path: root/src/library/scala/collection/immutable/TreeSet.scala

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2009, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

// $Id$


package scala.collection.immutable

import generic._

/** The canonical factory of <a href="TreeSet.html">TreeSet</a>'s. */
object TreeSet {

  type Coll = TreeSet[_]
  implicit def implicitBuilder[A <% Ordered[A]]: Builder[A, TreeSet[A]] = newBuilder[A]
  def newBuilder[A <% Ordered[A]]: Builder[A, TreeSet[A]] = new AddingBuilder(empty[A])

  /** The empty set of this type
   */
  def empty[A <% Ordered[A]] = new TreeSet[A]

  /** The canonical factory for this type
   */
  def apply[A <% Ordered[A]](elems: A*) : TreeSet[A] = empty[A] ++ elems
}

/** This class implements immutable sets using a tree.
 *
 *  @author  Martin Odersky
 *  @version 2.0, 02/01/2007
 */

@serializable
class TreeSet[A <% Ordered[A]](override val size: Int, t: RedBlack[A]#Tree[Unit])
  extends RedBlack[A] with SortedSet[A] with SortedSetTemplate[A, TreeSet[A]] {

  def isSmaller(x: A, y: A) = x < y

  def this() = this(0, null)

  protected val tree: RedBlack[A]#Tree[Unit] = if (size == 0) Empty else t

  private def newSet(s: Int, t: RedBlack[A]#Tree[Unit]) = new TreeSet[A](s, t)

  /** A factory to create empty sets of the same type of keys.
   */
  override def empty = TreeSet.empty

  /** A new TreeSet with the entry added is returned,
   */
  def + (elem: A): TreeSet[A] = {
    val newsize = if (tree.lookup(elem).isEmpty) size + 1 else size
    newSet(newsize, tree.update(elem, ()))
  }

  /** A new TreeSet with the entry added is returned,
   *  assuming that elem is <em>not</em> in the TreeSet.
   */
  def insert (elem: A): TreeSet[A] = {
    assert(tree.lookup(elem).isEmpty)
    newSet(size + 1, tree.update(elem, ()))
  }

  def - (elem:A): TreeSet[A] =
    if (tree.lookup(elem).isEmpty) this
    else newSet(size - 1, tree.delete(elem))

  /** Checks if this set contains element <code>elem</code>.
   *
   *  @param  elem    the element to check for membership.
   *  @return true, iff <code>elem</code> is contained in this set.
   */
  def contains(elem: A): Boolean = !tree.lookup(elem).isEmpty

  /** Creates a new iterator over all elements contained in this
   *  object.
   *
   *  @return the new iterator
   */
  def elements: Iterator[A] = tree.toStream.elements map (_._1)

  override def toStream: Stream[A] = tree.toStream map (_._1)

  override def foreach[U](f: A =>  U) = tree foreach { (x, y) => f(x) }

  override def rangeImpl(from: Option[A], until: Option[A]): TreeSet[A] = {
    val tree = this.tree.range(from, until)
    newSet(tree.count, tree)
  }
  override def firstKey = tree.first
  override def lastKey = tree.last
  override def compare(a0: A, a1: A) = a0.compare(a1)
}