{-# htermination (maxChar :: Char -> Char -> Char) #-} import qualified Prelude data MyBool = MyTrue | MyFalse data List a = Cons a (List a) | Nil data Char = Char MyInt ; data MyInt = Pos Nat | Neg Nat ; data Nat = Succ Nat | Zero ; data Ordering = LT | EQ | GT ; 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; primCmpChar :: Char -> Char -> Ordering; primCmpChar (Char x) (Char y) = primCmpInt x y; compareChar :: Char -> Char -> Ordering compareChar = primCmpChar; 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); ltEsChar :: Char -> Char -> MyBool ltEsChar x y = fsEsOrdering (compareChar x y) GT; max0 x y MyTrue = x; otherwise :: MyBool; otherwise = MyTrue; max1 x y MyTrue = y; max1 x y MyFalse = max0 x y otherwise; max2 x y = max1 x y (ltEsChar x y); maxChar :: Char -> Char -> Char maxChar x y = max2 x y;