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38 lines
886 B
Go
38 lines
886 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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/*
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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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* it is important to get all one can from this
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* routine since it is used in atof to scale numbers.
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* the presumption is that GO converts fp numbers better
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* than multipication of lower powers of 10.
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*/
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var pow10tab [70]float64;
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// Pow10 returns 10**x, the base-10 exponential of x.
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func Pow10(e int) float64 {
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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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