About Free Monad

Free Monad

Free monad allows us to construct a monad from a functor:

1	data Free f r = Free (f (Free f r)) \| Pure r

instance (Functor f) => Monad (Free f) where
  return = Pure
  Pure a >>= k = k a
  Free m >>= k = Free ((>>= k) <$> m)

Free Monad gives you a free monad for a given functor.