data Boolean = Wahr | Falsch deriving Show
data Paar a = Paar a a deriving Show
data Liste a = Nil | Cons a (Liste a) deriving Show
data GeomObjekt = Linie (Paar Int) Int
                | Rechteck  (Paar Int) Int Int
                | Quadrat  (Paar Int) Int
  deriving Show

und     :: Boolean -> Boolean -> Boolean
und a b = case a of
  Wahr -> b
  Falsch -> Falsch

operationPaar :: (a -> a -> b) -> Paar a -> b
operationPaar f (Paar a b) = f a b

undPaar   :: Paar Boolean -> Boolean
undPaar p = operationPaar (\ a b -> und a b) p

--mapListe     :: 
mapListe f l =  undefined

--undPaarListe   :: 
undPaarListe l =  undefined

--istQuadrat   :: 
istQuadrat l =  undefined