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yap-6.3/Logtalk/examples/lpa/fault.lgt

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:- object(fault,
imports(proto_hierarchy)).
:- info([
author is 'Paulo Moura',
version is 1.0,
date is 2000/4/22,
comment is 'Expert system for automobile fault diagnosis.',
source is 'Example adopted from the LPA Prolog++ documentation.']).
:- public(findall/0).
:- mode(findall, one).
:- private(told_by_user_/2).
:- dynamic(told_by_user_/2).
:- mode(told_by_user_(?nonvar, ?nonvar), zero_or_more).
:- public(find/1).
:- mode(find(?nonvar), zero_or_more).
:- private(exhibited/1).
:- mode(exhibited(+nonvar), zero_or_one).
:- public(contrary/2).
:- mode(contrary(?nonvar, ?nonvar), zero_or_more).
:- public(fault/2).
:- mode(fault(?nonvar, ?nonvar), zero_or_more).
:- public(effect/2).
:- mode(effect(?nonvar, ?nonvar), zero_or_more).
:- public(symptom/2).
:- mode(symptom(?nonvar, ?nonvar), zero_or_more).
findall :-
retractall(told_by_user_(_, _)),
write('Please answer all questions with yes or no.'), nl, nl,
forall(
(::descendant(Where), Where::find(Description)),
(nl, write('Location : '), write(Where), nl,
write('Possible Fault: '), write(Description), nl)),
nl, write('No (more) explanations found.').
find(Description) :-
::fault(Fault, Description),
forall(::effect(Fault, Symptom), exhibited(Symptom)).
exhibited(Symptom) :-
told_by_user_(Symptom, Reply),
!,
Reply = yes.
exhibited(Symptom) :-
::symptom(Symptom, Description),
write(Description), write('? '),
read(Reply),
asserta(told_by_user_(Symptom, Reply)),
Reply = yes,
forall(
(::contrary(Symptom, Contrary);
::contrary(Contrary, Symptom)),
asserta(told_by_user_(Contrary, no))).
:- end_object.