PFDS Unbalanced Tree Set implementation

pfds_unbalanced_tree_set.scala

class UnbalancedTreeSet[T] private (tree: BinaryTree[T]) (implicit val ordering: Ordering[T])
  extends Set[T] {

  def this()(implicit ordering : Ordering[T]) = this(BinaryTreeLeaf)(ordering)
  private def newSet(tree: BinaryTree[T]) = new UnbalancedTreeSet[T](tree);

  def insert(x: T) = newSet(UnbalancedTreeSet.insert(x, tree))
  def member(x: T) = UnbalancedTreeSet.member(x, tree)
}