ANNOUNCE: GHC 7.4.1 Release Candidate 1

Wolfgang Jeltsch g9ks157k at
Wed Dec 28 13:35:52 CET 2011

Am Donnerstag, den 22.12.2011, 00:02 +0100 schrieb Bas van Dijk:
> On 21 December 2011 19:29, Ian Lynagh <igloo at> wrote:
> >  * There is a new feature constraint kinds (-XConstraintKinds):
> >
> I'm trying to run the ConstraintKinds example from the documentation:
> {-# LANGUAGE ConstraintKinds, TypeFamilies #-}
> type family Typ a b :: Constraint
> type instance Typ Int  b = Show b
> type instance Typ Bool b = Num b
> But GHC complains:
>     Not in scope: type constructor or class `Constraint'

By the way, is there a reason behind the fact that “Constraint” uses the
ordinary case, while “BOX” has all three letters capitalized? Wouldn’t
it be more sensible if it were “Box” instead of “BOX”?

Things like capitalization might not seem very important first, but
unfortunately, decisions about them seem to persist.

Best wishes,

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