File: log10.go

package info (click to toggle)
gcc-arm-none-eabi 15%3A14.2.rel1-1
  • links: PTS, VCS
  • area: main
  • in suites: sid, trixie
  • size: 1,099,328 kB
  • sloc: cpp: 3,627,108; ansic: 2,571,498; ada: 834,230; f90: 235,082; makefile: 79,231; asm: 74,984; xml: 51,692; exp: 39,736; sh: 33,298; objc: 15,629; python: 15,069; fortran: 14,429; pascal: 7,003; awk: 5,070; perl: 3,106; ml: 285; lisp: 253; lex: 204; haskell: 135
file content (36 lines) | stat: -rw-r--r-- 837 bytes parent folder | download | duplicates (5) 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
 
// 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.

//extern log10
func libc_log10(float64) float64

func Log10(x float64) float64 {
	return libc_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 {
	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)
}