"Powell, Gary" <powellg@amazon.com> wrote in message news:16D81990DBE42642A8CA977A55FF116A02D9F636@ex-mail-sea-02.ant.amazon.com...
This library is an interesting concept but when I looked in it, it didn't have what I would have thought were "container traits" the way I think of "iterator traits". From the VTL library I wanted to be able to query the container to see if it was an associative container, or a sequence container or a random access container, i.e. had an operator[]() etc.
Can one of the authors explain the purpose of this library?
Thorsten Ottosen is the authorative source on this point, but I think the library is mostly to provide support for algorithms which treat standard constainers, built-in arrays and iterator ranges uniformly. (I'm leaving out one case.) I, too, would like traits of the type you suggest, and I wish they would be added to the library. One problem, of course, is that theoretcially you could have a type which look like a container, because of its member types, but doesn't have the correct semantics. Also, the amount of introspection required to be reasonably sure you have a container has some compile-time cost. I think these problems are negligible if the traits are named and documented with these considerations in mind. Probably I've been reading the FC++ docs too much recently, but one might call them 'maybe_is_container', 'maybe_is_sequence', ... ;-) I think there should at least be traits for detecting standard container types (is_basic_string, is_vector, is_standard_sequence). One problem is that you might end up including the whole STL just to define these traits. Jonathan