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authorUlrich Drepper <drepper@redhat.com>1999-07-14 00:54:57 +0000
committerUlrich Drepper <drepper@redhat.com>1999-07-14 00:54:57 +0000
commitabfbdde177c3a7155070dda1b2cdc8292054cc26 (patch)
treee021306b596381fbf8311d2b7eb294e918ff17c8 /sysdeps/ieee754/ldbl-96/e_gammal_r.c
parent86421aa57ecfd70963ae66848bd6a6dd3b8e0fe6 (diff)
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+/* Implementation of gamma function according to ISO C.
+   Copyright (C) 1997, 1999 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 Library General Public License as
+   published by the Free Software Foundation; either version 2 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
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  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>
+
+
+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 (((es & 0x7fff) | hx | lx) == 0)
+    {
+      /* Return value for x == 0 is NaN with invalid exception.  */
+      *signgamp = 0;
+      return x / x;
+    }
+  if ((hx & 0x8000) != 0 && (hx & 0x7fff) != 0x7fff && __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));
+}