public class Test {

  public static void main(String[] args) {

    Expression e = new AddExp(new IntExp(1), new IntExp(2));

    e.prettyPrint();
    System.out.println("");

    new AddExp(e,e).prettyPrint();
    System.out.println("");

    e.prettyPrint();
    System.out.println(" = " + e.eval());

    e = new AddExp(e,e);
    e.prettyPrint();
    System.out.println(" = " + e.eval());

  }

}