||Tag "author" with body "@author Jaco van Kooten
Original author was Jaco van Kooten. Ported to PHP by Paul Meagher.
The natural logarithm of the gamma function. <br />
Based on public domain NETLIB (Fortran) code by W. J. Cody and L. Stoltz <br />
Applied Mathematics Division <br />
Argonne National Laboratory <br />
Argonne, IL 60439 <br />
<li>W. J. Cody and K. E. Hillstrom, 'Chebyshev Approximations for the Natural
Logarithm of the Gamma Function,' Math. Comp. 21, 1967, pp. 198-203.</li>
<li>K. E. Hillstrom, ANL/AMD Program ANLC366S, DGAMMA/DLGAMA, May, 1969.</li>
<li>Hart, Et. Al., Computer Approximations, Wiley and sons, New York, 1968.</li>
From the original documentation:
This routine calculates the LOG(GAMMA) function for a positive real argument X.
Computation is based on an algorithm outlined in references 1 and 2.
The program uses rational functions that theoretically approximate LOG(GAMMA)
to at least 18 significant decimal digits. The approximation for X > 12 is from
reference 3, while approximations for X < 12.0 are similar to those in reference
1, but are unpublished. The accuracy achieved depends on the arithmetic system,
the compiler, the intrinsic functions, and proper selection of the
Error returns: <br />
The program returns the value XINF for X .LE. 0.0 or when overflow would occur.
The computation is believed to be free of underflow and overflow.
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