Re: [Haskell-cafe] type refinement to a typeclass constrained type

23 Mar 2007


      2007/3/23, Daniil Elovkov :
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Ok,
btw, this works :)
data Cnd c where
    In :: (Eq (c a)) => c a -> [c a] -> Cnd c
check :: (Eq (c a)) => Cnd c -> Bool
Eq constraint isn't even needed here, obviously
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check (x `In` items) = x `elem` items