gamma(3M)                        DG/UX 5.4.2                       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(|Γ~(x)|)

       where Γ~(x) is defined as

              integral from 0 to oo of e^(-t)t^(x-1)dt

       The sign of Γ~(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 Γ~:

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

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

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

DIAGNOSTICS
       For non-positive 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 and lgamma return HUGE and
       set errno to ERANGE.

       Except when the -Xc compilation option is used, these error-handling
       procedures may be changed with the function matherr.  When the -Xa or
       -Xc compilation options are used, HUGEVAL is returned instead of
       HUGE and no error messages are printed.







Licensed material--property of copyright holder(s)                         1