sclass NLLogicChecker_v3 extends NLLogicChecker_v2 {
  void iterate(final Exp e, final Matching m, final Runnable onMatch) {
    if (e cast And)
      iterate(e.a, m, r { iterate(e.b, m, onMatch });

    if (e cast Func) {
      if (eq(e.name, "fact")) {
        S pat = nlLogic_text(e.arg);
        for (S fact : facts) {
          temp tempBackupMatches(m);
          print("matching " + pat + " with " + fact);
          if (matcher.match(pat, fact, m.matches))
            callF(onMatch);
        }
      }
    }
  }
}