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akanehara/gist:5110329

Last active December 14, 2015 15:48
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gistfile1.hs
{-# LANGUAGE XNoMonomorphismRestriction #-}
import Control.Monad
newtype Foo m a b = Foo (m a -> (a -> m b))
instance (Monad m) => Monoid (Foo m a b) where
mempty = return
mappend x y = x <=< y
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