gamma(3M)                                                  gamma(3M)


       NAME
             gamma, lgamma - log gamma function

       SYNOPSIS
             cc [flag ...] file ...  -lm [library ...]
             #include <math.h>
             double gamma(double x);
             double lgamma(double x);
             extern int signgam;

       DESCRIPTION
             gamma and lgamma return

                   ln (||~(x)|)

             where |~(x) is defined as

             The sign of |~(x) is returned in the external integer signgam.
             The argument x may not be a non-positive integer.

             The following C program fragment might be used to calculate
             |~:

                   if ((y = gamma(x)) > LN_MAXDOUBLE)
                         error();
                   y = signgam * exp(y);

             where LN_MAXDOUBLE is the least value that causes exp to
             return a range error, and is defined in the values.h header
             file.

          Errors
             For non-positive integer arguments, a value that will compare
             equal to +HUGE_VAL is returned and errno is set to EDOM.  On
             systems that support IEEE exceptions, the divide by zero
             exception is raised.

             If the correct value would overflow, gamma and lgamma return a
             value that will compare equal to +HUGE_VAL and set errno to
             ERANGE.

             On systems that support IEEE NaN, if x is a quiet NaN, that
             value is returned.  If x is a signaling NaN, a quiet NaN is
             returned and the invalid operation exception is raised.  In
             either case, errno is set to EDOM.



                           Copyright 1994 Novell, Inc.               Page 1

      gamma(3M)                                                  gamma(3M)


            If the program was compiled with the -Xt compilation mode, a
            value that will compare equal to HUGE is returned instead of
            HUGE_VAL.  In addition, for non-positive integer arguments, a
            message indicating SING error is printed on the standard error
            output.  These error handling procedures may be changed with
            the function matherr.

      REFERENCES
            cc(1), exp(3M), matherr(3M), values(5)







































                          Copyright 1994 Novell, Inc.               Page 2