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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.
%
% =============================================================================
/*** SIMPLIFY -- top-level checker command ***/
simplify :-
movenots ;
split_hyps ;
split_concs ;
do_implication ;
equivalence.
simplify :- !.
/*** MOVENOTS - move nots as far into expressions as possible ***/
movenots:-
retractall(hn(_)),
assertz(hn(1)),
repeat,
hn(N),
(
gethyp(N,H),
negin(H,H1),
assertz(hyp(N,H1)),
(
H1=H
;
H1\=H,
assertz(logfact(newhyp, hyp(N,H1))),
new_hyp_message(N, H1) /* CFR018 */
)
;
hn(N)
),
M is N+1,
retract(hn(N)),
assertz(hn(M)),
bigger_than_all_hyps(M),
!,
fail.
bigger_than_all_hyps(M) :-
hyp(N,_),
N>=M,
!,
fail.
bigger_than_all_hyps(_) :- !.
/*** GETHYP(N,H) - instantiates H to the Nth hypothesis & retracts it ***/
gethyp(N,H) :-
hyp(N,H),
retract(hyp(N,H)), !.
/*** SPLIT_HYPS - split conjunction hypotheses into two or more hypotheses ***/
split_hyps :-
retract(hyp(_N,A and B)),
add_new_hyp(A,1),
add_new_hyp(B,1),
!,
split_hyps.
/*** SPLIT_CONCS - split conjunction conclusions into separate conclusions ***/
split_concs :-
retract(conc(_N,A and B)),
add_new_conc(A,1),
add_new_conc(B,1),
!,
split_concs.
/*** DO_IMPLICATION - given "A" and "A -> B", add "B" as a hypothesis; given
"not B" and "A -> B", add "not A" as a hypothesis ***/
/*** ADDED 4/3/85 -- needs improvement for generality ***/
do_implication :-
hyp(_,A -> B),
hyp(_,A),
add_new_hyp(B,1),
fail.
do_implication :-
hyp(_,A -> B),
hyp(_,(not B)),
negin((not A),C),
add_new_hyp(C,1),
fail.
/*** EQUIVALENCE - given "A" and "A <-> B" or "B <-> A", add "B";
given "not A" and "A <-> B" or "B <-> A", add "not B" ***/
equivalence :-
hyp(_,A <-> B),
hyp(_,A),
add_new_hyp(B,1),
fail.
equivalence :-
hyp(_,A <-> B),
hyp(_,B),
add_new_hyp(A,1),
fail.
equivalence :-
hyp(_,A <-> B),
hyp(_,not(A)),
negin(not(B),C),
add_new_hyp(C,1),
fail.
equivalence :-
hyp(_,A <-> B),
hyp(_,not(B)),
negin(not(A),C),
add_new_hyp(C,1),
fail.
%###############################################################################
%END-OF-FILE
|
