUFF?

The ENUM_BINARY_PARAMS is the general form for this kind of stuff.  You
typically use it with INTERCEPT, such as:

#include <boost/preprocessor/facilities/intercept.hpp>
#include <boost/preprocessor/repetition/enum_binary_params.hpp>

BOOST_PP_ENUM_BINARY_PARAMS(
    3, typename T, ::inner_type BOOST_PP_INTERCEPT
)

INTERCEPT (unsurpisingly) intercepts the numeric concatenation and expands to
nothing.

Normally the library avoids macros that have very specific uses.  In fact,
ENUM_PARAMS and ENUM_BINARY_PARAMS are probably the two most domain-specific
macros in the library.  If the usage scenario is too complex for ENUM_PARAMS or
ENUM_BINARY_PARAMS (possibly with INTERCEPT), then you need to use the much more
general form, ENUM.

Regards,
Paul Mensonides