// 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 ( float64) float64 {
	if haveArchLog10 {
		return archLog10()
	}
	return log10()
}

func log10( float64) float64 {
	return Log() * (1 / Ln10)
}

// Log2 returns the binary logarithm of x.
// The special cases are the same as for [Log].
func ( float64) float64 {
	if haveArchLog2 {
		return archLog2()
	}
	return log2()
}

func log2( float64) float64 {
	,  := Frexp()
	// 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  == 0.5 {
		return float64( - 1)
	}
	return Log()*(1/Ln2) + float64()
}