12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455 |
- /* 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 "gsl__config.h"
- #include <math.h>
- #include "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;
- }
|