| /* specfunc/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. |
| */ |
| |
| /* Author: G. Jungman */ |
| |
| #include <config.h> |
| #include <gsl/gsl_math.h> |
| #include <gsl/gsl_errno.h> |
| #include <gsl/gsl_sf_pow_int.h> |
| |
| |
| /*-*-*-*-*-*-*-*-*-*-*-* Functions w/ Error handling *-*-*-*-*-*-*-*-*-*-*-*/ |
| |
| int gsl_sf_pow_int_e(double x, int n, gsl_sf_result * result) |
| { |
| double value = 1.0; |
| int count = 0; |
| |
| /* CHECK_POINTER(result) */ |
| |
| |
| if(n < 0) { |
| n = -n; |
| |
| if(x == 0.0) { |
| double u = 1.0 / x; |
| result->val = (n % 2) ? u : (u * u) ; /* correct sign of infinity */ |
| result->err = GSL_POSINF; |
| GSL_ERROR ("overflow", GSL_EOVRFLW); |
| } |
| |
| x = 1.0/x; |
| } |
| |
| /* repeated squaring method |
| * returns 0.0^0 = 1.0, so continuous in x |
| */ |
| do { |
| if(GSL_IS_ODD(n)) value *= x; |
| n >>= 1; |
| x *= x; |
| ++count; |
| } while (n); |
| |
| result->val = value; |
| result->err = 2.0 * GSL_DBL_EPSILON * (count + 1.0) * fabs(value); |
| |
| return GSL_SUCCESS; |
| } |
| |
| /*-*-*-*-*-*-*-*-*-* Functions w/ Natural Prototypes *-*-*-*-*-*-*-*-*-*-*/ |
| |
| #include "eval.h" |
| |
| double gsl_sf_pow_int(const double x, const int n) |
| { |
| EVAL_RESULT(gsl_sf_pow_int_e(x, n, &result)); |
| } |