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59 lines
2.0 KiB
C
59 lines
2.0 KiB
C
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/* Implementation of gamma function according to ISO C.
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Copyright (C) 1997,1999,2002,2004,2006 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997 and
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Jakub Jelinek <jj@ultra.linux.cz, 1999.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA. */
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#include <math.h>
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#include <math_private.h>
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long double
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__ieee754_gammal_r (long double x, int *signgamp)
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{
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/* We don't have a real gamma implementation now. We'll use lgamma
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and the exp function. But due to the required boundary
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conditions we must check some values separately. */
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int64_t hx;
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u_int64_t lx;
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GET_LDOUBLE_WORDS64 (hx, lx, x);
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if (((hx | lx) & 0x7fffffffffffffffLL) == 0)
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{
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/* Return value for x == 0 is Inf with divide by zero exception. */
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*signgamp = 0;
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return 1.0 / x;
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}
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if (hx < 0 && (u_int64_t) hx < 0xfff0000000000000ULL && __rintl (x) == x)
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{
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/* Return value for integer x < 0 is NaN with invalid exception. */
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*signgamp = 0;
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return (x - x) / (x - x);
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}
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if (hx == 0xfff0000000000000ULL)
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{
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/* x == -Inf. According to ISO this is NaN. */
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*signgamp = 0;
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return x - x;
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}
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/* XXX FIXME. */
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return __ieee754_expl (__ieee754_lgammal_r (x, signgamp));
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}
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