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{-# LANGUAGE DefaultSignatures #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE TypeFamilies #-}
module T11608 where
type Traversal s t a b = forall f. Applicative f => (a -> f b) -> s -> f t
class Each s t a b | s -> a, t -> b, s b -> t, t a -> s where
each :: Traversal s t a b
default each :: (Traversable g, s ~ g a, t ~ g b) => Traversal s t a b
each = traverse
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