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+## Copyright (C) 2011 John W. Eaton
+##
+## 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} {} addpref (@var{group}, @var{pref}, @var{val})
+## Add a preference @var{pref} and associated value @var{val} to the
+## named preference group @var{group}.
+##
+## The named preference group must be a character string.
+##
+## The preference @var{pref} may be a character string or a cell array
+## of character strings.  The corresponding value @var{val} may be any
+## value, or, if @var{pref} is a cell array of strings, @var{val}
+## must be a cell array of values with the same size as @var{pref}.
+## @seealso{pref, getpref, ispref, rmpref, setpref}
+## @end deftypefn
+
+## Author: jwe
+
+function addpref (group, pref, val)
+
+  if (nargin == 3)
+    if (ischar (group))
+      prefs = loadprefs ();
+      if (ischar (pref))
+        if (isfield (group, pref))
+          error ("preference %s already exists in group %s", pref, group);
+        else
+          prefs.(group).(pref) = val;
+        endif
+      elseif (iscellstr (pref))
+        if (size_equal (pref, val))
+          for i = 1:numel(pref)
+            if (isfield (group, pref{i}))
+              error ("preference %s already exists in group %s",
+                     pref{i}, group);
+            else
+              prefs.(group).(pref{i}) = val;
+            endif
+          endfor
+        else
+          error ("size mismatch for pref and val");
+        endif
+      else
+        error ("expecting pref to be a character string or cellstr");
+      endif
+      saveprefs (prefs);
+    else
+      error ("expecting group to be a character string");
+    endif
+  else
+    print_usage ();
+  endif
+
+endfunction
+
+%% Testing these functions will require some care to avoid wiping out
+%% existing (or creating unwanted) preferences for the user running the
+%% tests.