mirror of
https://github.com/golang/go
synced 2024-10-05 20:31:20 -06:00
dfc3910afa
R=r DELTA=173 (74 added, 14 deleted, 85 changed) OCL=25753 CL=25767
50 lines
848 B
Go
50 lines
848 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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* hypot -- sqrt(p*p + q*q), but overflows only if the result does.
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* See Cleve Moler and Donald Morrison,
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* Replacing Square Roots by Pythagorean Sums
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* IBM Journal of Research and Development,
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* Vol. 27, Number 6, pp. 577-581, Nov. 1983
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*/
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// Hypot computes Sqrt(p*p + q*q), taking care to avoid
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// unnecessary overflow and underflow.
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func Hypot(p, q float64) float64 {
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if p < 0 {
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p = -p;
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}
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if q < 0 {
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q = -q;
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}
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if p < q {
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p, q = q, p;
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}
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if p == 0 {
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return 0;
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}
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pfac := p;
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q = q/p;
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r := q;
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p = 1;
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for {
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r = r*r;
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s := r+4;
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if s == 4 {
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return p*pfac;
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}
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r = r/s;
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p = p + 2*r*p;
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q = q*r;
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r = q/p;
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}
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panic("unreachable")
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}
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