In my design, - optional_poly<T> is default constructible and nullable - poly<T> is not default constructible and not nullable The difference between the two is mainly in constructors and assignment operator. I don't think we can have a generic nonnullable<Z> that can select and forward only the correct constructors. You have to specialize it for every pointer-like class, so it doesn't simplify the developer work, and imposes longer names (on average) on the users: optional_poly<T> becomes poly<T> (now nullable) poly<T> becomes nonnullable<poly<T> > (nonnullability is now explicit) Making non-nullability explicit, though, adds the benefit that generic interfaces can now explicitly request non-nullable arguments without knowing the exact type of what's passed inside (e.g. poly vs. shared_ptr). The same can be obtained in a design with different names by means of a trait (is_nullable< >), and using enable_if, but it seems clumsier. I'm fine with either approach. Corrado On 11/2/07, shunsuke <pstade.mb@gmail.com> wrote:
Corrado Zoccolo wrote:
Hi I've uploaded a new version of the library in the vault: * http://tinyurl.com/2og6st* It now provides also a new class (poly<T>) that maintains the never-empty guarantee. poly<T> and optional_poly<T> share a large part of their implementation, so I think it is sound to have both in the same library.
Hmm, it seems inherent that poly is DefaultConstructible(Nullable), IMHO.
Why not introduce `nonnullable`? nonnullable< poly<T> > nonnullable< boost::shared_ptr<T> >
BTW, poly<void> can't be "any"?
Regards,
-- Shunsuke Sogame
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-- __________________________________________________________________________ dott. Corrado Zoccolo mailto:zoccolo@di.unipi.it PhD - Department of Computer Science - University of Pisa, Italy -------------------------------------------------------------------------- The self-confidence of a warrior is not the self-confidence of the average man. The average man seeks certainty in the eyes of the onlooker and calls that self-confidence. The warrior seeks impeccability in his own eyes and calls that humbleness. Tales of Power - C. Castaneda