Jose Emilio Labra Gayo wrote:
> >
> > I agree; Haskell 2 should have existential (and universal) types. I
> > also think it should have both extensible records and extensible
> > variants. (See the following paper for more information on these.
> > TREX is an implementation of half of this system; it has the
> > extensible records but not extensible variants.)
> >
> > Carl Witty
> > [EMAIL PROTECTED]
> >
> Just a question, Is there anyone trying to implement extensible variants?
Johan Nordlander has developed a type system which allows subtyping on both
records and variants, at the same time as it stays very close in spirit to
the convetional Hindley/Milner types system. It is described in a ICFP'98
paper. You can get it from
http://www.cs.chalmers.se/~nordland/
There is also ongoing work on an implementation of a version of Haskell,
called OHaskell, which incoropates this type system.
--
Mvh Thomas H
