| /* Implementation of gamma function according to ISO C. |
| Copyright (C) 1997, 1999, 2001, 2004 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997. |
| |
| 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, write to the Free |
| Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |
| 02111-1307 USA. */ |
| |
| #include <math.h> |
| #include <math_private.h> |
| |
| |
| double |
| __ieee754_gamma_r (double x, int *signgamp) |
| { |
| /* We don't have a real gamma implementation now. We'll use lgamma |
| and the exp function. But due to the required boundary |
| conditions we must check some values separately. */ |
| int32_t hx; |
| u_int32_t lx; |
| |
| EXTRACT_WORDS (hx, lx, x); |
| |
| if (((hx & 0x7fffffff) | lx) == 0) |
| { |
| /* Return value for x == 0 is Inf with divide by zero exception. */ |
| *signgamp = 0; |
| return 1.0 / x; |
| } |
| if (hx < 0 && (u_int32_t) hx < 0xfff00000 && __rint (x) == x) |
| { |
| /* Return value for integer x < 0 is NaN with invalid exception. */ |
| *signgamp = 0; |
| return (x - x) / (x - x); |
| } |
| if ((unsigned int) hx == 0xfff00000 && lx==0) |
| { |
| /* x == -Inf. According to ISO this is NaN. */ |
| *signgamp = 0; |
| return x - x; |
| } |
| |
| /* XXX FIXME. */ |
| return __ieee754_exp (__ieee754_lgamma_r (x, signgamp)); |
| } |