Re: [boost] [type_traits] Rewrite and dependency free version

Subject: Re: [boost] [type_traits] Rewrite and dependency free version
From: Peter Dimov (lists_at_[hidden])
Date: 2015-01-15 12:55:51

Agustín K-ballo Bergé wrote:
> On 1/15/2015 11:34 AM, Peter Dimov wrote:
> > Ion Gaztañaga wrote:
> >
> >> In any case with my alternative implementation you could avoid even 
> >> Boost.PP for manteinance and avoid all those overloads.
> >
> > My first thought when looking at is_function was also to suggest 
> > "is_convertible<T&,T*>", but then I saw that Ion has already got to it 
> > first, complete with the nullptr_t check.
>
> This doesn't quite work as `void() const`, and any other combination of cv 
> and ref qualifiers, is a function type but cannot be instantiated.

You're right. The current PP-based implementation doesn't catch those 
either, though. Fortunately, if a compiler supports 'void () const &&', it 
probably has std::is_function as well, so we can just use that. :-)

Although, now that I think of it, creating 'void() const' is in principle 
possible in C++03 as well. Not sure what the old type traits did with such 
types.