RE: [boost] select_type.hpp

From: Aleksey Gurtovoy (alexy_at_[hidden])
Date: 2001-11-20 13:03:43

Andrei Alexandrescu wrote:
> I think if_true in select_type ought to become a first-class 
> citizen. It's useful enough to everyone.
> 
> I also suggest including the friendlier version:
> 
>     template <bool flag, typename T, typename U>
>     struct select
>     {
>         typedef T type;
>     };
>     template <typename T, typename U>
>     struct Select<false, T, U>
>     {
>         typedef U type;
>     };
> 
> for compilers that support partial specialization. The if_true is
> compiler-friendlier but considerably harder to use (that 
> "template" in the middle of it is really annoying).

Please take a look at "boost/mpl/select_type.hpp" header - it already has
'select_type' template that is equivalent to what you propose above, and
also 'select_type_t' variation, which is mainly a workaround for broken
compilers, but, sadly, is useful much more often than one would like it to
be.

--
Aleksey