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| author | Bodigrim <andrew.lelechenko@gmail.com> | 2023-05-09 21:09:10 +0100 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2023-05-11 04:13:24 -0400 |
| commit | 630b1fea1e41a1e00860a30742b6ab8ade8a0de0 (patch) | |
| tree | 9694f4f4460253327c7ed7a1f75fe092a8f6e432 /libraries | |
| parent | bd0b056ea56643bcca1a23b78f72576f9459ce1b (diff) | |
| download | haskell-630b1fea1e41a1e00860a30742b6ab8ade8a0de0.tar.gz | |
Document unlawfulness of instance Num Fixed
Fixes #22712
Diffstat (limited to 'libraries')
| -rw-r--r-- | libraries/base/Data/Fixed.hs | 7 | ||||
| -rw-r--r-- | libraries/base/GHC/Float.hs | 4 |
2 files changed, 9 insertions, 2 deletions
diff --git a/libraries/base/Data/Fixed.hs b/libraries/base/Data/Fixed.hs index bb45d20a38..a34f73ecd2 100644 --- a/libraries/base/Data/Fixed.hs +++ b/libraries/base/Data/Fixed.hs @@ -163,6 +163,13 @@ instance Enum (Fixed a) where enumFromThenTo (MkFixed a) (MkFixed b) (MkFixed c) = fmap MkFixed (enumFromThenTo a b c) -- | @since 2.01 +-- +-- Multiplication is not associative or distributive: +-- +-- >>> (0.2 * 0.6 :: Deci) * 0.9 == 0.2 * (0.6 * 0.9) +-- False +-- >>> (0.1 + 0.1 :: Deci) * 0.5 == 0.1 * 0.5 + 0.1 * 0.5 +-- False instance (HasResolution a) => Num (Fixed a) where (MkFixed a) + (MkFixed b) = MkFixed (a + b) (MkFixed a) - (MkFixed b) = MkFixed (a - b) diff --git a/libraries/base/GHC/Float.hs b/libraries/base/GHC/Float.hs index 195c23b1f4..8045216b25 100644 --- a/libraries/base/GHC/Float.hs +++ b/libraries/base/GHC/Float.hs @@ -279,7 +279,7 @@ class (RealFrac a, Floating a) => RealFloat a where -- -- This instance implements IEEE 754 standard with all its usual pitfalls -- about NaN, infinities and negative zero. --- Neither addition not multiplication are associative or distributive: +-- Neither addition nor multiplication are associative or distributive: -- -- >>> (0.1 + 0.1 :: Float) + 0.5 == 0.1 + (0.1 + 0.5) -- False @@ -533,7 +533,7 @@ instance Show Float where -- -- This instance implements IEEE 754 standard with all its usual pitfalls -- about NaN, infinities and negative zero. --- Neither addition not multiplication are associative or distributive: +-- Neither addition nor multiplication are associative or distributive: -- -- >>> (0.1 + 0.1) + 0.4 == 0.1 + (0.1 + 0.4) -- False |