Tom Pledger writes:
> [...]
>
> --Subtype should be transitive; I may have done something evil
> --here, because Classic Hugs (November 1999) with the `-98' flag
> --rejects this decl with the message `Undefined type variable "b"'
> instance (Subtype a b, Subtype b c) => Sub
Keith Wansbrough writes:
> > class Subtype sub super where
> > up :: sub -> super
> > down :: super -> Maybe sub
>
> See the extensible union types of [Sheng Liang, Paul Hudak and Mark
> Jones: Monad Transformers and Modular Interpreters]
>
> From the abstract:
>
> class Subtype sub super where
> up :: sub -> super
> down :: super -> Maybe sub
See the extensible union types of
@InProceedings{
Liang*95:Monad,
author="Sheng Liang and Paul Hudak and Mark Jones",
title="Monad Transformers and Modular Interpreters",
crossre
The recent suggestion that OO and FP are somewhat out of phase reminds
me of a pet topic: overlapping types. This is (IMHO) the only feature
of OO for which there is (AFAICS) no FP equivalent.
Here's a more concrete proposal than my previous vague rants on the
subject.
module Treat
