replicateEndo.hs

import Data.Foldable (fold)
import Data.Monoid (Endo(Endo, appEndo))

-- | @replicateEndo n f@ replicates n times an endomorphism f and folds them using
-- function composition to an endomorphism @a -> a@.
-- 
-- Propositions:
-- > replicateEndo _ id == id
-- > replicateEndo _ (const x) == const x
-- > replicateEndo 0 _ == id
replicateEndo :: Int -> (a -> a) -> a -> a
replicateEndo n = appEndo.fold.replicate n.Endo