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% -----------------------------------------------------------------------------
% (C) Altran Praxis Limited
% -----------------------------------------------------------------------------
%
% The SPARK toolset is free software; you can redistribute it and/or modify it
% under terms of the GNU General Public License as published by the Free
% Software Foundation; either version 3, or (at your option) any later
% version. The SPARK toolset 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 distributed with the SPARK toolset; see file
% COPYING3. If not, go to http://www.gnu.org/licenses for a complete copy of
% the license.
%
% =============================================================================
/*** CONTRADICT(FORMULA_OR_CONC_NUM) -- proof by contradiction ***/
contradict(F) :-
(
F=c#N,
integer(N),
conc(N,FORMULA)
;
checktype(F,boolean),
FORMULA=F
),
write('ENTERING PROOF BY CONTRADICTION ATTEMPT'),
nl,
start_subgoal(FORMULA,[false],(not FORMULA),'CONTRADICTION'),
!.
/*** IMPLICATION(FORMULA_OR_CONC_NUM) -- proof by implication ***/
implication(F) :-
(
F=c#N,
integer(N),
conc(N,FORMULA)
;
checktype(F,boolean),
FORMULA=F
),
FORMULA=(ASSUMPTIONS -> GOAL),
create_formula(GOALS,false,GOAL -> false),
write('ENTERING PROOF BY IMPLICATION ATTEMPT'),
nl,
start_subgoal(FORMULA,GOALS,ASSUMPTIONS,'IMPLICATION'),
!.
%###############################################################################
%END-OF-FILE
|
