-- 021202
-- H98-compliant

module LiftMaybe(module Liftable) where

import Liftable

-- Make Maybe liftable

instance Liftable Maybe where
  lift0                     = Just
  lift1 f (Just x)          = Just (f x)
  lift1 f Nothing           = Nothing
  lift2 f (Just x) (Just y) = Just (f x y)
  lift2 f _         _       = Nothing