class List {
  def isEmpty(): Int = this.isEmpty();
  def head() : Int = this.head();
  def tail() : List = this.tail();
  def cons(x: Int): List = new Cons(x,this);
  def print() {
    if(this.isEmpty()) printChar(10);
    else {
      printInt(this.head());
      do this.tail().print();
    }
  }
}

class Cons extends List {
  val head : Int;
  val tail : List;
  def isEmpty(): Int = false;
  def head() : Int = this.head;
  def tail() : List = this.tail;
}

class Nil extends List {
  def isEmpty(): Int = true;
}

{
  var l : List = new Nil();
  set l = l.cons(1);
  set l = l.cons(2);
  do l.print();
}