new file mode 100644
--- /dev/null
+++ b/scripts/set/private/validargs.m
@@ -0,0 +1,57 @@
+## Copyright (C) 2000, 2005, 2006, 2007, 2008, 2009 Paul Kienzle
+## Copyright (C) 2009, 2010 Jaroslav Hajek
+##
+## 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/>.
+
+## Validate arguments for binary set operation.
+function [x, y] = validargs (caller, x, y, byrows_arg)
+
+  if (nargin == 3)
+    icx = iscellstr (x);
+    icy = iscellstr (y);
+    if (icx || icy)
+      if (icx && ischar (y))
+        y = cellstr (y);
+      elseif (icy && ischar (x))
+        x = cellstr (x);
+      elseif (! (icx && icy))
+        error ("%s: cell array of strings cannot be combined with a nonstring value", caller);
+      endif
+    elseif (! (ismatrix (x) && ismatrix (y)))
+      error ("%s: input arguments must be arrays or cell arrays of strings", caller); 
+    endif
+  elseif (nargin == 4)
+    if (strcmpi (byrows_arg, "rows"))
+      if (iscell (x) || iscell (y))
+        error ("%s: cells not supported with ""rows""");
+      elseif (! (ismatrix (x) && ismatrix (y)))
+        error ("%s: input arguments must be arrays or cell arrays of strings", caller); 
+      else
+        if (ndims (x) > 2 || ndims (y) > 2)
+          error ("%s: need 2-dimensional matrices for ""rows""", caller);
+        elseif (columns (x) != columns (y) && ! (isempty (x) || isempty (y)))
+          error ("%s: number of columns must match", caller);
+        endif
+      endif
+    else
+      error ("%s: invalid option: %s", caller, byrows_arg);
+    endif
+  else
+    print_usage (caller);
+  endif
+
+endfunction