--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/specfun/factorial.m	Wed May 17 21:00:54 2006 +0000
@@ -0,0 +1,39 @@
+## Copyright (C) 2000 Paul Kienzle
+##
+## This file is part of Octave.
+##
+## Octave 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, or (at your option)
+## any later version.
+##
+## Octave 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 Octave; see the file COPYING.  If not, write to the Free
+## Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+## 02110-1301, USA.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} factorial (@var{n})
+## Return the factorial of @var{n}. If @var{n} is scalar, this is
+## equivalent to @code{prod (1:@var{n})}.  If @var{n} is an array,
+## the factorial of the elements of the array are returned.
+## @end deftypefn
+
+function x = factorial (n)
+  if (any (n(:) < 0))
+    error ("factorial: n be be a scalar or array 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