5db3aa6 · typeable/aeson

git.iko.soy/typeable/aeson

Encode RealFloat numbers using Scientific.fromFloatDigits

The previous code used realToFrac (fromRation . toRational) which approximates a floating point value. For example: > toRational (1.2::Double) 5404319552844595 % 4503599627370496 If you encode this Rational number to a Scientific number and render it you get: > encode (1.2::Double) "1.1999999999999999555910790149937383830547332763671875" Using Scientific.fromFloatDigits you get the expected: > encode (1.2::Double) "1.2"

commit5db3aa617ef6021737e082fc7a979c7859999b16 authorBas van Dijk <v.dijk.bas@gmail.com> dateTue 5 Nov 2013, 01:42 (13 years ago) parente202fb4

1 file changed+5−4

compare with master

unifiedsplit

Data/Aeson/Types/Instances.hs+5−4

Data/Aeson/Types/Instances.hs+5−4

@@ -55,7 +55,8 @@ import Control.Applicative ((<$>), (<*>), (<|>), pure, empty)

5555import Data.Aeson.Functions

5656import Data.Aeson.Types.Class

5757import Data.Aeson.Types.Internal

58−import Data.Scientific (Scientific, coefficient, base10Exponent)

58+import Data.Scientific (Scientific)

59+import qualified Data.Scientific as Scientific (coefficient, base10Exponent, fromFloatDigits)

5960import Data.Attoparsec.Number (Number(..))

6061import Data.Fixed

6162import Data.Hashable (Hashable(..))

@@ -158,7 +159,7 @@ instance ToJSON Double where

158159realFloatToJSON :: RealFloat a => a -> Value

159160realFloatToJSON d

160161 | isNaN d || isInfinite d = Null

161− | otherwise = Number $ realToFrac d

162+ | otherwise = Number $ Scientific.fromFloatDigits d

162163{-# INLINE realFloatToJSON #-}

163164

164165instance FromJSON Double where

@@ -780,6 +781,6 @@ scientificToNumber s

780781 | e < 0 = D $ fromInteger c / 10 ^ negate e

781782 | otherwise = I $ c * 10 ^ e

782783 where

783− e = base10Exponent s

784− c = coefficient s

784+ e = Scientific.base10Exponent s

785+ c = Scientific.coefficient s

785786{-# INLINE scientificToNumber #-}