-- 021202
-- H98-compliant

-- Liftable is essentially an extension of Functor. fmap and lift1 should be
-- the same. We could have opted to make Liftable a subclass to Functor, but
-- haven't done so. If some good reason appears, then we might revert this
-- decision.

module Liftable where

class Liftable k where
  lift0 :: a -> k a
  lift1 :: (a -> b) -> (k a -> k b)
  lift2 :: (a -> b -> c) -> (k a -> k b -> k c)