content: {-# LANGUAGE DeriveDataTypeable #-}
  
  import Data.Generics
  
  import Data.Binary
  
  import BinaryDerive
  
  data Foo = Bar
      deriving (Typeable, Data, Show, Eq)
  
  instance Binary Main.Foo where
    put Bar = return ()
    get = return Bar
  
  data Color = RGB Int Int Int
             | CMYK Int Int Int Int
      deriving (Typeable, Data, Show, Eq)
  
  instance Binary Main.Color where
    put (RGB a b c) = putWord8 0 >> put a >> put b >> put c
    put (CMYK a b c d) = putWord8 1 >> put a >> put b >> put c >> put d
    get = do
      tag_ <- getWord8
      case tag_ of
        0 -> get >>= \a -> get >>= \b -> get >>= \c -> return (RGB a b c)
        1 -> get >>= \a -> get >>= \b -> get >>= \c -> get >>= \d -> return (CMYK a b c d)
  
  data Computer = Laptop { weight :: Int }
                | Desktop { speed :: Int, memory :: Int }
      deriving (Typeable, Data, Show, Eq)
  
  instance Binary Main.Computer where
    put (Laptop a) = putWord8 0 >> put a
    put (Desktop a b) = putWord8 1 >> put a >> put b
    get = do
      tag_ <- getWord8
      case tag_ of
        0 -> get >>= \a -> return (Laptop a)
        1 -> get >>= \a -> get >>= \b -> return (Desktop a b)
  
  data Exp = ExpOr Exp Exp
           | ExpAnd Exp Exp
           | ExpEq Exp Exp
           | ExpNEq Exp Exp
           | ExpAdd Exp Exp
           | ExpSub Exp Exp
           | ExpVar String
           | ExpInt Int
      deriving (Typeable, Data, Show, Eq)
  
  instance Binary Main.Exp where
    put (ExpOr a b) = putWord8 0 >> put a >> put b
    put (ExpAnd a b) = putWord8 1 >> put a >> put b
    put (ExpEq a b) = putWord8 2 >> put a >> put b
    put (ExpNEq a b) = putWord8 3 >> put a >> put b
    put (ExpAdd a b) = putWord8 4 >> put a >> put b
    put (ExpSub a b) = putWord8 5 >> put a >> put b
    put (ExpVar a) = putWord8 6 >> put a
    put (ExpInt a) = putWord8 7 >> put a
    get = do
      tag_ <- getWord8
      case tag_ of
        0 -> get >>= \a -> get >>= \b -> return (ExpOr a b)
        1 -> get >>= \a -> get >>= \b -> return (ExpAnd a b)
        2 -> get >>= \a -> get >>= \b -> return (ExpEq a b)
        3 -> get >>= \a -> get >>= \b -> return (ExpNEq a b)
        4 -> get >>= \a -> get >>= \b -> return (ExpAdd a b)
        5 -> get >>= \a -> get >>= \b -> return (ExpSub a b)
        6 -> get >>= \a -> return (ExpVar a)
        7 -> get >>= \a -> return (ExpInt a)
        _ -> fail "no decoding"
  