David Abrahams wrote:
"Brock Peabody" <brock.peabody@npcinternational.com> writes:
On Behalf Of Fernando Cacciola Sent: Tuesday, March 01, 2005 10:39 AM To: boost@lists.boost.org Subject: [boost] Re: [optional] new assignmet semantic and references
So I think I will fix it unless users speak up... Though I will post this issue in the users list as well.
First I'd like to say that I love optional<>. When I first read about it I didn't think I'd use it much, but now I find myself using it all over the place. It's useful for so many things, but to me the most important is how it improves my ability to make code self-documenting.
Personally, I like it the way it is. I've used optional quite a bit and it makes sense to me that operator= changes what an optional holds. I don't think it is a good idea to give operator= special semantics for references.
I had the same feeling. That's what I meant when I said
"It depends on whether you view optional<T> as a T that might just happen to be missing, or as a container for a T."
I think "a container for a T" is a more manageable meaning for optional<T>.
FWIW, a tuple<T&> can't be re-bound. I'll state my point again. I noticed this odd behavior of optional some years ago: giving optional re-binding semantics *is actually* giving it special semantics and requires special case handling. This leads to subtle problems like the one Fernando is experiencing now. If you want rebinding semantics, use a pointer, or use boost::ref. The right behavior, I strongly believe, is to do as the references do. This is what tuple did and we have nary a problem with it. Cheers, -- Joel de Guzman http://www.boost-consulting.com http://spirit.sf.net