[Haskell-cafe] Type extensions

[ajb at spamcop.net]

G'day all.

Quoting Thomas Davie <tom.davie at gmail.com>:

> Essentially I would like some sort of inderritance property for
> Haskell types, I often find myself wanting to for example extend a
> tree with black/white colouring, or later extend the tree with some
> sort of ID, etc.

Have you had a look at these?

        http://haskell.org/hawiki?IndirectComposite
        http://haskell.org/hawiki?DecoratingStructures

Cheers,
Andrew Bromage