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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
/*
* hypot -- sqrt(p*p + q*q), but overflows only if the result does.
* See Cleve Moler and Donald Morrison,
* Replacing Square Roots by Pythagorean Sums
* IBM Journal of Research and Development,
* Vol. 27, Number 6, pp. 577-581, Nov. 1983
*/
// Hypot computes Sqrt(p*p + q*q), taking care to avoid
// unnecessary overflow and underflow.
func Hypot(p, q float64) float64 {
if p < 0 {
p = -p;
}
if q < 0 {
q = -q;
}
if p < q {
p, q = q, p;
}
if p == 0 {
return 0;
}
pfac := p;
q = q/p;
r := q;
p = 1;
for {
r = r*r;
s := r+4;
if s == 4 {
return p*pfac;
}
r = r/s;
p = p + 2*r*p;
q = q*r;
r = q/p;
}
panic("unreachable")
}
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