Make the `Float` and `Double` implementations of `abs` handle -0.0 correctly per IEEE-754. --- libraries/base/GHC/Float.lhs | 12 ++++++++---- libraries/base/changelog.md | 2 ++ 2 files changed, 10 insertions(+), 4 deletions(-) diff --git a/libraries/base/GHC/Float.lhs b/libraries/base/GHC/Float.lhs index e0c4f4a..442e13c 100644 --- a/libraries/base/GHC/Float.lhs +++ b/libraries/base/GHC/Float.lhs @@ -205,8 +205,10 @@ instance Num Float where (-) x y = minusFloat x y negate x = negateFloat x (*) x y = timesFloat x y - abs x | x >= 0.0 = x - | otherwise = negateFloat x + abs x + | isNegativeZero x = 0 + | x >= 0.0 = x + | otherwise = negateFloat x signum x | x == 0.0 = 0 | x > 0.0 = 1 | otherwise = negate 1 @@ -370,8 +372,10 @@ instance Num Double where (-) x y = minusDouble x y negate x = negateDouble x (*) x y = timesDouble x y - abs x | x >= 0.0 = x - | otherwise = negateDouble x + abs x + | isNegativeZero x = 0 + | x >= 0.0 = x + | otherwise = negateDouble x signum x | x == 0.0 = 0 | x > 0.0 = 1 | otherwise = negate 1 diff --git a/libraries/base/changelog.md b/libraries/base/changelog.md index a72e4e6..9eb279e 100644 --- a/libraries/base/changelog.md +++ b/libraries/base/changelog.md @@ -10,6 +10,8 @@ * Weaken RealFloat constraints on some `Data.Complex` functions + * Make `abs` handle -0.0 correctly for `Float` and `Double`. + ## 4.7.0.0 *Apr 2014* * Bundled with GHC 7.8.1 -- 1.8.3.2