Re: Classification of template typename labels?

From: rogeeff (rogeeff_at_[hidden])
Date: 2002-01-20 12:22:01

--- In boost_at_y..., "Ralf W. Grosse-Kunstleve" <rwgk_at_y...> wrote:
> (This question is related to my previous posting.)
> 
> Here is something I am often wondering about:
> 
> template <typename NumVectorType>
> NumVectorType operator*(const NumVectorType& lhs, const 
NumVectorType& rhs);
> 
> Is there a way to classify or register types as NumVectorTypes?
> 
> I know how to make a distinction between types once I am
> /inside/ the function (using traits). However, what I am
> after is something like:
> 
> tell_compiler {
>   possible typename NumType:
>     double
>     float
>     etc.
>   possible typename NumVectorType:
>     std::vector<NumType>
>     boost::array<NumType, *>
>     etc.
> }
> 
> Then the compiler should select template functions only if the
> concrete type is registered under the typename label.
> 
> Is this asking for a formalization of "concepts?"
> To which degree can this be emulated with the language as-is?
> What can we expect in the future (from the standard committee)?
> 
> Thanks,
>         Ralf

I was thinking in this direction some time ago. The closest thing I 
found is to define partial specialization by type list. But I did not 
find a way to define automatically all specialization by given 
typelist T and template definition foo<t>. For example, 
  if T = int, fload, double 

then I want to write foo<T> and compiler should understand it like 
foo<int>
foo<float>
foo<double>

Does anybode know the MP solution (if there is one)? 

Gennadiy.