data Data0 = Data0

data Data1 a b c = Data1 a b c

data Data2 = Data21 Int
           | Data22 { x :: Int, y::Int }
           | Data23 { x :: Int }
           | Data24 { }

data Data5 a5 b5 c5 = Data51 { a5::a5}
                    | Data52 { a5::a5, b5::b5, c5::c5 }
                    | Data53 Int a5 Float b5 c5

{-
f (Data41 {}) = 5
f (Data42 {c4=c}) = c
f d = a4 d
-}