Computes the logarithm of the gamma function.

    This function is supported on OpenVMS Integrity servers and
    Alpha only.

    Format

      #include  <math.h>

      double lgamma  (double x);

      float lgammaf  (float x);

      long double lgammal  (long double x);

1 - Argument

 x

    A real number. x cannot be 0, a negative integer, or Infinity.

2 - Description

    The lgamma functions return the logarithm of the absolute value
    of gamma of x, or ln(|G(x)|), where G is the gamma function.

    The sign of gamma of x is returned in the external integer
    variable signgam. The x argument cannot be 0, a negative integer,
    or Infinity.

3 - Return Values

    x                  The logarithmic gamma of the x argument.
    -HUGE_VAL          The x argument is a negative integer; errno is
                       set to ERANGE.
    NaN                The x argument is NaN; errno is set to EDOM.
    0                  Underflow occurred; errno is set to ERANGE.
    HUGE_VAL           Overflow occurred; errno is set to ERANGE.