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%
%  This file is part of Logtalk <https://logtalk.org/>
%  SPDX-FileCopyrightText: 2020-2021 Paulo Moura   <pmoura@logtalk.org>
%  SPDX-FileCopyrightText: 2012 Mauro Ferrari      <mauro.ferrari@uninsubria.it>
%  SPDX-FileCopyrightText: 2012 Camillo Fiorentini <fiorenti@dsi.unimi.it>
%  SPDX-FileCopyrightText: 2012 Guido Fiorino      <guido.fiorino@unimib.it>
%  SPDX-License-Identifier: GPL-2.0-or-later
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%  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
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%  (at your option) any later version.
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%  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.
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%  along with this program; if not, write to the Free Software
%  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
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% start by loading the port:

| ?- logtalk_load(fcube(loader)).
...


% to run the port tests:

| ?- logtalk_load(fcube(tester')).
...


% for examples see the tests.lgt file; e.g.:

| ?- ?- fcube::decide((((a & b) => c) <=> ((a => c) | (b => c))), CounterModel).
Input Formula:
F (((a&b) => c) <=> ((a => c) | (b => c)))

Sign Permanence tried,input formula equivalent to: 
   F (((a&b) => c) <=> ((a => c) | (b => c)));
Left branch of F equiv,Main SWFF: F (((a&b) => c) <=> ((a => c) | (b => c)))

      F (((a&b) => c) => ((a => c) | (b => c)));
 
F->,Main SWFF: F (((a&b) => c) => ((a => c) | (b => c)))

         F ((a => c) | (b => c));
         T ((a&b) => c);
 
Main SWFF: F ((a => c) | (b => c))

            F (a => c);
            F (b => c);
            T ((a&b) => c);
 
Main SWFF: T ((a&b) => c)

               T (a => (b => c));
               F (b => c);
               F (a => c);
 
F->,Main SWFF: F (b => c)

                  FC a;
                  FC c;
                  T b;
 
Found a backtacking point:

               F (b => c);
               F (a => c);
               T (a => (b => c));
 
F->,Main SWFF: F (a => c)

                  FC b;
                  FC c;
                  T a;
 
Time: 0.003098999999999963 seconds
 
1 search result = unprovable (fCube-4.1)
*** The Counter Model (see also the prolog term ) ***
-- root --
-- end world -- 
-- end world -- 
         FC a;
         FC c;
         T b;
-- end world -- 
         FC b;
         FC c;
         T a;
-- end world --
*** Prolog term of the countermodel ***
[[[swff(fc,a),swff(fc,c),swff(t,b)],[swff(fc,b),swff(fc,c),swff(t,a)]]]
CounterModel = [[[swff(fc, a), swff(fc, c), swff(t, b)], [swff(fc, b), swff(fc, c), swff(t, a)]]].

