C+
C NAME:
C	GAMMALN
C PURPOSE:
C	Calculate natural logarithm of gamma function for X>1
C CATEGORY:
C	Math: special functions
C CALLING SEQUENCE:
	function GAMMALN(XX)
C INPUTS:
C	XX	real*4	(read-only)	x-value where gamma fnc is evaluated
C OUTPUTS:
C	GAMMALN real*4	logarithm of gamma function in X
C SIDE EFFECTS:
C RESTRICTIONS:
C PROCEDURE:
C	Lanczos formulae. Calculations are performed in double precision.
C MODIFICATION HISTORY:
C	Numerical Recipes, p. 157.
C-
	    real		XX

	double precision	COF(6)	/76.18009173d0,-86.50532033d0,24.01409822d0,
     &				  -1.231739516d0,.120858003d-2,-.536382d-5/
	double precision	STP	/2.50662827465d0/
	double precision	HALF	/0.5d0/
	double precision	ONE	/1.0d0/
	double precision	FPF	/5.5d0/
	double precision	X
	double precision	TMP
	double precision	SER

	X   = XX-ONE
	TMP = X+FPF
	TMP = (X+HALF)*LOG(TMP)-TMP
	SER = ONE
	do J=1,6
	    X   = X+ONE
	    SER = SER+COF(J)/X
	end do
	GAMMALN = TMP+log(STP*SER)

	return
	end