Ord instance for Data.Map?

Bertram Felgenhauer bertram.felgenhauer at googlemail.com
Tue Apr 17 08:16:53 EDT 2007

Henning Thielemann wrote:
> > > instance Ord x => Ord (Index (Complex x)) where
> > >    (Index (Complex a b)) `compare` (Index (Complex c d)) =
> > >        (a, b) `compare` (c, d)
> >
> > should be good enough. 'Index' marks the purpose for the type.
> That requires extended instance declarations, doesn't it?

Aha. Yes it does. I don't see any simpler workaround than the one
you proposed then, while sticking to Haskell 98.



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