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From: David Abrahams (dave_at_[hidden])
Date: 2006-10-01 08:17:13

Jeremy Siek <jeremy.siek_at_[hidden]> writes:

> I also agree with Joel's position on airplanes (I misunderstood what
> he was saying at first... but yes, a pile of airplane parts is not
> an airplane), which is why I've always been in favor of explicit
> concept conformance. I see the concept_map declaration as the final
> touch that turns the parts into an airplane.

That isn't even enough in this case. One pair<int*,int*> object is
just a couple of pointers, while another is a sequence of ints.
Scoped concept_maps get us closer, but I'm not sure it's fully
general: you could still have both kinds of pair in the same code,

> I think the main thing to take away from this is that scoped
> concept maps are good. They allow you to have it both ways,
> in different parts of your program.
> And yes, we could solve the problem by requiring wrappers,
> but wrapping stuff is a pain.

Yep. There's too much of it already in C++.

Dave Abrahams
Boost Consulting

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