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d705269e | 1 | /* Implementation of gamma function according to ISO C. |
52e1b618 | 2 | Copyright (C) 1997, 1999, 2002 Free Software Foundation, Inc. |
c131718c | 3 | This file is part of the GNU C Library. |
abfbdde1 UD |
4 | Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997 and |
5 | Jakub Jelinek <jj@ultra.linux.cz, 1999. | |
c131718c UD |
6 | |
7 | The GNU C Library is free software; you can redistribute it and/or | |
41bdb6e2 AJ |
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. | |
c131718c UD |
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 | |
41bdb6e2 | 15 | Lesser General Public License for more details. |
c131718c | 16 | |
41bdb6e2 AJ |
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. */ | |
c131718c | 21 | |
d705269e UD |
22 | #include <math.h> |
23 | #include <math_private.h> | |
24 | ||
25 | ||
26 | long double | |
27 | __ieee754_gammal_r (long double x, int *signgamp) | |
28 | { | |
29 | /* We don't have a real gamma implementation now. We'll use lgamma | |
30 | and the exp function. But due to the required boundary | |
31 | conditions we must check some values separately. */ | |
abfbdde1 UD |
32 | int64_t hx; |
33 | u_int64_t lx; | |
d705269e | 34 | |
abfbdde1 | 35 | GET_LDOUBLE_WORDS64 (hx, lx, x); |
d705269e | 36 | |
abfbdde1 | 37 | if (((hx & 0x7fffffffffffffffLL) | lx) == 0) |
b3fc5f84 UD |
38 | { |
39 | /* Return value for x == 0 is NaN with invalid exception. */ | |
40 | *signgamp = 0; | |
41 | return x / x; | |
42 | } | |
abfbdde1 | 43 | if (hx < 0 && (u_int64_t) hx < 0xffff000000000000ULL && __rintl (x) == x) |
d705269e UD |
44 | { |
45 | /* Return value for integer x < 0 is NaN with invalid exception. */ | |
b3fc5f84 | 46 | *signgamp = 0; |
d705269e UD |
47 | return (x - x) / (x - x); |
48 | } | |
52e1b618 UD |
49 | if (hx == 0xffff000000000000ULL && lx == 0) |
50 | { | |
51 | /* x == -Inf. According to ISO this is NaN. */ | |
52 | *signgamp = 0; | |
53 | return x - x; | |
54 | } | |
d705269e UD |
55 | |
56 | /* XXX FIXME. */ | |
57 | return __ieee754_expl (__ieee754_lgammal_r (x, signgamp)); | |
58 | } |