/* 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));}