[Haskell-cafe] Re: Small displeasure with associated type synonyms
Tom Schrijvers
Tom.Schrijvers at cs.kuleuven.be
Fri Mar 7 02:07:57 EST 2008
> Am I correct in thinking this would have worked if it were an
> associated type instead of an associated type synonym?
>
> ie,
>
> class C a where
> data T a
> val :: T a
Yes, you are. Associate data type constructors (as well as ordinary
algebraic data constructors) are injective. So we have:
forall a b . T a = T b <=> a = b
Cheers,
Tom
--
Tom Schrijvers
Department of Computer Science
K.U. Leuven
Celestijnenlaan 200A
B-3001 Heverlee
Belgium
tel: +32 16 327544
e-mail: tom.schrijvers at cs.kuleuven.be
url: http://www.cs.kuleuven.be/~toms/
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