Re: template specialization

From:
Konstantin <klk206@panix.com>
Newsgroups:
comp.lang.c++
Date:
Sun, 14 Sep 2008 23:40:27 -0400
Message-ID:
<48CDD92B.7080707@panix.com>
mqrk wrote:

The simplest (and probably the best) solution is like this:


The problem still remains:

template <typename T> struct Container< T, std::set >
{
    std::set<T> data;
};

template <typename T> struct Container< T, std::list >
{
    std::list<T> data;
};

These are specializations, and one needs to write a primary template.
However, std::set template has three parameters: set<Key, Compare,
Alloc>, and std::list has only two: list<Type, Alloc>

Thus, if the primary template is

template < typename, template < typename, typename, typename > class >
    class Container;

then the second specialization yields an error ("error C3201: the
template parameter list for class template 'std::list' does not match
the template parameter list for template parameter ...")

and if the primary template is

template < typename T, template<typename, typename> class >
    class Container;

then the "set" template yields an error, and "list" works fine.

The same problem is in the solution with policies: the line
template <typename> class Container
in
template < typename T,
    template <typename> class Container,
    template <class > class AccessPolicy = DefaultAccessPolicy >
class MyContainer

will match neither std::set nor std::list for the same reason; adding
more arguments, e.g. template <typename,typename> class Container breaks
generality.

Is there a mechanism to reconcile these two? (E.g. something like
var-arg template arguments...)

Konstantin.

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