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
  23 #if LIBM_SVID_COMPAT
  24 double
  25 __tgamma(double x)
  26 {
  27         int local_signgam;
  28         double y = __ieee754_gamma_r(x,&local_signgam);
  29
  30         if(__glibc_unlikely (!isfinite (y) || y == 0)
  31            && (isfinite (x) || (isinf (x) && x < 0.0))
  32            && _LIB_VERSION != _IEEE_) {
  33           if (x == 0.0)
  34             return __kernel_standard(x,x,50); /* tgamma pole */
  35           else if(__floor(x)==x&&x<0.0)
  36             return __kernel_standard(x,x,41); /* tgamma domain */
  37           else if (y == 0)
  38             __set_errno (ERANGE); /* tgamma underflow */
  39           else
  40             return __kernel_standard(x,x,40); /* tgamma overflow */
  41         }
  42         return local_signgam < 0 ? -y : y;
  43 }
  44 weak_alias (__tgamma, tgamma)
  45 # ifdef NO_LONG_DOUBLE
  46 strong_alias (__tgamma, __tgammal)
  47 weak_alias (__tgamma, tgammal)
  48 # endif
  49 #endif