gamma(3)                            CLIX                            gamma(3)



  NAME

    gamma - Log gamma function

  LIBRARY

    Standard Math Library (libm.a)

    Intergraph Math Library (libmath.a)

  SYNOPSIS

    #include <math.h>

    double gamma(
      double x );

    extern int signgam(
      void );

  PARAMETERS

    x   An argument of type double

  DESCRIPTION

    T
oh
oe gamma() function returns ln(|Γ~(x)|) where Γ~(x) is defined as
    ∫ e-ttx-1dt.  The sign of Γ~(x) is returned in the external integer
    0
signgam.  The argument x may not be a nonpositive integer.

  EXAMPLES

    The following calculates Γ~:

    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.

  RETURN VALUES

    For non-negative integer arguments HUGE is returned, and errno is set to
    EDOM.  A message indicating SING error is displayed on stderr.

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

    These error-handling procedures may be changed with the function
    matherr().



  2/94 - Intergraph Corporation                                              1

  gamma(3)                            CLIX                            gamma(3)



  RELATED INFORMATION

    Functions:  exp(3), matherr(3)

    Miscellany:  values(0)

















































  2                                              Intergraph Corporation - 2/94