Main {
{{
  static ClassGraph cg;
  public static void main(String args[]) throws Exception {
    Exps es = Exps.parse(System.in);
    ClassGraph g = new ClassGraph(true,false);
    cg = new ClassGraph(true, false);
    cg = new ClassGraph(cg,
	    "from Exps bypassing -> *,tail,* to *");
    cg.traverse(es,"from Exps to Simple", new Visitor() {
    // cg.traverse(es,"from Exps to-stop Exp", new Visitor() {
      public void start() {System.out.println("Testing the evaluator");};
      public void before(Exp host){
	host.print();
        System.out.println(" new Exp ========================= ");
	List l = host.eval();
        for(Iterator i = l.iterator(); i.hasNext();) {
          System.out.print(" ClassName ");
          ((ClassName)i.next()).print();
          System.out.println();
	};
      }
      public void before(Equation host){
        System.out.println(" start of Equation-object +++++++++++++ ");
      } ;});
    cg.traverse(es,"from Exps via Sequential to ClassName", new Visitor() {
      public void start() {System.out.println("start with ClassName printing");};
      public void before(ClassName host){
	host.print(); System.out.println();
      }
      public void finish() {System.out.println("done with ClassName printing");};
    });
    TraversalGraph tg = new TraversalGraph("from Exps via Sequential to ClassName", cg);
    System.out.println("TraversalGraph");
    System.out.println();
    System.out.println(tg);
    cg.traverse(es,"from Exps to {Forward, Backward}", new Visitor() {
      public void before(Forward host){
	if (host.steps == null) host.set_steps(new Unlimited());
      }
      public void before(Backward host){
	if (host.steps == null) host.set_steps(new Unlimited());
      }
    });
    System.out.println(" modified Exps-object ");
    es.print();
    System.out.println();
    System.out.println(" displayed object ");
    es.display();
    System.out.println(" done ");
  }
}}
}

ClassName {
  void print() to * (PrintVisitor);
}

Exp {
  void print() to * (PrintVisitor);
}

Exps {
  void print() to * (PrintVisitor);
  void display() to * (DisplayVisitor);
}

Exp {
{{
  abstract List eval();
}}
}

Simple {
{{
  abstract List eval();
}}
}

Forward {
{{
  List eval(){ ArrayList t = new ArrayList();
    t.add(source); return t;
  };
}}
}

Backward {
{{
  List eval(){ ArrayList t = new ArrayList();
    t.add(source); t.add(target); return t;
  };
}}
}

Sequential {
{{
  List eval(){ return new ArrayList();};
}}
}

Later {
{{
  List eval(){ ArrayList t = new ArrayList();
    t.add(source); t.add(target); return t;
  };
}}
}

UpOverDown {
{{
  List eval(){ ArrayList t = new ArrayList();
    t.add(target); return t;
  };
}}
}

Exists {
{{
  List eval(){ return new ArrayList();};
}}
}


Op {
{{
  abstract List apply(List t);
}}
}

Union {
{{
  List apply(List args){
    List r = new ArrayList();
    for(Iterator i = args.iterator(); i.hasNext();)
      r.addAll((List)i.next());
      return r;
  }
}}
}

Join {
{{
  List apply(List args){
    List r = new ArrayList();
    for(Iterator i = args.iterator(); i.hasNext();)
      r.addAll((List)i.next());
      return r;
  }
}}
}


Compound {
{{
  List eval(){
	List t = new ArrayList();
	for(Enumeration e = args.elements();e.hasMoreElements();)
  	  t.add(((Exp)e.nextElement()).eval());
        return op.apply(t);
  }
}}
}