| /* 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; |
| } |
| |