Re: [boost] Re: Formal Review: FOREACH macro

From: Stefan Strasser (sstrasser_at_[hidden])
Date: 2005-04-25 16:55:18

michael toksvig schrieb:
>>What is your evaluation of the documentation?
> 
> 
> describe pitfalls, if any. actually, there is one pitfall:
> 
> BOOST_FOREACH(pair<Key, Value> &p, some_map)
> 
> does not work, since the preprocessor just can't get over that first comma
> 

this could be worked around with C99 variadic macros if available, 
something like:

#define _BOOST_FOREACH2(a1,a2,...) BOOST_FOREACH2(a1,a2)
#define _BOOST_FOREACH3(a1,a2,a3,...) BOOST_FOREACH3(a1,a2,a3)
// ...

#define _BOOST_FOREACH(a1,a2,a3,a4,a5,a6,a7,a8,a9,nr,...) 
_BOOST_FOREACH##nr(a1,a2,a3,a4,a5,a6,a7,a8,a9)

#define BOOST_FOREACH(...) _BOOST_FOREACH(__VA_ARGS__,9,8,7,6,5,4,3,2,1)

-- 
Stefan Strasser