Joao Abecasis <jpabecasis@zmail.pt> writes:
David Abrahams wrote:
I think the question is whether it's ever desirable to break the current C++ invariant that no two objects of the same type will ever share an address **in generic code** -- that is, when you don't know anything about the assumptions that may be made by that type.
An alternative implementation is to privately inherit from the specified type for empty classes as compressed_pair does. This maintains the invariant but has the drawback that inheritance is visible in user code.
Yeah, the primary danger being unintentional overriding of virtual functions from the private base. I like the protection your idea provides. You could arrange a compressed_pair based on this design that still maintains the invariant. And then you could make it smart enough to aggregate other compressed_pairs without ever allocating two of the same type at the same address.
For a generic compressed_tuple the private inheritance should not be a problem.
I'm not sure what you mean by that, sorry. -- Dave Abrahams Boost Consulting http://www.boost-consulting.com