/* 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 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>
/* Compile all the inline functions */
#define COMPILE_INLINE_STATIC
#include "build.h"
#include <gsl/gsl_pow_int.h>
double gsl_pow_int(double x, int n)
{
unsigned int un;
if(n < 0) {
x = 1.0/x;
un = -n;
} else {
un = n;
}
return gsl_pow_uint(x, un);
}
double gsl_pow_uint(double x, unsigned int n)
{
double value = 1.0;
/* 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;
}