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- /* 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 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.
- */
- /* Author: G. Jungman */
- #include "gsl__config.h"
- #include "gsl_math.h"
- #include "gsl_errno.h"
- #include "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 "gsl_specfunc__eval.h"
- double gsl_sf_pow_int(const double x, const int n)
- {
- EVAL_RESULT(gsl_sf_pow_int_e(x, n, &result));
- }
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