| /* Compute a product of X, X+1, ..., with an error estimate. |
| Copyright (C) 2013-2014 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| |
| The GNU C Library is free software; you can redistribute it and/or |
| modify it under the terms of the GNU Lesser General Public |
| License as published by the Free Software Foundation; either |
| version 2.1 of the License, or (at your option) any later version. |
| |
| The GNU C Library 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 |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public |
| License along with the GNU C Library; if not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include <math.h> |
| #include <math_private.h> |
| |
| /* Compute the product of X + X_EPS, X + X_EPS + 1, ..., X + X_EPS + N |
| - 1, in the form R * (1 + *EPS) where the return value R is an |
| approximation to the product and *EPS is set to indicate the |
| approximate error in the return value. X is such that all the |
| values X + 1, ..., X + N - 1 are exactly representable, and X_EPS / |
| X is small enough that factors quadratic in it can be |
| neglected. */ |
| |
| long double |
| __gamma_productl (long double x, long double x_eps, int n, long double *eps) |
| { |
| long double ret = x; |
| *eps = x_eps / x; |
| for (int i = 1; i < n; i++) |
| { |
| *eps += x_eps / (x + i); |
| ret *= x + i; |
| /* FIXME: no error estimates for the multiplication. */ |
| } |
| return ret; |
| } |
