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87969c8c | 1 | /* Implementation of gamma function according to ISO C. |
92920cc6 | 2 | Copyright (C) 1997, 1999, 2002, 2004 Free Software Foundation, Inc. |
87969c8c | 3 | This file is part of the GNU C Library. |
4 | Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997 and | |
5 | Jakub Jelinek <jj@ultra.linux.cz, 1999. | |
6 | ||
7 | The GNU C Library is free software; you can redistribute it and/or | |
8 | modify it under the terms of the GNU Lesser General Public | |
9 | License as published by the Free Software Foundation; either | |
10 | version 2.1 of the License, or (at your option) any later version. | |
11 | ||
12 | The GNU C Library is distributed in the hope that it will be useful, | |
13 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
15 | Lesser General Public License for more details. | |
16 | ||
17 | You should have received a copy of the GNU Lesser General Public | |
18 | License along with the GNU C Library; if not, write to the Free | |
19 | Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA | |
20 | 02111-1307 USA. */ | |
21 | ||
22 | #include "quadmath-imp.h" | |
23 | ||
24 | ||
25 | __float128 | |
26 | tgammaq (__float128 x) | |
27 | { | |
28 | /* We don't have a real gamma implementation now. We'll use lgamma | |
29 | and the exp function. But due to the required boundary | |
30 | conditions we must check some values separately. */ | |
31 | int64_t hx; | |
32 | uint64_t lx; | |
4a2f7ea2 | 33 | __float128 res; |
34 | int sign; | |
87969c8c | 35 | |
36 | GET_FLT128_WORDS64 (hx, lx, x); | |
37 | ||
38 | if (((hx & 0x7fffffffffffffffLL) | lx) == 0) | |
39 | /* Return value for x == 0 is Inf with divide by zero exception. */ | |
40 | return 1.0 / x; | |
41 | ||
42 | if (hx < 0 && (uint64_t) hx < 0xffff000000000000ULL && rintq (x) == x) | |
43 | /* Return value for integer x < 0 is NaN with invalid exception. */ | |
44 | return (x - x) / (x - x); | |
45 | ||
46 | if (hx == 0xffff000000000000ULL && lx == 0) | |
47 | /* x == -Inf. According to ISO this is NaN. */ | |
48 | return x - x; | |
49 | ||
50 | /* XXX FIXME. */ | |
4a2f7ea2 | 51 | res = expq (lgammaq (x)); |
52 | return signbitq (x) ? -res : res; | |
87969c8c | 53 | } |