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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.
%
% =============================================================================
/*** DEDUCE -- top-level checker command ***/
deduce :-
(
command_arg(expression, EXPRN)
;
prompt_user('DEDUCE -- Type formula to deduce.', 'DEDUCE -- Formula? '),
rread(EXP),
parse_expression(EXP, EXPRN)
),
(
EXPRN=c#N,
conc(N,FORMULA)
;
novars(EXPRN), /* CFR009 */
checktype(EXPRN, boolean), /* CFR009 */
FORMULA=EXPRN
),
(
command_arg(hyplist, HYPLIST)
;
prompt_user('Hypotheses to be used? '),
rread(HYPLIST),
check_hyplist(HYPLIST)
),
build_formula(FORMULA, HYPLIST, F1),
(
try_deduce(F1),
!,
write('*** '),
print(F1),
nl,
write('*** '),
print(FORMULA),
write(' by logical deduction'),
nl,
add_new_hyp(FORMULA,1)
;
!,
write('*** FAILED'),
nl,
fail
),
(
EXPRN=c#N,
done(N)
;
true
), !.
/*** BUILD_FORMULA(C,HYPS,F) - create a "HYPS -> C" formula, F ***/
build_formula(F,[],F) :-
!.
build_formula(F,[N],X -> F) :-
!,
hyp(N,X), !.
build_formula(F,[N|T],(H and Y) -> F) :-
build_formula(F,T,Y -> F),
hyp(N,H), !.
/*** TRY_DEDUCE(F) - deduce formula F by truth-table means if possible ***/
try_deduce(F) :-
var_in(F,V),
!,
subst_vbl(V,false,F,F1),
try_deduce(F1),
subst_vbl(V,true,F,F2),
try_deduce(F2), !.
try_deduce(F) :-
simplify(F,true), !.
/*** VAR_IN(FORM,ATF) - find an atf ATF in formula FORM if possible ***/
var_in(not F,V) :- var_in(F,V).
var_in(X and Y,V) :- (var_in(X,V) ; var_in(Y,V)).
var_in(X or Y,V) :- (var_in(X,V) ; var_in(Y,V)).
var_in(X -> Y,V) :- (var_in(X,V) ; var_in(Y,V)).
var_in(X <-> Y,V) :- (var_in(X,V) ; var_in(Y,V)).
var_in(V,V) :- logic_free(V), V\=true, V\=false.
/*** LOGIC_FREE(F) - succeeds if no connectives in F, i.e. if F is an atf ***/
logic_free(not _) :- !, fail.
logic_free(_ or _) :- !, fail.
logic_free(_ and _) :- !, fail.
logic_free(_ -> _) :- !, fail.
logic_free(_ <-> _) :- !, fail.
logic_free(_).
/*** SUBST_VBL(V,X,OLD,NEW) - substitute all V in OLD by X to get NEW ***/
subst_vbl(V,X,V,X) :- !.
subst_vbl(_V,_X,Y,Y) :-
atomic(Y),
!.
subst_vbl(V,X,F,F1) :-
F=..[OP|Args],
subst_vbl_list(V,X,Args,Args1),
F1=..[OP|Args1],
!.
/*** SUBST_VBL_LIST(V,X,OL,NL) - substitute all V in OL by X to get NL ***/
subst_vbl_list(V,X,[A],[A1]) :- subst_vbl(V,X,A,A1), !.
subst_vbl_list(V,X,[A|Args],[A1|Args1]) :-
subst_vbl(V,X,A,A1),
!,
subst_vbl_list(V,X,Args,Args1),
!.
%###############################################################################
%END-OF-FILE
|
