"Eric Friedman" <[EMAIL PROTECTED]> wrote in message b2s34c$bav$[EMAIL PROTECTED]">news:b2s34c$bav$[EMAIL PROTECTED]... > Fernando Cacciola wrote: > [snip] > > (3) variant<> dependency. > > > > We are just about to review boost::variant<>. > > I was planning to wrap optional<> around variant discarding its current > > implementation. > > This might seem like a good idea in theory, but for the simple case > presented by optional<>, the baggage of variant's implementation is overkill > IMO. > Indeed. I've been looking at the implementation and it is exactly the case. Anyway, I see that you're progressing towards move semantics, so I will likely find useful those utilities once you finish them (in order to increase exception guarantess)
> > It might be useful in the future, however, to build a tests for optional > that compares your boost::optional<T> against a suitably-wrapped > boost::variant<empty, T>. > Yes. > > However, to support the in-place form and use variant<>, the later will > have > > to suppport this form itself. > > > > Proposed solution: > [snip] > > ...I figured that a factory could move the forwarding problem out of > > optional<> > > while at the same time allow for an almost identical usage. > > This seems like a good idea, particularly in terms of integrating > factory-based initialization with variant. > Great. > [snip] > > It allows to use in-place for noncopyable default-constructible objects: > > > > optional<Z> opt(true,in_place()); > > > > It allows you to have alternative factories which support alternative > > forwarding methods: > > > > optional<X> opt(false,in_place2(2,"hello")); > > > > And since the factory can be reused, plugging the mechanism into > variant<>, > > for instance, is trivial. > > > > Notice that the verbosity is actually put in the in-place factory mainly. > > I would implement and document such factory as another utility and just > > use it on optional<> interface. > > Let me know when you get this working for optional<>. I personally would be > quite interested in seeing how it might fit into variant<>. (I won't be > making any changes, however, until after variant's review has ended.) > OK. I'll keep you inform. -- Fernando Cacciola _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
