On Sun, 04 Sep 2011 00:56:50 -0700, Nevin Liber <nevin@eviloverlord.com> wrote:
On 4 September 2011 00:14, Mostafa <mostafa_working_away@yahoo.com> wrote:
That seems to be the consensus so far. Assuming that I'm creating optional2, so we don't have to worry about existing code, and that it's equivalent to optional in all respects except that the assignment operator has now been disallowed across the board, and we've only retained a no-argument reset method. What are the implications of that?
The same problem that references and const variables have; namely, any class that has them as members is non-Assignable (both non-CopyAssignable and non-MoveAssignable).
Ok, that's a valid concern. I forgot to generalize the implication to the composing class.
That leaves using your class for local variables or parameters, and I don't see much usefulness there either, as a pointer is a far easier construct to use for such a localized effect.
I'm going to go off-topic here, but it's going to explain my reasons for considering the use of optional. The problem with using pointers/references to represent the "is optional"/"is required" idiom is two-fold: 1) Raw Pointers Raw pointers don't convey the semantics of their life-time policy, hence one has to rely on some convention, which can easily change from project to project even within the same company. Hence the motivation for using smart pointers where feasible. 2) Smart Pointers Smart pointers are nice in that they convey the semantics of their life-time, but their have been many discussions on this forum which have advised against passing or returning a dereferenced smart pointer by reference. If we were to follow the latter advice, and I am inclined to do so, then smart pointers become a noop for the aforementioned idiom. And this creates a new problem, in that now smart pointers don't convey the semantics of their "optionalness". Which brings me to Boost.Optional. Boost.Optional is nice because it conveys its intent explicitly, and I can use it directly with smart pointers. Mostafa