Peter Dimov wrote:
Joel de Guzman wrote:
Oh, I forgot: http://boost.org/libs/optional/doc/optional.html#refassign
To this day, I'm still befuddled at the explanation.
What's wrong with it?
"Rebinding semantics for the assignment of initialized optional references has been chosen to provide consistency among initialization states..."
There's nothing wrong with that. That's clear. You've snipped out the other parts though. What's not clear is why code like that posted by AlisdairM should assume the behavior: http://lists.boost.org/Archives/boost/2005/10/95487.php A gotcha AFAICT.
seems pretty clear to me. Since assignment to an uninitialized optional<T&> rebinds, so does assignment to initialized optional<>.
Consider the analogy with variant<T&, U&>. What does assignment do? Under the "always rebind" model it rebinds. Under the "behave as a reference" model it depends on the argument type and the current state of the variant. It may assign to the referenced object, or it may rebind.
No. Under the "behave as a reference" model, references should bind only on construction. Everything else is assignment to the referenced object. No rebind.
"Always rebind" certainly appears more consistent to the untrained eye.
Really? To me this is definiteley wrong no matter how you put it: int a = 13; int &b = a; int c = 42; optional< int & > d = b; d = c; // rebind! Ok, this is definitely my last post on the issue. Cheers! -- Joel de Guzman http://www.boost-consulting.com http://spirit.sf.net