TraversalPP {
 (@ void selective_visit() {
 // a method using three visitors:
 // SelectiveVisitor: finds objects of some class C (JavaCode)
 // SelectorVisitor:  determines which objects of 
 //   class C should be processed depending on whether
 //   they are contained in some class Y (Before).
 // assumes C-objects are contained in Y-objects.
 // PrintingVisitor: determines how selected objects 
 //   should be processed
 SelectorVisitor sov = new SelectorVisitor(new Boolean(false));  
 SelectiveVisitor siv = new SelectiveVisitor(new PrintingVisitor(), sov);  
 this.all(sov,siv);   
 }
 @)
 (@ void g_print() {
 PrintingVisitor pv = new PrintingVisitor();  
 this.t(pv);   
}
@)
traversal t(PrintingVisitor pv) {to From;}
traversal all(SelectorVisitor sov, SelectiveVisitor siv) { to JavaCode;}
}
JavaCode {
  traversal all_j(PrintingVisitor doingV) { to *;}
}

Main {
(@
static public void main(String args[])
throws Exception {
TraversalPP a = TraversalPP.parse(System.in);
a.selective_visit(); 
a.g_print(); 
System.out.println("  ");  
}
@)
}
SelectiveVisitor{
  after JavaCode (@
    if (soV.get_selected().booleanValue()) {
      host.all_j(doingV);
      soV.set_selected(new Boolean(false));
    }
  @)
}
SelectorVisitor {
  before Before (@ set_selected(new Boolean(true)); @)
}    

PrintingVisitor{

before -> *,*,* (@ System.out.println(" going through edge from " 
  + source.getClass().getName() + " to "
  + dest.getClass().getName() + " labeled "
  + edge); @)

before TraversalPP (@ System.out.println(" traversal-pp  "); @)
after TraversalPP (@ System.out.println("  "); @)
before Body (@ System.out.println(" {  "); @)
after Body (@ System.out.println(" }  "); @)
before Initialize (@ System.out.println(" initialize  "); @)
before Join (@ System.out.println(" join  "); @)
before From (@ System.out.println(" from  "); @)
before To (@ System.out.println(" to  "); @)
before Bypassing (@ System.out.println(" bypassing  "); @)
before Through (@ System.out.println(" through  "); @)
before Edge (@ System.out.println(" ->  "); @)
before Before (@ System.out.println(" before  "); @)
before After (@ System.out.println(" after  "); @)
before ClassName (@ System.out.println
  ("  " + host.get_n() + "   "); @)
before JavaTypeName (@ System.out.println
  ("  " + host.get_name() + "   "); @)
before Variable (@ System.out.println
  ("  " + host.get_name() + "   "); @)
before LabelName (@ System.out.println
  ("  " + host.get_name() + "   "); @)
before FunctionName (@ System.out.println
  ("  " + host.get_name() + "   "); @)
before JavaCode (@ System.out.println
  ("  " + "(" + "@" +  host.get_code() + "@" + ")" + "  "); @)
before Args (@ System.out.println(" (  "); @)
after Args (@ System.out.println(" )  "); @)
before ClassNames (@ System.out.println(" {  "); @)
after ClassNames (@ System.out.println(" }  "); @)
before Traversals (@ System.out.println(" (  "); @)
after Traversals (@ System.out.println(" )  "); @)
   }