Re: [Haskell-cafe] Type equality proof

[Martijn van Steenbergen]

Martijn van Steenbergen wrote:

class Eq2 f where
  eq2 :: f a b -> f a' b' -> Maybe (a :=: a', b :=: b')

Is that right, or does the following make more sense?

class Eq2 f where
  eq2 :: f a b -> f a' b' -> (Maybe (a :=: a'), Maybe (b :=: b'))

Thanks,

Martijn.

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