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