1 /* sys/pow_int.c
2 *
3 * Copyright (C) 1996, 1997, 1998, 1999, 2000 Gerard Jungman
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 3 of the License, or (at
8 * your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
18 */
19 #include "gsl__config.h"
20 #include <math.h>
21 #include "gsl_pow_int.h"
22
23 #ifndef HIDE_INLINE_STATIC
gsl_pow_2(const double x)24 double gsl_pow_2(const double x) { return x*x; }
gsl_pow_3(const double x)25 double gsl_pow_3(const double x) { return x*x*x; }
gsl_pow_4(const double x)26 double gsl_pow_4(const double x) { double x2 = x*x; return x2*x2; }
gsl_pow_5(const double x)27 double gsl_pow_5(const double x) { double x2 = x*x; return x2*x2*x; }
gsl_pow_6(const double x)28 double gsl_pow_6(const double x) { double x2 = x*x; return x2*x2*x2; }
gsl_pow_7(const double x)29 double gsl_pow_7(const double x) { double x3 = x*x*x; return x3*x3*x; }
gsl_pow_8(const double x)30 double gsl_pow_8(const double x) { double x2 = x*x; double x4 = x2*x2; return x4*x4; }
gsl_pow_9(const double x)31 double gsl_pow_9(const double x) { double x3 = x*x*x; return x3*x3*x3; }
32 #endif
33
gsl_pow_int(double x,int n)34 double gsl_pow_int(double x, int n)
35 {
36 double value = 1.0;
37
38 if(n < 0) {
39 x = 1.0/x;
40 n = -n;
41 }
42
43 /* repeated squaring method
44 * returns 0.0^0 = 1.0, so continuous in x
45 */
46 do {
47 if(n & 1) value *= x; /* for n odd */
48 n >>= 1;
49 x *= x;
50 } while (n);
51
52 return value;
53 }
54
55