AspectJFragment {
{{
  // Find all Variable-objects on the right-hand-side
  // (after the colon) of PointCut-objects
  static String usedVarsSpec =
    "from AspectJFragment via PCExp to Variable";
    // the following strategy is equivalent and more robust
    // "from AspectJFragment via -> *,rhs,* to Variable";
    // This is even better:
    // "from AspectJFragment via PointCut via -> *,rhs,* to Variable";

  // Find all Variable-objects on the left-hand-side
  // (before the colon) of PointCut-objects
  static String definedVarsSpec =
    "from AspectJFragment via ArgDecl to Variable";
    // the following strategy is equivalent and more robust
    // "from AspectJFragment via -> *,lhs,* to Variable";
    // This is even better:
    // "from AspectJFragment via PointCut via -> *,lhs,* to Variable";

  // HashSet implements the Set interface which contains method:
  // add(Object o) 
  // Adds the specified element to this set if 
  // it is not already present.
  HashSet collectVars(String travspec){
    Visitor v = new Visitor(){
      // construct a new empty set
      HashSet return_val = new HashSet();
      void before(Variable v1) {return_val.add(v1);}
      public Object getReturnValue(){return return_val;}
    };
    return (HashSet) Main.cg.traverse(this, travspec, v);
  }
  HashSet getUsedVars() {
    return this.collectVars(usedVarsSpec);
  }
  HashSet getDefinedVars() {
    return this.collectVars(definedVarsSpec);
  }
}}
}