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sjoerdvisscher/generic-unification.hs

Created June 20, 2017 12:47
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Generic unification with one-liner
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generic-unification.hs
-- See https://www.reddit.com/r/haskell/comments/6htj7z/generic_unification/
default zipMatch :: (ADT1 t, Constraints01 t Eq Unifiable) => t a -> t a -> Maybe (t (Either a (a, a)))
zipMatch = runZip $ generic01 @Eq @Unifiable
(Zip $ \a b -> if a == b then Just a else Nothing)
(\(Zip f) -> Zip $ \a b -> zipMatch a b >>= traverse (either (\x -> f x x) (uncurry f)))
(Zip $ \a b -> Just $ Right (a, b))
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