Re: [boost] Re: enable_if review

From: Gabriel Dos Reis (gdr_at_[hidden])
Date: 2003-10-10 13:29:58

Jaakko Jarvi <jajarvi_at_[hidden]> writes:

| In our last exciting episode David Abrahams wrote:
| > > 1. lazy_enable_if
| > >
| > > Shouldn't be this named apply_enable_if. It very similar to the appropriate
| > > MPL concept and seems logical to be named the same.
| 
| > I had the same thought, FWIW.  I just couldn't make it sound right in
| > the ear, though.  
| 
| > On second thought, I wonder if we need it at all.  Isn't 
| 
| >    mpl::apply_if<condition, nullary_metafunction, disabled>::type
| 
| > equivalent, where disabled is a struct with no nested ::type?
| 
| This wouldn't work. At the outermost level (apply_if), ::type always
| exists, so this would lead to an error, not disabling the function, on
| compilers (e.g. g++) where SFINAE is not applied when the invalid type
| occurs nested in another instantiation.

Jaakko --

  I'm trying to catch up with this thread.  Please could you elaborate
on the problem with g++ here? 

Thanks,

-- Gaby