[Haskell-cafe] Instances of constrained datatypes
Marcin 'Qrczak' Kowalczyk
qrczak at knm.org.pl
Wed Apr 6 02:52:39 EDT 2005
Arjun Guha <guhaarju at grinnell.edu> writes:
> > data (Eq v) => EqList v = EqList [v]
> I'd like to make it an instance of Functor. However, fmap takes an
> arbitrary function of type a -> b. I need an Eq constraint on a and
> b. Is there any way to do this without creating my own `EqFunctor'
> class with explicitly-kinded quantification:
Why not to remove the Eq v constraint in the type?
__("< Marcin Kowalczyk
\__/ qrczak at knm.org.pl
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