41 lines
828 B
Go
41 lines
828 B
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package math
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// This table might overflow 127-bit exponent representations.
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// In that case, truncate it after 1.0e38.
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var pow10tab [70]float64
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// Pow10 returns 10**e, the base-10 exponential of e.
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//
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// Special cases are:
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// Pow10(e) = +Inf for e > 309
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// Pow10(e) = 0 for e < -324
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func Pow10(e int) float64 {
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if e <= -325 {
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return 0
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} else if e > 309 {
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return Inf(1)
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}
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if e < 0 {
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return 1 / Pow10(-e)
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}
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if e < len(pow10tab) {
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return pow10tab[e]
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}
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m := e / 2
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return Pow10(m) * Pow10(e-m)
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}
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func init() {
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pow10tab[0] = 1.0e0
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pow10tab[1] = 1.0e1
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for i := 2; i < len(pow10tab); i++ {
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m := i / 2
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pow10tab[i] = pow10tab[m] * pow10tab[i-m]
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}
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}
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