[Haskell-cafe] Class Synonyms - example 2
Jorge Adriano Aires
jadrian at mat.uc.pt
Sat Dec 11 12:56:25 EST 2004
> > Besides the case where 'a' is the same as 'b', there is also another
> > interesting case. That is when you have both, Foo A B and Foo B A.
> > This is a
> > known property (named DoubleFoo) [...]
> Again, with -fallow-undecidable-instances:
> class (Foo a b, Foo b a) => DoubleFoo a b
> instance (Foo a b, Foo b a) => DoubleFoo a b
Ah! Got it.
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