update packages

[CreaPhase.git] / octave_packages / m / specfun / factorial.m

diff --git a/octave_packages/m/specfun/factorial.m b/octave_packages/m/specfun/factorial.m
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+## Copyright (C) 2000-2012 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 3 of the License, 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, see
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} factorial (@var{n})
+## Return the factorial of @var{n} where @var{n} is a positive integer.  If
+## @var{n} is a scalar, this is equivalent to @code{prod (1:@var{n})}.  For
+## vector or matrix arguments, return the factorial of each element in the
+## array.  For non-integers see the generalized factorial function
+## @code{gamma}.
+## @seealso{prod, gamma}
+## @end deftypefn
+
+function x = factorial (n)
+  if (nargin != 1)
+    print_usage ();
+  elseif (any (n(:) < 0 | n(:) != fix (n(:))))
+    error ("factorial: N must all be non-negative integers");
+  endif
+  x = round (gamma (n+1));
+endfunction
+
+%!assert (factorial(5), prod(1:5))
+%!assert (factorial([1,2;3,4]), [1,2;6,24])
+%!assert (factorial(70), exp(sum(log(1:70))), -128*eps)
+%!fail ('factorial(5.5)', "must all be non-negative integers")
+%!fail ('factorial(-3)', "must all be non-negative integers")