Kevin Atkinson, replying to me:
> > If I understand you correctly, then the best way of doing this would be
> > with existentially (boundedly) quantified data types, currently a
> > non-standard extention present in hbc (and I think, ghc, these days, not
> > sure if it's with the same generality.)
>
> existentially (boundedly) quantified data types can not cast up.
'Cast up' to what? If you can't write a class context that descibes
the relatedness of everything you want to put in a heterogenous collection,
then I'm inclined to doubt if it isn't more heterogenous than is
sensible.
> In order to do that you would ALSO need to use the dramatic typing
> extensions found in the GHC/Hugs library.
I don't see how this relates to anything other than heterogenous collections;
perhaps an example?
> The point that class hierarchy isn't precisely _type_ hierarchy is
> exactly the point I am trying to get gate Haskell needs to also be able to
> support a class hierarchy if it is to really support OO style programming.
I'm aware that Haskell doesn't precisely ape that sorts of 'OOP
style' that the likes of C++ admits What I've yet to see is any
argument that this is anything other than the wisest possible decision...
Cheers,
Alex.
