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EndoT #36

Open Gurkenglas opened 8 years ago

Gurkenglas commented 8 years ago 
import Data.Coercible
data EndoT m a = EndoT {runEndoT :: a  -> m a} deriving Wrapped

instance Monad m => Monoid (EndoT m a) where
  mempty = coerce return
  mappend = coerce (<=<)

(deriving Wrapped)