C++0x Concepts - Dead?

[BLS]

Walter Bright wrote:
> BLS wrote:
>> The current Template specialization implementation is doing a best fit 
>> search anyway, so why constraints are not able to use the same 
>> mechanism. ?
> 
> The template specialization method is based on types - but there's no 
> way to look inside those types and specialize based on properties of 
> those types. That's where constraints come in.
> 
> Constraints use a completely different matching method than the type 
> parameters do. It makes intuitive sense to logically separate them, 
> rather than to mix them up.
> 


Thanks for taking the time to answer ; But the question remains the same 
: _Why_ ? Constraints /have/ to use a completely different approach ?

("more intuitive than" is not ..ahem.. is not a good enough reason)

> 
>> bearophile brings in several times Scala/OCAML like pattern matching. 
>> Why not using that for constraints ?
> 
> I have no idea how that works, though Bartosz has been looking into it.

O well, I am pretty sure that bearophile is willing to give you any 
information you need  :)