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{-# LANGUAGE NoImplicitPrelude #-}
module Data.Functor where
import Data.Function
import Data.Tuple (fst, snd)
import Data.Maybe
class Functor f where
fmap :: (a -> b) -> f a -> f b
(<$) :: a -> f b -> f a
infixl 4 <$
(<$) = fmap . const
infixl 4 $>
($>) = flip (<$)
infixl 4 <$>
f <$> x = fmap f x
infixl 1 <&>
(<&>) = flip fmap
void x = () <$ x
unzip :: Functor f => f (a, b) -> (f a, f b)
unzip xs = (fst <$> xs, snd <$> xs)
instance Functor [] where
fmap f [] = []
fmap f (x:xs) = (f x):(fmap f xs)
instance Functor Maybe where
fmap f (Just x) = Just (f x)
fmap f Nothing = Nothing
instance Functor ((->) r) where
fmap = (.)
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