sclass NLLogicChecker_v3 extends NLLogicChecker_v2 {
  void iterate(Exp e, Matching m, Runnable onMatch) {
    if (e cast Func) {
      if (eq(e.name, "fact")) {
        S pat = nlLogic_text(e.arg);
        for (S fact : facts) {
          LinkedHashMap<S> oldMatches = (LinkedHashMap) cloneMap(m.matches);
          try {
            if (matcher.match(pat, fact, m.matches))
              callF(onMatch);
          } finally {
            m.matches = oldMatches;
          }
        }
      }
    }
  }
}