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diff --git a/octave_packages/m/specfun/realsqrt.m b/octave_packages/m/specfun/realsqrt.m
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+## Copyright (C) 2008-2012 David Bateman
+##
+## 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} {} realsqrt (@var{x})
+## Return the real-valued square root of each element of @var{x}.  Report an
+## error if any element results in a complex return value.
+## @seealso{sqrt, realpow, reallog}
+## @end deftypefn
+
+function y = realsqrt (x)
+  if (nargin != 1)
+    print_usage ();
+  elseif (iscomplex (x) || any (x(:) < 0))
+    error ("realsqrt: produced complex result");
+  else
+    y = sqrt (x);
+  endif
+endfunction
+
+%!assert (sqrt(1:5),realsqrt(1:5))
+%!test
+%! x = rand (10,10);
+%! assert (sqrt(x),realsqrt(x))
+%!error (realsqrt(-1))