// Check for undefined classes 


Cd_graph {
{{
	//Need to keep track of what classes are defined correctly

	HashSet definedClasses = new HashSet();
 	
      // Function which traverses the cg, records defined classes in hashset

	public void check_undefined(ClassGraph cg) {
		// Strategy bypasses Construct_ns 
		Strategy sg = new Strategy("from Cd_graph bypassing Construct_ns to Vertex");
    		TraversalGraph tg = new TraversalGraph(sg,cg);
    
    		
    
		tg.traverse(this, new Visitor() {
 			HashSet hclasses;

	      	// First build hashset
			public void start() {
				hclasses = new HashSet();
			}
      
			public void before(Vertex host) { 
        			Ident cname = host.get_vertex_name();
        			hclasses.add(cname);
      		}
			
			// Need to return the hashset after traversal
      		public Object getReturnValue() {
				return hclasses;
			} 
		
		 }); //end of traversal

        
    // See if classes are defined in the hashset

    Strategy sg2 = new Strategy("from Cd_graph through Construct_ns to Vertex");
    TraversalGraph tg2 = new TraversalGraph(sg2,cg);
    
    tg2.traverse( this, new Visitor() {
    	  public void before(Vertex host){ 
        	Ident cname = host.get_vertex_name();
        	if(!definedClasses.contains(cname)) {
          		System.err.println(" ERROR: Class " + cname + " is not defined. "); 
        	}
        } 
    }); //end of traversal
  } //end of check_undefined
}}
}