{-# htermination (lookup :: MyInt -> (List (Tup2 MyInt a)) -> Maybe a) #-} import qualified Prelude data MyBool = MyTrue | MyFalse data List a = Cons a (List a) | Nil data Tup2 a b = Tup2 a b ; data Maybe a = Nothing | Just a ; data MyInt = Pos Nat | Neg Nat ; data Nat = Succ Nat | Zero ; primEqNat :: Nat -> Nat -> MyBool; primEqNat Zero Zero = MyTrue; primEqNat Zero (Succ y) = MyFalse; primEqNat (Succ x) Zero = MyFalse; primEqNat (Succ x) (Succ y) = primEqNat x y; primEqInt :: MyInt -> MyInt -> MyBool; primEqInt (Pos (Succ x)) (Pos (Succ y)) = primEqNat x y; primEqInt (Neg (Succ x)) (Neg (Succ y)) = primEqNat x y; primEqInt (Pos Zero) (Neg Zero) = MyTrue; primEqInt (Neg Zero) (Pos Zero) = MyTrue; primEqInt (Neg Zero) (Neg Zero) = MyTrue; primEqInt (Pos Zero) (Pos Zero) = MyTrue; primEqInt vv vw = MyFalse; esEsMyInt :: MyInt -> MyInt -> MyBool esEsMyInt = primEqInt; lookup0 k x y xys MyTrue = lookup k xys; otherwise :: MyBool; otherwise = MyTrue; lookup1 k x y xys MyTrue = Just y; lookup1 k x y xys MyFalse = lookup0 k x y xys otherwise; lookup2 k (Cons (Tup2 x y) xys) = lookup1 k x y xys (esEsMyInt k x); lookup3 k Nil = Nothing; lookup3 wu wv = lookup2 wu wv; lookup k Nil = lookup3 k Nil; lookup k (Cons (Tup2 x y) xys) = lookup2 k (Cons (Tup2 x y) xys);