Imported Upstream version 2011-02-01.1upstream/2011-02-01.1

1 files changed, 11 insertions, 4 deletions

diff --git a/src/pkg/math/logb.go b/src/pkg/math/logb.go
index 9e4651517..072281ddf 100644
--- a/src/pkg/math/logb.go
+++ b/src/pkg/math/logb.go
@@ -4,7 +4,7 @@
 
 package math
 
-// Logb(x) returns the binary exponent of non-zero x.
+// Logb(x) returns the binary exponent of x.
 //
 // Special cases are:
 //	Logb(±Inf) = +Inf
@@ -22,10 +22,10 @@ func Logb(x float64) float64 {
 	case x != x: // IsNaN(x):
 		return x
 	}
-	return float64(int((Float64bits(x)>>shift)&mask) - bias)
+	return float64(ilogb(x))
 }
 
-// Ilogb(x) returns the binary exponent of non-zero x as an integer.
+// Ilogb(x) returns the binary exponent of x as an integer.
 //
 // Special cases are:
 //	Ilogb(±Inf) = MaxInt32
@@ -43,5 +43,12 @@ func Ilogb(x float64) int {
 	case x < -MaxFloat64 || x > MaxFloat64: // IsInf(x, 0):
 		return MaxInt32
 	}
-	return int((Float64bits(x)>>shift)&mask) - bias
+	return ilogb(x)
+}
+
+// logb returns the binary exponent of x. It assumes x is finite and
+// non-zero.
+func ilogb(x float64) int {
+	x, exp := normalize(x)
+	return int((Float64bits(x)>>shift)&mask) - bias + exp
 }