"Calum Grant" <calum@visula.org> writes:
I've been following this dual_state vs optional discussion for a while. It seems to me that one should really have a policy class that defines the default behaviour when the value is unassigned. This policy should define whether to
- throw an exception - construct an object on the fly - return a default - return a null pointer - whether to return by value or by reference
A second point, can't all this be achieved by adding policies to smart pointers?
Whoa; smart pointers and boost::optional are not very closely related beasts. If you add enough policies to std::list you could probably handle this use case, too. I don't think finding something to policy-ize is always the best way to fit new designs into an existing framework. -- Dave Abrahams Boost Consulting www.boost-consulting.com