[boost] Re: Partially specializing less<> with nested template class

From: Jonathan Turkanis (technews_at_[hidden])
Date: 2004-07-08 16:26:37

"David B. Held" <dheld_at_[hidden]> wrote in message
news:cck1t5$g3r$1_at_sea.gmane.org...
> This is what I would like to do:
>
> template <class P1, class P2>
> struct sp
> {
>      template <typename T>
>      struct nested { };
> };
>
> template <typename T>
> struct less;
>
> template <class P1, class P2, typename T>
> struct less<sp<P1, P2>::nested<T> >
>      : binary_function<...>
> {
>      bool operator()(...);
> };
>

Could you pull the definition of nested outside of sp

    template<typename P1, typename P2, typename T>
    struct sp_nested { };

then use a metafunction within sp:

    template<typename P1, typename P2>
    struct sp {
         template<typename T>
         struct nested {
             typedef sp_nested<P1, P2, T> type;
         };
    };

?

You can then make less< sp_nested<P1, P2, T> > do pretty much whatever
you want; the question is whether you can make the metafunction do
whatever you needed the nested template to do.

Jonathan