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Source file 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
  
  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
  
  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)
  }
  

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