--- a
+++ b/inst/@gf/private/promote_and_check.m
@@ -0,0 +1,45 @@
+## Copyright (C) 2011 David Bateman
+##
+## 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, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn  {Function File} {} promote_and_check (@dots{})
+## Undocumented internal function
+## @end deftypefn
+
+function [varargout] = promote_and_check (varargin)
+  for i = 1 : nargin
+    arg = varargin{i};
+    if (isa (arg, "gf"))
+      m = arg._m;
+      p = arg._prim_poly;
+      break;
+    endif
+  endfor
+  varargout = cell(1, nargout);
+  for i = 1 : nargin
+    arg = varargin{i};
+    if (! isa (arg, "gf"))
+      varargout{i} = gf (arg, m, p);
+    else
+      if (arg._m != m)
+	error ("galois field orders must match");
+      endif
+      if (arg._prim_poly != p)
+	error ("galois field primitive polynomials must match");
+      endif
+      varargout{i} = arg;
+    endif
+  endfor
+endfunction