// returns remaining conditions
static Exp nlLogic_checkFirstConditions(NLLogicChecker_v2 c, IfThen rule, NLLogicChecker_v2.Matching m) {
  Exp exp = rule.in;
  while licensed {
    if (exp == null) null;
    Pair<Bool, Exp> p = c.checkFirstCondition(rule, m);
    if (!p.a) ret exp;
    exp = p.b;
  }
}