Re: How to fix DatatypeContexts?

I'd use GADT syntax for this: {-# LANGUAGE GADTs #-} data Pair a where Pair :: Eq a => {x::a, y::a} -> Pair a Sjoerd On Jul 18, 2013, at 1:05 PM, Christopher Done wrote:

Hm, also, with equality constraints you can make the type parametrized, too:

data Pair a' = forall a. (a ~ a', Eq a) => Pair {x::a, y::a} equal :: Pair a -> Bool equal (Pair x y) = x == y

On 18 July 2013 13:00, Christopher Done wrote: Why not this?

data Pair = forall a. Eq a => Pair {x::a, y::a} equal :: Pair -> Bool equal (Pair x y) = x == y

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