math: Fix off-by-one error in Ilogb and Logb.
Fixes #1141.
R=rsc
CC=adg, golang-dev
https://golang.org/cl/2194047
diff --git a/src/pkg/math/all_test.go b/src/pkg/math/all_test.go
index 485f6e5..8a60bca 100644
--- a/src/pkg/math/all_test.go
+++ b/src/pkg/math/all_test.go
@@ -383,16 +383,16 @@
2.161703872847352815363655e+00,
}
var logb = []float64{
- 3.0000000000000000e+00,
- 3.0000000000000000e+00,
- -1.0000000000000000e+00,
- 3.0000000000000000e+00,
- 4.0000000000000000e+00,
+ 2.0000000000000000e+00,
+ 2.0000000000000000e+00,
+ -2.0000000000000000e+00,
2.0000000000000000e+00,
3.0000000000000000e+00,
+ 1.0000000000000000e+00,
2.0000000000000000e+00,
1.0000000000000000e+00,
- 4.0000000000000000e+00,
+ 0.0000000000000000e+00,
+ 3.0000000000000000e+00,
}
var log10 = []float64{
6.9714316642508290997617083e-01,
@@ -1806,8 +1806,9 @@
func TestIlogb(t *testing.T) {
for i := 0; i < len(vf); i++ {
- if e := Ilogb(vf[i]); frexp[i].i != e {
- t.Errorf("Ilogb(%g) = %d, want %d", vf[i], e, frexp[i].i)
+ a := frexp[i].i - 1 // adjust because fr in the interval [½, 1)
+ if e := Ilogb(vf[i]); a != e {
+ t.Errorf("Ilogb(%g) = %d, want %d", vf[i], e, a)
}
}
for i := 0; i < len(vflogbSC); i++ {
