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jjant/cont_functor.hs

Last active August 7, 2018 21:15
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cont_functor.hs
{-# LANGUAGE InstanceSigs #-}
instance Functor (Cont r) where
fmap :: (a -> b) -> Cont r a -> Cont r b
-- Equivalent to
-- fmap :: (a -> b) -> ((a -> r) -> r) -> ((b -> r) -> r)
fmap f (Cont g) = Cont $ \k -> g (\a -> k (f a))
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