[C++-sig] Possible overload<> template for class members

[David Abrahams]

Aleksey Gurtovoy <agurtovoy at meta-comm.com> writes:

> Not in that exact form. Consider, for instance, this:
>
>     template< typename T > struct identity
>     {
>         typedef T type;
>     };
>
>     template< typename A0, typename R >
>     void
>     overload_cast(R (*f)(typename identity<A0>::type));
>
>     template< typename A0, typename A1, typename R >
>     void 
>     overload_cast( R (*f)( 
>           typename identity<A0>::type
>         , typename identity<A1>::type
>         ) );
>
>     bool show(int);
>     void show(int, bool);
>
>     int main()
>     {
>         overload_cast<int,bool>(&show); // ambiguous!
>     }
>
> Nasty, huh?

Yeah, OK.

We could do it with a class template that created a function object,
but I tend to doubt it's worth it.

   
> This one is always possible, of course:
>
>     void show();
>     bool show(int);
>     void show(int, bool*);
>     void show(int, bool);
>
>     struct window
>     {
>         void show();
>         bool show(int);
>         void show(int, bool*);
>         void show(int, bool);
>     };
>
>     int main()
>     {
>         overload(args<>(), &show);
>         overload(args<int>(), &show);
>         overload(args<int,bool*>(), &show);
>         overload(args<int,bool>(), &show);
>
>         overload(args<>(), &window::show);
>         overload(args<int>(), &window::show);
>         overload(args<int,bool*>(), &window::show);
>         overload(args<int,bool>(), &window::show);
>     }
>
> Or we can move the 'args' into function templates' template parameter list:
>
>         overload_cast< args<int,bool> >(&show);

That one seems like the nicest syntax I've seen so far.

-- 
                       David Abrahams
   dave at boost-consulting.com * http://www.boost-consulting.com
Boost support, enhancements, training, and commercial distribution