--- a
+++ b/inst/@gf/sqrt.m
@@ -0,0 +1,30 @@
+## 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} {} sqrt (@var{x})
+## Compute the square-root for each element of @var{x} for a Galois
+## array.
+## @end deftypefn
+
+function y = sqrt (g)
+  tmp = g._index_of(g._x + 1);
+  y = g._alpha_to(floor((tmp + bitand(tmp, 1) * g._n) / 2 + 1));
+endfunction
+
+%!shared g
+%! g = gf([0,2,4,6;1,3,5,7],3);
+%!assert(sqrt(g), gf([0,6,2,4;1,7,3,5],3)
+%!assert(sqrt(g) .* sqrt(g), g)