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chessai/cool.hs

Last active November 13, 2018 21:13
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cool.hs
import Data.Functor.Compose
doubleFmap :: (Functor f, Functor g) => (a -> b) -> f (g a) -> f (g b)
doubleFmap = fmap . fmap
fooMonad :: (Monad f, Functor g) => f (a -> b) -> f (g a) -> f (g b)
fooMonad fab fga = fab >>= \f -> doubleFmap f fga
fooApplicative :: (Applicative f, Applicative g) => f (a -> b) -> f (g a) -> f (g b)
fooApplicative fab fga = getCompose (Compose (fmap pure fab) <*> Compose fga)
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