ref: 51f905138babfc67f3291a40c8b5ddd7ec85b73d
dir: /lib/Numeric/Natural.hs/
module Numeric.Natural
( Natural
, minusNaturalMaybe
) where
import Prelude(); import MiniPrelude
import Data.Integer
import Data.Real
import Control.Exception
newtype Natural = N Integer
deriving (Eq, Ord)
instance Show Natural where
showsPrec p (N i) = showsPrec p i
instance Num Natural where
N x + N y = N (x + y)
N x - N y | y > x = throw Underflow
N x * N y = N (x * y)
abs x = x
signum x = if x > 0 then 1 else 0
fromInteger x | x < 0 = throw Underflow
| otherwise = N x
instance Enum Natural where
toEnum = fromInteger . toInteger
fromEnum = fromInteger . toInteger
instance Integral Natural where
toInteger (N i) = i
quotRem (N x) (N y) = (N q, N r) where (q, r) = quotRem x y
instance Real Natural where
toRational (N i) = toRational i
minusNaturalMaybe :: Natural -> Natural -> Maybe Natural
minusNaturalMaybe x y | x < y = Nothing
| otherwise = Just (x - y)