Status of Haskell'?

Roman Cheplyaka roma at
Tue Nov 27 18:24:55 CET 2012

* Brandon Allbery <allbery.b at> [2012-11-27 12:11:43-0500]
> On Tue, Nov 27, 2012 at 12:07 PM, Roman Cheplyaka <roma at> wrote:
> > > Maybe the question is whether we have anything.  We already skipped 2011
> > > because there wasn't anything worth the effort of a new standard.
> >
> > How about MultiParamTypeClasses, RankNTypes, ExistentialQuantification,
> >
> Do we have a definitive go/no-go on the FDs vs. TFs question yet?  I
> thought MPTC was not considered usable without one of those, and neither is
> yet considered standard (with some good reason in the case of FDs).

I see MPTCs and TFs as independent, in the sense that each one is usable
without the other. MPTCs allow the implementation to depend on multiple
types, while TFs allow the implementation *and* some other types to
depend on one type. Of course, in combination they are even more
powerful, allowing to have several "basis" types and several "dependent"

FDs are a bit different because they are not usable without MPTC.

Thus, FDs aside, MPTC usefulness should not depend on whether we accept

(FWIW, I agree with Edward that both FDs and TFs are very useful in


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