prove(Fact):-
	if_then(Conditions,Fact),
	infer_each(Conditions).
prove(Fact):-
	ask(Fact).

infer_each([]).
infer_each([Fact|Rest]):-
	prove(Fact),
	infer_each(Rest).

ask(Fact):-
	write('Is it true that '), write(Fact), write('?'), nl,
	read(Ans),
	Ans=yes.

run:-
	retractall(if_then(_,_)),
	write('Select a knowledge base ...'),
	read(KB),
	load_files([KB], [compilation_mode(assert_all)]),
	write('Type in a goal ...'),
	read(Goal),
	prove(Goal),
	write('Proved!'), nl, !.

run:-
	write('Not proved!'), nl.