{-# LANGUAGE MultiParamTypeClasses, FlexibleInstances, CPP #-}
import Data.Time

#define as ::

class Cast a c where
  cast :: a -> c

instance Show a => Cast a [Char] where
  cast = show

instance Cast UTCTime Day where
  cast = utctDay

main = do
    now <- getCurrentTime
    print (cast now as String)
    print (cast now as Day)
    print (cast (cast now as Day) as String)