Re: [boost] [type_traits] has_equal_to< std::vector<T> > always true_

Subject: Re: [boost] [type_traits] has_equal_to< std::vector<T> > always true_
From: Dave Abrahams (dave_at_[hidden])
Date: 2011-10-21 19:13:19

on Fri Oct 21 2011, Frédéric Bron <frederic.bron-AT-m4x.org> wrote:

>>>>> has_equal_to< Â std::vector<T> Â > Â always returns true
>> Would the Boost.TypeTraits authors consider adding the specializations* to
>> workaround STL not using SFINAE? If not, can these cases be documented?
>
> Hi,
>
> Thanks for highlighting this major issue. I understand that there is
> nothing to do apart from specializing the traits for those particular
> std classes. This would however not work with user classes. As the
> beta is due on Monday, I believe it is too short to submit a working
> and tested patch. Maybe once the beta is out, you can start to work on
> a proposed contribution?

I'm not sure, but it's *conceivable* that with C++11 extended SFINAE it
might be possible to produce a has_equal_to that fails if the operator
can't be instantiated.  Somebody else around here surely knows better
than I do.

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com