Re: [Boost-users] [multi-index] member arguments [Was: how to use in heritmember as index]

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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 struct member;

#define MEMBER(PtrToMember) \ member

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 struct get_pointer_to_member_details { 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