1/* Implementation of gamma function according to ISO C.
2   Copyright (C) 1997, 1999, 2001, 2004 Free Software Foundation, Inc.
3   This file is part of the GNU C Library.
4   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
5
6   The GNU C Library is free software; you can redistribute it and/or
7   modify it under the terms of the GNU Lesser General Public
8   License as published by the Free Software Foundation; either
9   version 2.1 of the License, or (at your option) any later version.
10
11   The GNU C Library is distributed in the hope that it will be useful,
12   but WITHOUT ANY WARRANTY; without even the implied warranty of
13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14   Lesser General Public License for more details.
15
16   You should have received a copy of the GNU Lesser General Public
17   License along with the GNU C Library; if not, write to the Free
18   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
19   02111-1307 USA.  */
20
21#include <math.h>
22#include <math_private.h>
23
24
25float
26__ieee754_gammaf_r (float x, int *signgamp)
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  int32_t hx;
32
33  GET_FLOAT_WORD (hx, x);
34
35  if ((hx & 0x7fffffff) == 0)
36    {
37      /* Return value for x == 0 is Inf with divide by zero exception.  */
38      *signgamp = 0;
39      return 1.0 / x;
40    }
41  if (hx < 0 && (u_int32_t) hx < 0xff800000 && __rintf (x) == x)
42    {
43      /* Return value for integer x < 0 is NaN with invalid exception.  */
44      *signgamp = 0;
45      return (x - x) / (x - x);
46    }
47  if (hx == 0xff800000)
48    {
49      /* x == -Inf.  According to ISO this is NaN.  */
50      *signgamp = 0;
51      return x - x;
52    }
53
54  /* XXX FIXME.  */
55  return __ieee754_expf (__ieee754_lgammaf_r (x, signgamp));
56}
57