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Created April 2, 2021 22:05
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instance.hs
instance Functor Maybe where
fmap :: (a -> b) -> Maybe a -> Maybe b
fmap (_ :: a -> b) (Nothing :: Maybe a) = Nothing :: Maybe b
fmap (f :: a -> b) (Just x :: Maybe a) = Just ((f :: a -> b) (x :: a) :: b) :: Maybe b
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