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/* sys/hypot.c
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*
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* Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 Gerard Jungman, Brian Gough, Patrick Alken
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or (at
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* your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#include <config.h>
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#include <math.h>
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#include <gsl/gsl_math.h>
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double gsl_hypot (const double x, const double y)
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{
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double xabs = fabs(x) ;
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double yabs = fabs(y) ;
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double min, max;
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/* Follow the optional behavior of the ISO C standard and return
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+Inf when any of the argument is +-Inf, even if the other is NaN.
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http://pubs.opengroup.org/onlinepubs/009695399/functions/hypot.html */
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if (gsl_isinf(x) || gsl_isinf(y))
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{
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return GSL_POSINF;
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}
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if (xabs < yabs) {
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min = xabs ;
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max = yabs ;
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} else {
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min = yabs ;
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max = xabs ;
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}
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if (min == 0)
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{
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return max ;
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}
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{
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double u = min / max ;
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return max * sqrt (1 + u * u) ;
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}
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}
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double
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gsl_hypot3(const double x, const double y, const double z)
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{
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double xabs = fabs(x);
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double yabs = fabs(y);
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double zabs = fabs(z);
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double w = GSL_MAX(xabs, GSL_MAX(yabs, zabs));
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if (w == 0.0)
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{
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return (0.0);
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}
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else
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{
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double r = w * sqrt((xabs / w) * (xabs / w) +
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(yabs / w) * (yabs / w) +
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(zabs / w) * (zabs / w));
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return r;
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}
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}
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