diff options
Diffstat (limited to 'libgo/go/math/logb.go')
| -rw-r--r-- | libgo/go/math/logb.go | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/libgo/go/math/logb.go b/libgo/go/math/logb.go index 22ec06325d5..072281ddf9f 100644 --- a/libgo/go/math/logb.go +++ b/libgo/go/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 + 1)) + 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 + 1) + 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 } |