//checks for unique parts.
//
// Collaboration
// role System played by Grammar
//   out  void checkUnique(final ClassGraph cg)
//   in   Strategy getAllUnitsToBeChecked
// role UnitToBeChecked played by Statement
//   in   Strategy checkAllParts 
// role NotDuplicated played by NonTerminal

// System = List(UnitToBeChecked).
// UnitToBeChecked = List(NotDuplicated).
// NotDuplicated = Ident.           

Grammar{
{{
  Strategy getAllUnitsToBeChecked = new Strategy("from Grammar to Statement");
  void checkUnique(final ClassGraph cg){
  	cg.traverse(this, getAllUnitsToBeChecked, new Visitor(){
  		void before(Statement a){
  			a.checkDuplicateParts(cg);
		}
	});
  }
}}
}

Statement{
{{
  Strategy checkAllParts = new Strategy(
    "from Statement through Expression to NonTerminal");
  void checkDuplicateParts(ClassGraph cg){
  	cg.traverse(this, checkAllParts, new Visitor(){
    	        HashSet hParts = new HashSet();
		void before(NonTerminal l){
		  if(!hParts.add(l.get_ident())){
			System.out.println("Element "+
			l.get_ident() + " is not unique."); 
		  }
		}
	});
  }
}}
}