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Diffstat (limited to 'gsl-1.9/specfunc/pow_int.c')
-rw-r--r-- | gsl-1.9/specfunc/pow_int.c | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/gsl-1.9/specfunc/pow_int.c b/gsl-1.9/specfunc/pow_int.c new file mode 100644 index 0000000..720b2e3 --- /dev/null +++ b/gsl-1.9/specfunc/pow_int.c @@ -0,0 +1,74 @@ +/* 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)); +} |