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Source file src/math/pow10.go

Documentation: math

  // 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
  
  // This table might overflow 127-bit exponent representations.
  // In that case, truncate it after 1.0e38.
  var pow10tab [70]float64
  
  // Pow10 returns 10**e, the base-10 exponential of e.
  //
  // Special cases are:
  //	Pow10(e) = +Inf for e > 309
  //	Pow10(e) = 0 for e < -324
  func Pow10(e int) float64 {
  	if e <= -325 {
  		return 0
  	} else if e > 309 {
  		return Inf(1)
  	}
  
  	if e < 0 {
  		return 1 / Pow10(-e)
  	}
  	if e < len(pow10tab) {
  		return pow10tab[e]
  	}
  	m := e / 2
  	return Pow10(m) * Pow10(e-m)
  }
  
  func init() {
  	pow10tab[0] = 1.0e0
  	pow10tab[1] = 1.0e1
  	for i := 2; i < len(pow10tab); i++ {
  		m := i / 2
  		pow10tab[i] = pow10tab[m] * pow10tab[i-m]
  	}
  }
  

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