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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]

        }

}