math: more special cases for signed zero
R=rsc
CC=golang-dev
https://golang.org/cl/937042
diff --git a/src/pkg/math/asin.go b/src/pkg/math/asin.go
index 63cac1c..3bace8f 100644
--- a/src/pkg/math/asin.go
+++ b/src/pkg/math/asin.go
@@ -14,16 +14,20 @@
// Asin returns the arcsine of x.
//
-// Special case is:
+// Special cases are:
+// Asin(±0) = ±0
// Asin(x) = NaN if x < -1 or x > 1
func Asin(x float64) float64 {
+ if x == 0 {
+ return x // special case
+ }
sign := false
if x < 0 {
x = -x
sign = true
}
if x > 1 {
- return NaN()
+ return NaN() // special case
}
temp := Sqrt(1 - x*x)
