{-# LANGUAGE NoImplicitPrelude #-} module Number.ResidueClass.Func where import qualified Number.ResidueClass as Res import qualified Algebra.PrincipalIdealDomain as PID import qualified Algebra.IntegralDomain as Integral import qualified Algebra.Field as Field import qualified Algebra.Ring as Ring import qualified Algebra.Additive as Additive import PreludeBase import NumericPrelude hiding (zero, one, ) import qualified Prelude as P import qualified NumericPrelude as NP {- | Here a residue class is a representative and the modulus is an argument. You cannot show a value of type 'T', you can only show it with respect to a concrete modulus. Values cannot be compared, because the comparison result depends on the modulus. -} newtype T a = Cons (a -> a) concrete :: a -> T a -> a concrete m (Cons r) = r m fromRepresentative :: (Integral.C a) => a -> T a fromRepresentative = Cons . mod lift0 :: (a -> a) -> T a lift0 = Cons lift1 :: (a -> a -> a) -> T a -> T a lift1 f (Cons x) = Cons \$ \m -> f m (x m) lift2 :: (a -> a -> a -> a) -> T a -> T a -> T a lift2 f (Cons x) (Cons y) = Cons \$ \m -> f m (x m) (y m) zero :: (Additive.C a) => T a zero = Cons \$ const Additive.zero one :: (Ring.C a) => T a one = Cons \$ const NP.one fromInteger :: (Integral.C a) => Integer -> T a fromInteger = fromRepresentative . NP.fromInteger equal :: Eq a => a -> T a -> T a -> Bool equal m (Cons x) (Cons y) = x m == y m instance (Integral.C a) => Additive.C (T a) where zero = zero (+) = lift2 Res.add (-) = lift2 Res.sub negate = lift1 Res.neg instance (Integral.C a) => Ring.C (T a) where one = one (*) = lift2 Res.mul fromInteger = Number.ResidueClass.Func.fromInteger instance (PID.C a) => Field.C (T a) where (/) = lift2 Res.divide recip = (NP.one /) fromRational' = error "no conversion from rational to residue class" {- NumericPrelude.fromInteger seems to be not available at GHCi's prompt sometimes. But Prelude.fromInteger requires Prelude.Num instance. -} -- legacy instances for work with GHCi legacyInstance :: a legacyInstance = error "legacy Ring.C instance for simple input of numeric literals" instance (P.Num a, Integral.C a) => P.Num (T a) where fromInteger = Number.ResidueClass.Func.fromInteger negate = negate --for unary minus (+) = legacyInstance (*) = legacyInstance abs = legacyInstance signum = legacyInstance instance Eq (T a) where (==) = error "ResidueClass.Func: (==) not implemented" instance Show (T a) where show = error "ResidueClass.Func: 'show' not implemented"