math/w_tgamma.c

   1 /* @(#)w_gamma.c 5.1 93/09/24 */
   2 /*
   3  * ====================================================
   4  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   5  *
   6  * Developed at SunPro, a Sun Microsystems, Inc. business.
   7  * Permission to use, copy, modify, and distribute this
   8  * software is freely granted, provided that this notice
   9  * is preserved.
  10  * ====================================================
  11  */
  12
  13 /* double gamma(double x)
  14  * Return  the logarithm of the Gamma function of x or the Gamma function of x,
  15  * depending on the library mode.
  16  */
  17
  18 #include <errno.h>
  19 #include <math.h>
  20 #include <math_private.h>
  21
  22 double
  23 __tgamma(double x)
  24 {
  25         int local_signgam;
  26         double y = __ieee754_gamma_r(x,&local_signgam);
  27
  28         if(__glibc_unlikely (!isfinite (y) || y == 0)
  29            && (isfinite (x) || isinf (x) < 0)
  30            && _LIB_VERSION != _IEEE_) {
  31           if (x == 0.0)
  32             return __kernel_standard(x,x,50); /* tgamma pole */
  33           else if(__floor(x)==x&&x<0.0)
  34             return __kernel_standard(x,x,41); /* tgamma domain */
  35           else if (y == 0)
  36             __set_errno (ERANGE); /* tgamma underflow */
  37           else
  38             return __kernel_standard(x,x,40); /* tgamma overflow */
  39         }
  40         return local_signgam < 0 ? -y : y;
  41 }
  42 weak_alias (__tgamma, tgamma)
  43 #ifdef NO_LONG_DOUBLE
  44 strong_alias (__tgamma, __tgammal)
  45 weak_alias (__tgamma, tgammal)
  46 #endif