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Improved semigroups
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import Data.Semigroup | |
data Improve a = Improve (a -> a) a | |
instance Semigroup (Improve a) where | |
~(Improve a' a) <> ~(Improve b' b) = Improve (a' . b') (a' b) | |
improve :: Semigroup a => a -> Improve a | |
improve a = Improve (a <>) a | |
disprove :: Improve a -> a | |
disprove ~(Improve _ a) = a | |
-- | |
infixr 6 :<> | |
data M a = M a | M a :<> M a | |
deriving Show | |
instance Semigroup (M a) where | |
(<>) = (:<>) | |
m :: a -> Improve (M a) | |
m = improve . M | |
-- >>> disprove $ ((m 1 <> m 2) <> m 3) | |
-- M 1 :<> (M 2 :<> M 3) | |
-- | |
-- >>> disprove $ fix ((m 1 <> m 2) <>) | |
-- M 1 :<> (M 2 :<> (M 1 :<> (M 2 :<> (... |
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