[Haskell] Announce: ~Haskell 2011
Malcolm Wallace
malcolm.wallace at me.com
Thu Jan 20 14:26:37 CET 2011
>> (a) we wish to accept the NoDatatypeContexts proposal
>> http://hackage.haskell.org/trac/haskell-prime/wiki/NoDatatypeContexts
>
> The Trac-Wiki says: "What removing the datatype contexts from a source
> file will do is make some previously illegal programs legal." What
> is an
> example?
As on the wiki,
data Eq a => Foo a = Constr a
getVal :: Foo a -> a
getVal (Constr x) = x
would previously have been rejected. Once the compiler forces the
user to remove the Eq a => context on the datatype, the rest of the
program will be accepted.
Regards,
Malcolm
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