{-# htermination (drop :: MyInt -> (List a) -> (List a)) #-} import qualified Prelude data MyBool = MyTrue | MyFalse data List a = Cons a (List a) | Nil data MyInt = Pos Nat | Neg Nat ; data Nat = Succ Nat | Zero ; data Ordering = LT | EQ | GT ; primMinusNat :: Nat -> Nat -> MyInt; primMinusNat Zero Zero = Pos Zero; primMinusNat Zero (Succ y) = Neg (Succ y); primMinusNat (Succ x) Zero = Pos (Succ x); primMinusNat (Succ x) (Succ y) = primMinusNat x y; primPlusNat :: Nat -> Nat -> Nat; primPlusNat Zero Zero = Zero; primPlusNat Zero (Succ y) = Succ y; primPlusNat (Succ x) Zero = Succ x; primPlusNat (Succ x) (Succ y) = Succ (Succ (primPlusNat x y)); primMinusInt :: MyInt -> MyInt -> MyInt; primMinusInt (Pos x) (Neg y) = Pos (primPlusNat x y); primMinusInt (Neg x) (Pos y) = Neg (primPlusNat x y); primMinusInt (Neg x) (Neg y) = primMinusNat y x; primMinusInt (Pos x) (Pos y) = primMinusNat x y; msMyInt :: MyInt -> MyInt -> MyInt msMyInt = primMinusInt; drop0 n (Cons vw xs) = drop (msMyInt n (Pos (Succ Zero))) xs; drop1 vv Nil = Nil; drop1 vz wu = drop0 vz wu; drop2 n xs MyTrue = xs; drop2 n xs MyFalse = drop1 n xs; primCmpNat :: Nat -> Nat -> Ordering; primCmpNat Zero Zero = EQ; primCmpNat Zero (Succ y) = LT; primCmpNat (Succ x) Zero = GT; primCmpNat (Succ x) (Succ y) = primCmpNat x y; primCmpInt :: MyInt -> MyInt -> Ordering; primCmpInt (Pos Zero) (Pos Zero) = EQ; primCmpInt (Pos Zero) (Neg Zero) = EQ; primCmpInt (Neg Zero) (Pos Zero) = EQ; primCmpInt (Neg Zero) (Neg Zero) = EQ; primCmpInt (Pos x) (Pos y) = primCmpNat x y; primCmpInt (Pos x) (Neg y) = GT; primCmpInt (Neg x) (Pos y) = LT; primCmpInt (Neg x) (Neg y) = primCmpNat y x; compareMyInt :: MyInt -> MyInt -> Ordering compareMyInt = primCmpInt; esEsOrdering :: Ordering -> Ordering -> MyBool esEsOrdering LT LT = MyTrue; esEsOrdering LT EQ = MyFalse; esEsOrdering LT GT = MyFalse; esEsOrdering EQ LT = MyFalse; esEsOrdering EQ EQ = MyTrue; esEsOrdering EQ GT = MyFalse; esEsOrdering GT LT = MyFalse; esEsOrdering GT EQ = MyFalse; esEsOrdering GT GT = MyTrue; not :: MyBool -> MyBool; not MyTrue = MyFalse; not MyFalse = MyTrue; fsEsOrdering :: Ordering -> Ordering -> MyBool fsEsOrdering x y = not (esEsOrdering x y); ltEsMyInt :: MyInt -> MyInt -> MyBool ltEsMyInt x y = fsEsOrdering (compareMyInt x y) GT; drop3 n xs = drop2 n xs (ltEsMyInt n (Pos Zero)); drop3 wv ww = drop1 wv ww; drop :: MyInt -> (List a) -> (List a); drop n xs = drop3 n xs; drop vv Nil = drop1 vv Nil; drop n (Cons vw xs) = drop0 n (Cons vw xs);