c$Header: /weru/cvs/weps/weps.src/util/math/factln.for,v 1.2 1999-04-26 20:20:30 wagner Exp $
c
      real function factln
     i                 (n)
c
c     + + + PURPOSE + + +
c     Computes the ln(n!) for n > 0
c
c     Based on:
c     'NUMERICAL RECIPES - The Art of Scientific Computing',
c     W.H. Press, B.P. Flannery, S.A. Teukolsky, W.T. Vetterling
c     Cambridge University Press, 1986
c     pg 159
c
c     + + + KEYWORDS + + +
c     factorial
c
c     + + + ARGUMENT DECLARATIONS + + +
      integer n
c
c
c     + + + ARGUMENT DEFINITIONS + + +
c     n      - real value for values >= 0
c
c     + + + LOCAL VARIABLES + + +
c
      real   gammln
      real   a(100)
c
      data a / 100*-1 /
c
c     + + + END SPECIFICATIONS + + +
c
      if (n .lt. 0) then
          write (*,*) 'In function factln(n): negative factorial!!'
      endif
      if (n .le. 99) then
          if (a(n+1) .lt. 0.0) a(n+1) = gammln(n+1.0)
          factln = a(n+1)
      else
          factln = gammln(n+1.0)
      endif

      return
      end