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| author | David Chase <drchase@google.com> | 2019-03-13 16:46:10 -0400 |
|---|---|---|
| committer | David Chase <drchase@google.com> | 2019-03-15 14:52:51 +0000 |
| commit | 653579138555ff2728ba16f841b640e06deab8df (patch) | |
| tree | 5f87491cc7412f08e21877a33d177f4646a1931f /src | |
| parent | 9d9d4eeb87ed5dae09e26d744ea7d6caf9b182dc (diff) | |
| download | go-653579138555ff2728ba16f841b640e06deab8df.tar.xz | |
math: fix math.Remainder(-x,x) (for Inf > x > 0)
Modify the |x| == |y| case to return -0 when x < 0.
Fixes #30814.
Change-Id: Ic4cd48001e0e894a12b5b813c6a1ddc3a055610b
Reviewed-on: https://go-review.googlesource.com/c/go/+/167479
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
Diffstat (limited to 'src')
| -rw-r--r-- | src/math/all_test.go | 14 | ||||
| -rw-r--r-- | src/math/remainder.go | 4 |
2 files changed, 18 insertions, 0 deletions
diff --git a/src/math/all_test.go b/src/math/all_test.go index ed42941780..208c8233e0 100644 --- a/src/math/all_test.go +++ b/src/math/all_test.go @@ -2795,6 +2795,20 @@ func TestRemainder(t *testing.T) { if f := Remainder(5.9790119248836734e+200, 1.1258465975523544); -0.4810497673014966 != f { t.Errorf("Remainder(5.9790119248836734e+200, 1.1258465975523544) = %g, want -0.4810497673014966", f) } + // verify that sign is correct when r == 0. + test := func(x, y float64) { + if r := Remainder(x, y); r == 0 && Signbit(r) != Signbit(x) { + t.Errorf("Remainder(x=%f, y=%f) = %f, sign of (zero) result should agree with sign of x", x, y, r) + } + } + for x := 0.0; x <= 3.0; x += 1 { + for y := 1.0; y <= 3.0; y += 1 { + test(x, y) + test(x, -y) + test(-x, y) + test(-x, -y) + } + } } func TestRound(t *testing.T) { diff --git a/src/math/remainder.go b/src/math/remainder.go index 504fdda7df..7c77d6eb3b 100644 --- a/src/math/remainder.go +++ b/src/math/remainder.go @@ -57,6 +57,10 @@ func remainder(x, y float64) float64 { y = -y } if x == y { + if sign { + zero := 0.0 + return -zero + } return 0 } if y <= HalfMax { |