math/w_tgamma_compat.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 #include <math-svid-compat.h>
  22 #include <libm-alias-double.h>
  23
  24 #if LIBM_SVID_COMPAT
  25 double
  26 __tgamma(double x)
  27 {
  28         int local_signgam;
  29         double y = __ieee754_gamma_r(x,&local_signgam);
  30
  31         if(__glibc_unlikely (!isfinite (y) || y == 0)
  32            && (isfinite (x) || (isinf (x) && x < 0.0))
  33            && _LIB_VERSION != _IEEE_) {
  34           if (x == 0.0)
  35             return __kernel_standard(x,x,50); /* tgamma pole */
  36           else if(__floor(x)==x&&x<0.0)
  37             return __kernel_standard(x,x,41); /* tgamma domain */
  38           else if (y == 0)
  39             __set_errno (ERANGE); /* tgamma underflow */
  40           else
  41             return __kernel_standard(x,x,40); /* tgamma overflow */
  42         }
  43         return local_signgam < 0 ? -y : y;
  44 }
  45 libm_alias_double (__tgamma, tgamma)
  46 #endif