class IntSet11b extends IntSet11
{
// Adds a copy to sets implemented using linked lists
// Copy method uses recursion

 public IntSet11b()
 {
  super();
 }

 private IntSet11b(Cell l)
 {
  list=l;
 }
 
 public IntSet11b copy()
 {
  return new IntSet11b(copy(list));
 }

 private static Cell copy(Cell l)
 {
  if(l==null)
     return null;
  else
     return new Cell(l.first,copy(l.next));
 }
}