// visitor: voidfunc(node, parent, parentField)
svoid nlLogic_visitWithParent(IfThen rule, VF3<O, O, S> visitor) {
  if (rule == null) ret;
  callF(visitor, rule);
  nlLogic_visitWithParent(rule.in, rule, 'in, visitor);
  nlLogic_visitWithParent(rule.out, rule, 'out, visitor);
}

svoid nlLogic_visitWithParent(Exp e, O parent, S parentField, VF3<O, O, S> visitor) {
  if (e == null) ret;
  callF(visitor, e, parent, parentField);
  if (e cast And) {
    nlLogic_visitWithParent(e.a, e, 'a, visitor);
    nlLogic_visitWithParent(e.b, e, 'b, visitor);
  } else if (e cast ExpNot)
    nlLogic_visitWithParent(e.a, e, 'a, visitor);
  else if (e cast Func)
    nlLogic_visitWithParent(e.arg, e, 'arg, visitor);
}