{-# htermination (succChar :: 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 ; primCharToInt :: Char -> MyInt; primCharToInt (Char x) = x; fromEnumChar :: Char -> MyInt fromEnumChar = primCharToInt; 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)); primPlusInt :: MyInt -> MyInt -> MyInt; primPlusInt (Pos x) (Neg y) = primMinusNat x y; primPlusInt (Neg x) (Pos y) = primMinusNat y x; primPlusInt (Neg x) (Neg y) = Neg (primPlusNat x y); primPlusInt (Pos x) (Pos y) = Pos (primPlusNat x y); psMyInt :: MyInt -> MyInt -> MyInt psMyInt = primPlusInt; pt :: (a -> c) -> (b -> a) -> b -> c; pt f g x = f (g x); primIntToChar :: MyInt -> Char; primIntToChar x = Char x; toEnumChar :: MyInt -> Char toEnumChar = primIntToChar; succChar :: Char -> Char succChar = pt toEnumChar (pt (psMyInt (Pos (Succ Zero))) fromEnumChar);