gamma(3m)                  DG/UX 4.30                   gamma(3m)



     NAME
          gamma - log gamma function

     SYNOPSIS
          #include <math.h>

          double gamma (x)
          double x;

          extern int signgam;

     DESCRIPTION
          In this discussion, Γ~ represents the Greek letter gamma.

          Gamma returns ln(|Γ~(x)|), where Γ~(x) is defined as
          oo
          ∫ e-ttx-1dt.  The sign of Γ~(x) is returned in the external
          0
          integer signgam.  The argument x must be a non-negative
          integer.

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

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

          LN_MAXDOUBLE is the least value that causes exp(3M) to
          return a range error, and is defined in the <values.h>
          header file.

     DIAGNOSTICS
          For non-negative integer arguments HUGE is returned, and
          errno is set to EDOM.  A message indicating SING error is
          printed on the standard error output.

          If the correct value would overflow, gamma returns HUGE and
          sets errno to ERANGE.

          You can change these error-handling procedures with the
          function matherr(3M).

     SEE ALSO
          exp(3M), matherr(3M), values(5).










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