golang log10 代码
文件路径：/src/math/log10.go
/ Copyright 2009 The Go Authors. All rights reserved.
/ Use of this source code is governed by a BSD-style
/ license that can be found in the LICENSE file.
package math
/ Log10 returns the decimal logarithm of x.
/ The special cases are the same as for Log.
func Log10(x float64) float64 {
if haveArchLog10 {
return archLog10(x)
}
return log10(x)
}
func log10(x float64) float64 {
return Log(x) * (1 / Ln10)
}
/ Log2 returns the binary logarithm of x.
/ The special cases are the same as for Log.
func Log2(x float64) float64 {
if haveArchLog2 {
return archLog2(x)
}
return log2(x)
}
func log2(x float64) float64 {
frac, exp := Frexp(x)
/ Make sure exact powers of two give an exact answer.
/ Don't depend on Log(0.5)*(1/Ln2)+exp being exactly exp-1.
if frac == 0.5 {
return float64(exp - 1)
}
return Log(frac)*(1/Ln2) + float64(exp)
}