From: Fernando Cacciola (fernando_cacciola_at_[hidden])
Date: 2006-10-06 11:00:27
Vaclav Vesely wrote:
> Hi,
>
> I would like to do somethink like this:
>
> class Base {...}
> class Derived: public Base {...}
>
> optional<Base> x = Derived();
> y->call_virtual_functions()
>
> Current design of boost::optional doesn'g support this. But I wonder if it's
> to possible to extend it.
>
> I created simple prototype to verify the technique (see attachment). It
> works this way:
>
> optional<BaseT>
> - has attribut _value_holder of type value_holder<BaseT>*
> - _value_holder points to the instance of derived_value_holder<BaseT,
> DerivedT>, where DerivedT is the type of stored value
>
It looks a lot like Boost.Any.
Have you looked at it?
Fernando Cacciola
SciSoft
http://fcacciola.50webs.com