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/* sys/pow_int.c
*
* Copyright (C) 1996, 1997, 1998, 1999, 2000 Gerard Jungman
*
* 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 2 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_pow_int.h>
#ifndef HIDE_INLINE_STATIC
double gsl_pow_2(const double x) { return x*x; }
double gsl_pow_3(const double x) { return x*x*x; }
double gsl_pow_4(const double x) { double x2 = x*x; return x2*x2; }
double gsl_pow_5(const double x) { double x2 = x*x; return x2*x2*x; }
double gsl_pow_6(const double x) { double x2 = x*x; return x2*x2*x2; }
double gsl_pow_7(const double x) { double x3 = x*x*x; return x3*x3*x; }
double gsl_pow_8(const double x) { double x2 = x*x; double x4 = x2*x2; return x4*x4; }
double gsl_pow_9(const double x) { double x3 = x*x*x; return x3*x3*x3; }
#endif
double gsl_pow_int(double x, int n)
{
double value = 1.0;
if(n < 0) {
x = 1.0/x;
n = -n;
}
/* repeated squaring method
* returns 0.0^0 = 1.0, so continuous in x
*/
do {
if(n & 1) value *= x; /* for n odd */
n >>= 1;
x *= x;
} while (n);
return value;
}
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