Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Fix the total order comparison for arbitrary floating point #703

Merged
merged 1 commit into from
Jun 7, 2024
Merged

Fix the total order comparison for arbitrary floating point #703

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
25 changes: 8 additions & 17 deletions Data/SBV/Core/SizedFloats.hs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -229,27 +229,18 @@ arbFPIsEqualObjectH (FP eb sb a) (FP eb' sb' b) = case (eb, sb) `compare` (eb',
EQ | BF.bfIsNaN a -> BF.bfIsNaN b
| BF.bfIsZero a && BF.bfIsNeg a -> BF.bfIsZero b && BF.bfIsNeg b
| BF.bfIsZero a && BF.bfIsPos a -> BF.bfIsZero b && BF.bfIsPos b
| BF.bfIsInf a -> BF.bfIsInf b
| True -> a == b

-- | Ordering for arbitrary floats, avoiding the +0/-0/NaN issues. Note that this is
-- essentially used for indexing into a map, so we need to be total. Thus,
-- the order we pick is:
-- NaN -oo -0 +0 +oo
-- The placement of NaN here is questionable, but immaterial.
-- essentially used for indexing into a map, so we need to be total.
--
-- This function uses the bfCompare function provided by the libBF. As per the libBF's documentation,
-- it has the semantics: -0 < 0, NaN == NaN, and NaN is larger than all other numbers.
arbFPCompareObjectH :: FP -> FP -> Ordering
arbFPCompareObjectH fa@(FP eb sb a) fb@(FP eb' sb' b) = case (eb, sb) `compare` (eb', sb') of
LT -> LT
GT -> GT
EQ | fa `arbFPIsEqualObjectH` fb -> EQ
| BF.bfIsNaN a -> LT
| BF.bfIsNaN b -> GT
| BF.bfIsZero a && BF.bfIsNeg a && BF.bfIsZero b -> LT
| BF.bfIsZero b && BF.bfIsNeg b && BF.bfIsZero a -> GT
| BF.bfIsInf a -> GT
| BF.bfIsInf b -> LT
| True -> a `compare` b

arbFPCompareObjectH (FP eb sb a) (FP eb' sb' b) = case (eb, sb) `compare` (eb', sb') of
LT -> LT
GT -> GT
EQ -> BF.bfCompare a b
-- | Compute the signum of a big float
bfSignum :: BigFloat -> BigFloat
bfSignum r | BF.bfIsNaN r = r
Expand Down
Loading