----- Original Message ----- From: "David Abrahams" <[EMAIL PROTECTED]>
> "Joel de Guzman" <[EMAIL PROTECTED]> writes: > > > ----- Original Message ----- > > From: "Fernando Cacciola" <[EMAIL PROTECTED]> > > > > > > > >> optional<> is trying to model using C++ a concept that > >> it is not really covered by the language, that of uninitialzed values. > >> It uses pointer semantics *just* because pointers are the only sort of > >> C++ objects which has a clear uninitialized state. > > > > Hi, > > > > Probably a dumb question but allow me to ask anyway: > > > > Wouldn't a more generic variant<T0, T1...TN> class do what the > > optional is trying to do? I feel that optional<T> is just a variant<T, nil_t> > > in disguise. Correct me if I'm wrong. > > Someone once said that if a theorem in Physics involves numbers other > than zero, 1, or infinity, it's lacking in purity. :-) Cool! > optional captures the zero/one distinction, which, as its analogy to > pointers makes clear, is a very useful one. A type which can contain > any number of different types would have a much more complicated > interface. Maybe it's just a different library? Or perhaps, optional is just a limited add-on API over the variant? The low-level implementation mechanism in place seems to be very similar and having 2 separate libraries will be redundant, I think. Joel de Guzman [EMAIL PROTECTED] http://www.boost-consulting.com _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
