Hi again,
Fernando Cacciola wrote:
That is, we can't just yet write that as: template<class T, class U> bool optional_assign( T&, optional<U>&& ) ; as we would a few years from now.
Well, we can achieve almost the same in old C++03, by declaring the function as a /member/ of optional<T>. I'd suggest naming it "optional_move_to", as follows:
On further thinking, if the optional is an lvalue this would do the right thing but will have the wrong name o) So, we need "optional_copy_to()" if we want users to explicitely choose between move vs copy. Or, probably better, a single [optional_]assign_to() that magically does one or the other depending on "this" being and lvalue or rvalue reference Something which, btw, in C++0x can actually be properly overloaded: template<class U> bool optional<T>::assign_to( U& ) & ; template<class U> bool optional<T>::assign_to( U& ) && ; This is getting unsurprisingly closer to the initial proposal from Arno :) The main difference being the usage of a member function instead in order to leverage move optimizations in current C++. Cheers -- Fernando Cacciola SciSoft Consulting http://www.scisoft-consulting.com