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// 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]
        }
}