I'm just curious - is there a reason why "member" takes 3 template parameters, and not just one, like in
member<&Peer::userid>
? The first two types can be extracted from the member pointer, so I find this a bit redundant...
It certainly looks redundant, but it turns out you really cannot do what you propose:
template<...> struct member;
What should "..." look like? It's not a type parameter, but it cannot be made a non-type parameter either since we don't know the type of the pointer-to-member being passed...
In decltype- (or typeof-) enabled compilers a terser syntax could be achieved by using some macro hackery:
template<typename PtrToMemberType,PtrToMemberType PtrToMember> struct member;
#define MEMBER(PtrToMember) \ member<decltype(PtrToMember),PtrToMember>
So maybe when C++0x arrives we can take advantage of this.
I use this template in my code: template<typename T> struct get_pointer_to_member_details; template<typename Class, typename Member> struct get_pointer_to_member_details<Member Class::*> { typedef Class class_type; typedef Member member_type; }; Using this, you can write (and I do) something like template<typename MemberPointerType> struct member { MemberPointerType pMember; typedef typename get_pointer_to_member_details<MemberPointerType>::class_type class_type; typedef typename get_pointer_to_member_details<MemberPointerType>::member_type result_type; member(MemberPointerType pMember) : pMember(pMember) {} // ... } I wonder then, is it MSVC 8 that allows something non-standard, or is it OK? I think I tried with recent gcc as well and it worked... Cheers, Filip