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https://github.com/golang/go
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61 lines
1.4 KiB
Go
61 lines
1.4 KiB
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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export pow10
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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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const tabsize = 70;
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var initdone bool;
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var tab[tabsize] float64;
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//{
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// 1.0e0, 1.0e1, 1.0e2, 1.0e3, 1.0e4, 1.0e5, 1.0e6, 1.0e7, 1.0e8, 1.0e9,
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// 1.0e10,1.0e11,1.0e12,1.0e13,1.0e14,1.0e15,1.0e16,1.0e17,1.0e18,1.0e19,
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// 1.0e20,1.0e21,1.0e22,1.0e23,1.0e24,1.0e25,1.0e26,1.0e27,1.0e28,1.0e29,
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// 1.0e30,1.0e31,1.0e32,1.0e33,1.0e34,1.0e35,1.0e36,1.0e37,1.0e38,1.0e39,
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// 1.0e40,1.0e41,1.0e42,1.0e43,1.0e44,1.0e45,1.0e46,1.0e47,1.0e48,1.0e49,
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// 1.0e50,1.0e51,1.0e52,1.0e53,1.0e54,1.0e55,1.0e56,1.0e57,1.0e58,1.0e59,
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// 1.0e60,1.0e61,1.0e62,1.0e63,1.0e64,1.0e65,1.0e66,1.0e67,1.0e68,1.0e69,
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//};
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func init();
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func
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pow10(e int) float64
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{
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if !initdone {
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init();
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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 < tabsize {
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return tab[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
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init()
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{
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initdone = true;
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tab[0] = 1.0e0;
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tab[1] = 1.0e1;
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for i:=2; i<tabsize; i++ {
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m := i/2;
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tab[i] = tab[m] * tab[i-m];
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}
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}
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