learn(Predicate, VarsIndex, Rules) :-
  collect_objects(Objects),
  findall(pos(Args), (known_fact(Fact), Fact =.. [Predicate|Args]), PosExamples),
  gen_neg_examples(Objects, PosExamples, VarsIndex, NegExamples),
  write_ln(PosExamples),
  write_ln(NegExamples),
  learn_rules(PosExamples, NegExamples, Predicate, VarsIndex, Rules).


collect_objects(Objects) :-
  findall(Args, (known_fact(Fact), Fact =.. [_|Args]), ArgList),
  conc_lists(ArgList, RawArgList),
  setof(X, member(X, RawArgList), Objects).

conc_lists([], []).

conc_lists([First | Rest], RawList) :-
  append(First, Result, RawList),
  conc_lists(Rest, Result).

gen_neg_examples(Objects, PosExamples, N, NegExamples) :-
  findall(P, permute(Objects, N, P), Permutations),
  extract_args(PosExamples, PosList),
  build_neg_examples(Permutations, PosList, NegExamples).

permute(_, 0, []).

permute(Objects, N, [X | Result]) :-
  M is N - 1,
  member(X, Objects),
  delete(Objects, X, RestObjects),
  permute(RestObjects, M, Result).

extract_args([], []).

extract_args([Example | RestExamples], [Args | Result]) :-
  Example =.. [_ | Args],
  extract_args(RestExamples, Result).

build_neg_examples([], _, []).

build_neg_examples(
    [Permutation | RestPermutations],
    PosList,
    [Out | Result]) :-
  not(member(Permutation, PosList)),
  Out =.. [neg | Permutation],
  build_neg_examples(RestPermutations, PosList, Result).

build_neg_examples(
    [Permutation | RestPermutations],
    PosList,
    Result) :-
  member(Permutation, PosList),
  build_neg_examples(RestPermutations, PosList, Result).