mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-30 08:40:07 +00:00
65 lines
2.2 KiB
C
65 lines
2.2 KiB
C
/* Implementation of gamma function according to ISO C.
|
|
Copyright (C) 1997,1999,2001,2003,2004,2011 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, see
|
|
<http://www.gnu.org/licenses/>. */
|
|
|
|
#include <math.h>
|
|
#include <math_private.h>
|
|
|
|
|
|
long double
|
|
__ieee754_gammal_r (long 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. */
|
|
u_int32_t es, hx, lx;
|
|
|
|
GET_LDOUBLE_WORDS (es, hx, lx, x);
|
|
|
|
if (__builtin_expect (((es & 0x7fff) | hx | lx) == 0, 0))
|
|
{
|
|
/* Return value for x == 0 is Inf with divide by zero exception. */
|
|
*signgamp = 0;
|
|
return 1.0 / x;
|
|
}
|
|
if (__builtin_expect (es == 0xffffffff && ((hx & 0x7fffffff) | lx) == 0, 0))
|
|
{
|
|
/* x == -Inf. According to ISO this is NaN. */
|
|
*signgamp = 0;
|
|
return x - x;
|
|
}
|
|
if (__builtin_expect ((es & 0x7fff) == 0x7fff, 0)
|
|
&& ((hx & 0x7fffffff) | lx) != 0)
|
|
{
|
|
/* NaN, return it. */
|
|
*signgamp = 0;
|
|
return x;
|
|
}
|
|
if (__builtin_expect ((es & 0x8000) != 0, 0)
|
|
&& x < 0xffffffff && __rintl (x) == x)
|
|
{
|
|
/* Return value for integer x < 0 is NaN with invalid exception. */
|
|
*signgamp = 0;
|
|
return (x - x) / (x - x);
|
|
}
|
|
|
|
/* XXX FIXME. */
|
|
return __ieee754_expl (__ieee754_lgammal_r (x, signgamp));
|
|
}
|
|
strong_alias (__ieee754_gammal_r, __gammal_r_finite)
|