David Abrahams wrote:
Joel de Guzman <joel@boost-consulting.com> writes:
Rebinding semantics are there _precisely_ and _only_ to solve a problem posed by nullability.
Sorry, I don't buy that.
Why not?
I think this is again an artifact of the confusion between the dual interfaces that optional provides. optional has an identity crisis of being a pointer (as the author's original model) and a variant<T, nil> (which I suggested later on). The rebinding behavior that Fernando rationalized was long and winding and confusing. I don't recall anymore his exact rationale. All I know is that when you have to explain your design using so much wordings, then something is wrong, and I don't buy the gobbledegook. There *is* an alternative design which is a lot simpler and I've been saying that again and again: do as the structs do. It is easier to visualize and understand and ultimately to explain. A more complex design and behavior will surely lead to more gotchas. Keep it as simple as possible. variant<T&, nil> does the right thing. I don't understand why optional can't. Perhaps it's because of the dual pointer interface. But, like Mat Marcus, I also don't buy the pointer model: "Pointers can be null or dereference-able, Optionals can be null or dereferenceable, therefore Optionals are models of Pointers". It seems that Fernando's rationale follows along the lines "Pointers can be null or dereference-able, Optionals can be null or dereferenceable, Pointers can be rebound, therefore Optionals should be rebound-able." Sorry, that does not work for me. Regards, -- Joel de Guzman http://www.boost-consulting.com http://spirit.sf.net