Partial template specialization with multiple template parameter packs

Question

Continuing my journey into the world of variadic templates, I encountered another problem.

Assuming the following template class:

template < typename          


        

Answer 1

Probably this answer won't clear your question directly, but the following code compiled on ideone(gcc-4.5.1) when I tested.

#include <cstdio>
#include <tuple>

template< class, class > struct S {
  S() { puts("primary"); }
};

template<
  template< class... > class T, class...TArgs
, template< class... > class U, class...UArgs
>
struct S< T< TArgs... >, U< UArgs... > > {
  S() { puts("specialized"); }
};

int main()
{
  S< int, int >  p;                                       // "primary"
  S< std::tuple< int, char >, std::tuple< float > >  s;   // "specialised"
}

I'm not sure this code is strictly conformant, but as far as I read N3225 14.5.3, I couldn't find the statement which mentions that template parameter pack has to be the last template parameter.

Edit:
I reread N3225 and found the following statements:

8.3.5/4 If the parameter-declaration-clause terminates with an ellipsis or a function parameter pack (14.5.3), the number of arguments shall be equal to or greater than the number of parameters that do not have a default argument and are not function parameter packs.

14.8.2.5/10 [Note: A function parameter pack can only occur at the end of a parameter-declarationlist(8.3.5). -end note]

So, as you mentioned, function parameter pack has to be the last parameter unfortunately.
A non-template member function of a class template is an ordinary function for that class when it is instantiated(fully specialized). So I wish that the code in this question can be compiled logically, as a special case.