/* sys/hypot.c

 * 

 * Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 Gerard Jungman, Brian Gough, Patrick Alken

 * 

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation; either version 3 of the License, or (at

 * your option) any later version.

 * 

 * This program is distributed in the hope that it will be useful, but

 * WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * General Public License for more details.

 * 

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

 */

#include <config.h>

#include <math.h>

#include <gsl/gsl_math.h>

double gsl_hypot (const double x, const double y)

{

  double xabs = fabs(x) ;

  double yabs = fabs(y) ;

  double min, max;

  /* Follow the optional behavior of the ISO C standard and return

     +Inf when any of the argument is +-Inf, even if the other is NaN.

     http://pubs.opengroup.org/onlinepubs/009695399/functions/hypot.html */

  if (gsl_isinf(x) || gsl_isinf(y)) 

    {

      return GSL_POSINF;

    }

  if (xabs < yabs) {

    min = xabs ;

    max = yabs ;

  } else {

    min = yabs ;

    max = xabs ;

  }

  if (min == 0) 

    {

      return max ;

    }

  {

    double u = min / max ;

    return max * sqrt (1 + u * u) ;

  }

}

double

gsl_hypot3(const double x, const double y, const double z)

{

  double xabs = fabs(x);

  double yabs = fabs(y);

  double zabs = fabs(z);

  double w = GSL_MAX(xabs, GSL_MAX(yabs, zabs));

  if (w == 0.0)

    {

      return (0.0);

    }

  else

    {

      double r = w * sqrt((xabs / w) * (xabs / w) +

                          (yabs / w) * (yabs / w) +

                          (zabs / w) * (zabs / w));

      return r;

    }

}