// The list-based set, with ordering
public class SetBB extends LBS implements OrderedSet {

   public SetBB() {  super(); }

   // positions the list at where element x should be
   // returns null if it's not htere.
   private ListOfObjects locate(OrderableElement x) {
      ls.reset();
      while (!ls.atEnd()) {
         OrderableElement curr = (OrderableElement) ls.getItem();
         if (curr.elEquals(x))return ls;
         if (curr.elGreaterThan(x)) return null;
         ls.next();
      }
      return null;
   }

   public Element find(OrderableElement x) {
      if (locate(x) == null) return null;
      else return (Element)ls.getItem();
   }

   public void insert(OrderableElement x) {
      if (locate(x) == null) ls.insert(x);
   }

   public void delete(OrderableElement x) {
      if (locate(x) != null) ls.delete();
   }

   public boolean hasElement(OrderableElement x) {
      return locate(x) != null;
   }

   public void union(OrderedSet other) {
      if (this != other) {
         Element[] elems = other.getContents();
         for (int i=0; i < elems.length; ++i) {
            insert((OrderableElement) elems[i]);
         }
      }
   }
   public void intersection(OrderedSet other) {
      if (this != other) {
         Element[] elems = getContents();
         for (int i=0; i < elems.length; ++i) {
            if (!other.hasElement((OrderableElement) elems[i])) 
               delete((OrderableElement) elems[i]);
         }
      }
   }
   public void difference(OrderedSet other) {
      if (this != other) {
         Element[] elems = other.getContents();
         for (int i=0; i < elems.length; ++i) {
            delete((OrderableElement) elems[i]);
         }
      }
   }

   public String toString() { return "Set " + ls; }
   
}