| /* Compute a product of X, X+1, ..., with an error estimate. |

| Copyright (C) 2013-2018 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 "quadmath-imp.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. */ |

| |

| __float128 |

| __quadmath_gamma_productq (__float128 x, __float128 x_eps, int n, __float128 *eps) |

| { |

| SET_RESTORE_ROUNDF128 (FE_TONEAREST); |

| __float128 ret = x; |

| *eps = x_eps / x; |

| for (int i = 1; i < n; i++) |

| { |

| *eps += x_eps / (x + i); |

| __float128 lo; |

| mul_splitq (&ret, &lo, ret, x + i); |

| *eps += lo / ret; |

| } |

| return ret; |

| } |