From: Itay Maman (itay_maman_at_[hidden])
Date: 2002-06-13 18:54:18
I'd like to address some issues:
1. should all types be different?
Seems like a reasonable requirement
2. Is direct recursion (i.e: variant<int, rec>) allowed?
I think we should not allow instantiations like this:
variant<int, rec> v1;
Doug has made some serious points against conversion policies. I do
agree with him. Anyway, variant's user will always be able to get whatever
conversion effect he needs by writing a suitable visitor.
As for the storage policy, I do find it is useful (to the same extent as
allocators...) but I am willing to drop that as well on practical
It will only be used in extremely rare cases. (2) Combining a default
parameter with a non type-list interface will (unjustifably) complicate
variant's Instantiation interface.
The conversion behavior should use overload resolution rules.
4. Instantiation interface
We should support both options, i.e:
typename T1, typename T2 = Unused_tag, typename, T3 =
- and -
template<typename H, typename T>
class variant<TypeList<H,T> >;
In either option, variant's internal implementation should be
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