## Copyright (C) 2000 Paul Kienzle
##
## This program is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this program; if not, write to the Free Software
## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

## factorial(n)
##   ==prod(1:n)
function x = factorial(n)
  if (any (n (:) < 0))
    error ("factorial: n be be a scalar or matrix of positive integers");
  endif
  if (isscalar (n))
    x = prod(2:n);
  else
    n (find (n < 1)) = 1;
    m = max(n(:));
    c = cumprod(1:m);
    x = c(floor(n));
  endif
endfunction