rounded-hw-0.4.0.3: src/Numeric/Rounded/Hardware/Internal/FloatUtil.hs

{-# LANGUAGE CPP #-}
{-# LANGUAGE NumericUnderscores #-}
module Numeric.Rounded.Hardware.Internal.FloatUtil
  ( nextUp
  , nextDown
  , nextTowardZero
  , distanceUlp
  , fusedMultiplyAdd
  ) where
import           Data.Ratio
import           Numeric.Floating.IEEE

distanceUlp :: RealFloat a => a -> a -> Maybe Integer
distanceUlp x y
  | isInfinite x || isInfinite y || isNaN x || isNaN y = Nothing
  | otherwise = let m = min (abs x) (abs y)
                    ulp | m == 0 = minPositive
                        | otherwise = encodeFloat 1 (max (fst (floatRange m)) (exponent m) - floatDigits m) `asTypeOf` m
                    v = (toRational y - toRational x) / toRational ulp
                in if denominator v == 1
                   then Just (abs (numerator v))
                   else error "distanceUlp"