# module Data.Maybe (  
#     Maybe(Nothing, Just),  maybe,  isJust,  isNothing,  fromJust,  fromMaybe,  
#     listToMaybe,  maybeToList,  catMaybes,  mapMaybe  
#   ) where instance Monad Functor MonadPlus Eq Ord Read Show
# maybe
nothing = \ j n . n
just = \ a j n . j a
maybe = \ b ab m . m ab b