RE: [boost] Re: [mpl] Lambda problems (was: rebind<> bad;templat e template good)

From: Aleksey Gurtovoy (agurtovoy_at_[hidden])
Date: 2002-10-07 23:22:25

David B. Held wrote:
> I also see that my idea of making a 'metafunction
> base class' is not going to work as hoped.  I thought it 
> might be nice to have something like this:
> 
> template <class Policy>
> struct ownership_policy
> {
>     typedef typename Policy::type type; // Doesn't work
>     typedef ownership_policy_tag policy_category;
> };
> 
> template <typename T>
> struct ref_counted
>     : public ownership_policy<ref_counted<_>::type> // Bad
> {
>     // ...
> };

Hhm, how about this one:

    template< typename Policy >
    struct ownership_policy
    {
        typedef Policy type;
        typedef ownership_policy_tag policy_category;
    };

    template< typename T >
    struct ref_counted
        : ownership_policy< ref_counted<T> >
    {
        // ...
    };

?

Aleksey