Merge remote-tracking branch 'erikrozendaal/SI-5331' into develop

4 files changed, 627 insertions, 57 deletions

diff --git a/src/library/scala/collection/immutable/RedBlack.scala b/src/library/scala/collection/immutable/RedBlack.scala
index 9906c9896e..83eeaa45ee 100644
--- a/src/library/scala/collection/immutable/RedBlack.scala
+++ b/src/library/scala/collection/immutable/RedBlack.scala
@@ -11,10 +11,13 @@
 package scala.collection
 package immutable
 
-/** A base class containing the implementations for `TreeMaps` and `TreeSets`.
+/** Old base class that was used by previous implementations of `TreeMaps` and `TreeSets`.
+ *
+ *  Deprecated due to various performance bugs (see [[https://issues.scala-lang.org/browse/SI-5331 SI-5331]] for more information).
  *
  *  @since 2.3
  */
+@deprecated("use `TreeMap` or `TreeSet` instead", "2.10")
 @SerialVersionUID(8691885935445612921L)
 abstract class RedBlack[A] extends Serializable {
 
@@ -287,5 +290,3 @@ abstract class RedBlack[A] extends Serializable {
     def isBlack = true
   }
 }
-
-
diff --git a/src/library/scala/collection/immutable/RedBlackTree.scala b/src/library/scala/collection/immutable/RedBlackTree.scala
new file mode 100644
index 0000000000..0f28c4997b
--- /dev/null
+++ b/src/library/scala/collection/immutable/RedBlackTree.scala
@@ -0,0 +1,485 @@
+/*                     __                                               *\
+**     ________ ___   / /  ___     Scala API                            **
+**    / __/ __// _ | / /  / _ |    (c) 2005-2011, LAMP/EPFL             **
+**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
+** /____/\___/_/ |_/____/_/ | |                                         **
+**                          |/                                          **
+\*                                                                      */
+
+
+
+package scala.collection
+package immutable
+
+import annotation.tailrec
+import annotation.meta.getter
+
+/** An object containing the RedBlack tree implementation used by for `TreeMaps` and `TreeSets`.
+ *
+ *  Implementation note: since efficiency is important for data structures this implementation
+ *  uses <code>null</code> to represent empty trees. This also means pattern matching cannot
+ *  easily be used. The API represented by the RedBlackTree object tries to hide these
+ *  optimizations behind a reasonably clean API.
+ *
+ *  @since 2.10
+ */
+private[immutable]
+object RedBlackTree {
+
+  def isEmpty(tree: Tree[_, _]): Boolean = tree eq null
+
+  def contains[A](tree: Tree[A, _], x: A)(implicit ordering: Ordering[A]): Boolean = lookup(tree, x) ne null
+  def get[A, B](tree: Tree[A, B], x: A)(implicit ordering: Ordering[A]): Option[B] = lookup(tree, x) match {
+    case null => None
+    case tree => Some(tree.value)
+  }
+
+  @tailrec
+  def lookup[A, B](tree: Tree[A, B], x: A)(implicit ordering: Ordering[A]): Tree[A, B] = if (tree eq null) null else {
+    val cmp = ordering.compare(x, tree.key)
+    if (cmp < 0) lookup(tree.left, x)
+    else if (cmp > 0) lookup(tree.right, x)
+    else tree
+  }
+
+  def count(tree: Tree[_, _]) = if (tree eq null) 0 else tree.count
+  def update[A, B, B1 >: B](tree: Tree[A, B], k: A, v: B1)(implicit ordering: Ordering[A]): Tree[A, B1] = blacken(upd(tree, k, v))
+  def delete[A, B](tree: Tree[A, B], k: A)(implicit ordering: Ordering[A]): Tree[A, B] = blacken(del(tree, k))
+  def rangeImpl[A: Ordering, B](tree: Tree[A, B], from: Option[A], until: Option[A]): Tree[A, B] = (from, until) match {
+    case (Some(from), Some(until)) => this.range(tree, from, until)
+    case (Some(from), None)        => this.from(tree, from)
+    case (None,       Some(until)) => this.until(tree, until)
+    case (None,       None)        => tree
+  }
+  def range[A: Ordering, B](tree: Tree[A, B], from: A, until: A): Tree[A, B] = blacken(doRange(tree, from, until))
+  def from[A: Ordering, B](tree: Tree[A, B], from: A): Tree[A, B] = blacken(doFrom(tree, from))
+  def to[A: Ordering, B](tree: Tree[A, B], to: A): Tree[A, B] = blacken(doTo(tree, to))
+  def until[A: Ordering, B](tree: Tree[A, B], key: A): Tree[A, B] = blacken(doUntil(tree, key))
+
+  def drop[A: Ordering, B](tree: Tree[A, B], n: Int): Tree[A, B] = blacken(doDrop(tree, n))
+  def take[A: Ordering, B](tree: Tree[A, B], n: Int): Tree[A, B] = blacken(doTake(tree, n))
+  def slice[A: Ordering, B](tree: Tree[A, B], from: Int, until: Int): Tree[A, B] = blacken(doSlice(tree, from, until))
+
+  def smallest[A, B](tree: Tree[A, B]): Tree[A, B] = {
+    if (tree eq null) throw new NoSuchElementException("empty map")
+    var result = tree
+    while (result.left ne null) result = result.left
+    result
+  }
+  def greatest[A, B](tree: Tree[A, B]): Tree[A, B] = {
+    if (tree eq null) throw new NoSuchElementException("empty map")
+    var result = tree
+    while (result.right ne null) result = result.right
+    result
+  }
+
+  def foreach[A, B, U](tree: Tree[A, B], f: ((A, B)) => U): Unit = if (tree ne null) {
+    if (tree.left ne null) foreach(tree.left, f)
+    f((tree.key, tree.value))
+    if (tree.right ne null) foreach(tree.right, f)
+  }
+  def foreachKey[A, U](tree: Tree[A, _], f: A => U): Unit = if (tree ne null) {
+    if (tree.left ne null) foreachKey(tree.left, f)
+    f(tree.key)
+    if (tree.right ne null) foreachKey(tree.right, f)
+  }
+
+  def iterator[A, B](tree: Tree[A, B]): Iterator[(A, B)] = new EntriesIterator(tree)
+  def keysIterator[A, _](tree: Tree[A, _]): Iterator[A] = new KeysIterator(tree)
+  def valuesIterator[_, B](tree: Tree[_, B]): Iterator[B] = new ValuesIterator(tree)
+
+  @tailrec
+  def nth[A, B](tree: Tree[A, B], n: Int): Tree[A, B] = {
+    val count = this.count(tree.left)
+    if (n < count) nth(tree.left, n)
+    else if (n > count) nth(tree.right, n - count - 1)
+    else tree
+  }
+
+  def isBlack(tree: Tree[_, _]) = (tree eq null) || isBlackTree(tree)
+
+  private[this] def isRedTree(tree: Tree[_, _]) = tree.isInstanceOf[RedTree[_, _]]
+  private[this] def isBlackTree(tree: Tree[_, _]) = tree.isInstanceOf[BlackTree[_, _]]
+
+  private[this] def blacken[A, B](t: Tree[A, B]): Tree[A, B] = if (t eq null) null else t.black
+
+  private[this] def mkTree[A, B](isBlack: Boolean, k: A, v: B, l: Tree[A, B], r: Tree[A, B]) =
+    if (isBlack) BlackTree(k, v, l, r) else RedTree(k, v, l, r)
+
+  private[this] def balanceLeft[A, B, B1 >: B](isBlack: Boolean, z: A, zv: B, l: Tree[A, B1], d: Tree[A, B1]): Tree[A, B1] = {
+    if (isRedTree(l) && isRedTree(l.left))
+      RedTree(l.key, l.value, BlackTree(l.left.key, l.left.value, l.left.left, l.left.right), BlackTree(z, zv, l.right, d))
+    else if (isRedTree(l) && isRedTree(l.right))
+      RedTree(l.right.key, l.right.value, BlackTree(l.key, l.value, l.left, l.right.left), BlackTree(z, zv, l.right.right, d))
+    else
+      mkTree(isBlack, z, zv, l, d)
+  }
+  private[this] def balanceRight[A, B, B1 >: B](isBlack: Boolean, x: A, xv: B, a: Tree[A, B1], r: Tree[A, B1]): Tree[A, B1] = {
+    if (isRedTree(r) && isRedTree(r.left))
+      RedTree(r.left.key, r.left.value, BlackTree(x, xv, a, r.left.left), BlackTree(r.key, r.value, r.left.right, r.right))
+    else if (isRedTree(r) && isRedTree(r.right))
+      RedTree(r.key, r.value, BlackTree(x, xv, a, r.left), BlackTree(r.right.key, r.right.value, r.right.left, r.right.right))
+    else
+      mkTree(isBlack, x, xv, a, r)
+  }
+  private[this] def upd[A, B, B1 >: B](tree: Tree[A, B], k: A, v: B1)(implicit ordering: Ordering[A]): Tree[A, B1] = if (tree eq null) {
+    RedTree(k, v, null, null)
+  } else {
+    val cmp = ordering.compare(k, tree.key)
+    if (cmp < 0) balanceLeft(isBlackTree(tree), tree.key, tree.value, upd(tree.left, k, v), tree.right)
+    else if (cmp > 0) balanceRight(isBlackTree(tree), tree.key, tree.value, tree.left, upd(tree.right, k, v))
+    else mkTree(isBlackTree(tree), k, v, tree.left, tree.right)
+  }
+
+  // Based on Stefan Kahrs' Haskell version of Okasaki's Red&Black Trees
+  // http://www.cse.unsw.edu.au/~dons/data/RedBlackTree.html
+  private[this] def del[A, B](tree: Tree[A, B], k: A)(implicit ordering: Ordering[A]): Tree[A, B] = if (tree eq null) null else {
+    def balance(x: A, xv: B, tl: Tree[A, B], tr: Tree[A, B]) = if (isRedTree(tl)) {
+      if (isRedTree(tr)) {
+        RedTree(x, xv, tl.black, tr.black)
+      } else if (isRedTree(tl.left)) {
+        RedTree(tl.key, tl.value, tl.left.black, BlackTree(x, xv, tl.right, tr))
+      } else if (isRedTree(tl.right)) {
+        RedTree(tl.right.key, tl.right.value, BlackTree(tl.key, tl.value, tl.left, tl.right.left), BlackTree(x, xv, tl.right.right, tr))
+      } else {
+        BlackTree(x, xv, tl, tr)
+      }
+    } else if (isRedTree(tr)) {
+      if (isRedTree(tr.right)) {
+        RedTree(tr.key, tr.value, BlackTree(x, xv, tl, tr.left), tr.right.black)
+      } else if (isRedTree(tr.left)) {
+        RedTree(tr.left.key, tr.left.value, BlackTree(x, xv, tl, tr.left.left), BlackTree(tr.key, tr.value, tr.left.right, tr.right))
+      } else {
+        BlackTree(x, xv, tl, tr)
+      }
+    } else {
+      BlackTree(x, xv, tl, tr)
+    }
+    def subl(t: Tree[A, B]) =
+      if (t.isInstanceOf[BlackTree[_, _]]) t.red
+      else sys.error("Defect: invariance violation; expected black, got "+t)
+
+    def balLeft(x: A, xv: B, tl: Tree[A, B], tr: Tree[A, B]) = if (isRedTree(tl)) {
+      RedTree(x, xv, tl.black, tr)
+    } else if (isBlackTree(tr)) {
+      balance(x, xv, tl, tr.red)
+    } else if (isRedTree(tr) && isBlackTree(tr.left)) {
+      RedTree(tr.left.key, tr.left.value, BlackTree(x, xv, tl, tr.left.left), balance(tr.key, tr.value, tr.left.right, subl(tr.right)))
+    } else {
+      sys.error("Defect: invariance violation")
+    }
+    def balRight(x: A, xv: B, tl: Tree[A, B], tr: Tree[A, B]) = if (isRedTree(tr)) {
+      RedTree(x, xv, tl, tr.black)
+    } else if (isBlackTree(tl)) {
+      balance(x, xv, tl.red, tr)
+    } else if (isRedTree(tl) && isBlackTree(tl.right)) {
+      RedTree(tl.right.key, tl.right.value, balance(tl.key, tl.value, subl(tl.left), tl.right.left), BlackTree(x, xv, tl.right.right, tr))
+    } else {
+      sys.error("Defect: invariance violation")
+    }
+    def delLeft = if (isBlackTree(tree.left)) balLeft(tree.key, tree.value, del(tree.left, k), tree.right) else RedTree(tree.key, tree.value, del(tree.left, k), tree.right)
+    def delRight = if (isBlackTree(tree.right)) balRight(tree.key, tree.value, tree.left, del(tree.right, k)) else RedTree(tree.key, tree.value, tree.left, del(tree.right, k))
+    def append(tl: Tree[A, B], tr: Tree[A, B]): Tree[A, B] = if (tl eq null) {
+      tr
+    } else if (tr eq null) {
+      tl
+    } else if (isRedTree(tl) && isRedTree(tr)) {
+      val bc = append(tl.right, tr.left)
+      if (isRedTree(bc)) {
+        RedTree(bc.key, bc.value, RedTree(tl.key, tl.value, tl.left, bc.left), RedTree(tr.key, tr.value, bc.right, tr.right))
+      } else {
+        RedTree(tl.key, tl.value, tl.left, RedTree(tr.key, tr.value, bc, tr.right))
+      }
+    } else if (isBlackTree(tl) && isBlackTree(tr)) {
+      val bc = append(tl.right, tr.left)
+      if (isRedTree(bc)) {
+        RedTree(bc.key, bc.value, BlackTree(tl.key, tl.value, tl.left, bc.left), BlackTree(tr.key, tr.value, bc.right, tr.right))
+      } else {
+        balLeft(tl.key, tl.value, tl.left, BlackTree(tr.key, tr.value, bc, tr.right))
+      }
+    } else if (isRedTree(tr)) {
+      RedTree(tr.key, tr.value, append(tl, tr.left), tr.right)
+    } else if (isRedTree(tl)) {
+      RedTree(tl.key, tl.value, tl.left, append(tl.right, tr))
+    } else {
+      sys.error("unmatched tree on append: " + tl + ", " + tr)
+    }
+
+    val cmp = ordering.compare(k, tree.key)
+    if (cmp < 0) delLeft
+    else if (cmp > 0) delRight
+    else append(tree.left, tree.right)
+  }
+
+  private[this] def doFrom[A, B](tree: Tree[A, B], from: A)(implicit ordering: Ordering[A]): Tree[A, B] = {
+    if (tree eq null) return null
+    if (ordering.lt(tree.key, from)) return doFrom(tree.right, from)
+    val newLeft = doFrom(tree.left, from)
+    if (newLeft eq tree.left) tree
+    else if (newLeft eq null) upd(tree.right, tree.key, tree.value)
+    else rebalance(tree, newLeft, tree.right)
+  }
+  private[this] def doTo[A, B](tree: Tree[A, B], to: A)(implicit ordering: Ordering[A]): Tree[A, B] = {
+    if (tree eq null) return null
+    if (ordering.lt(to, tree.key)) return doTo(tree.left, to)
+    val newRight = doTo(tree.right, to)
+    if (newRight eq tree.right) tree
+    else if (newRight eq null) upd(tree.left, tree.key, tree.value)
+    else rebalance(tree, tree.left, newRight)
+  }
+  private[this] def doUntil[A, B](tree: Tree[A, B], until: A)(implicit ordering: Ordering[A]): Tree[A, B] = {
+    if (tree eq null) return null
+    if (ordering.lteq(until, tree.key)) return doUntil(tree.left, until)
+    val newRight = doUntil(tree.right, until)
+    if (newRight eq tree.right) tree
+    else if (newRight eq null) upd(tree.left, tree.key, tree.value)
+    else rebalance(tree, tree.left, newRight)
+  }
+  private[this] def doRange[A, B](tree: Tree[A, B], from: A, until: A)(implicit ordering: Ordering[A]): Tree[A, B] = {
+    if (tree eq null) return null
+    if (ordering.lt(tree.key, from)) return doRange(tree.right, from, until);
+    if (ordering.lteq(until, tree.key)) return doRange(tree.left, from, until);
+    val newLeft = doFrom(tree.left, from)
+    val newRight = doUntil(tree.right, until)
+    if ((newLeft eq tree.left) && (newRight eq tree.right)) tree
+    else if (newLeft eq null) upd(newRight, tree.key, tree.value);
+    else if (newRight eq null) upd(newLeft, tree.key, tree.value);
+    else rebalance(tree, newLeft, newRight)
+  }
+
+  private[this] def doDrop[A: Ordering, B](tree: Tree[A, B], n: Int): Tree[A, B] = {
+    if (n <= 0) return tree
+    if (n >= this.count(tree)) return null
+    val count = this.count(tree.left)
+    if (n > count) return doDrop(tree.right, n - count - 1)
+    val newLeft = doDrop(tree.left, n)
+    if (newLeft eq tree.left) tree
+    else if (newLeft eq null) upd(tree.right, tree.key, tree.value)
+    else rebalance(tree, newLeft, tree.right)
+  }
+  private[this] def doTake[A: Ordering, B](tree: Tree[A, B], n: Int): Tree[A, B] = {
+    if (n <= 0) return null
+    if (n >= this.count(tree)) return tree
+    val count = this.count(tree.left)
+    if (n <= count) return doTake(tree.left, n)
+    val newRight = doTake(tree.right, n - count - 1)
+    if (newRight eq tree.right) tree
+    else if (newRight eq null) upd(tree.left, tree.key, tree.value)
+    else rebalance(tree, tree.left, newRight)
+  }
+  private[this] def doSlice[A: Ordering, B](tree: Tree[A, B], from: Int, until: Int): Tree[A, B] = {
+    if (tree eq null) return null
+    val count = this.count(tree.left)
+    if (from > count) return doSlice(tree.right, from - count - 1, until - count - 1)
+    if (until <= count) return doSlice(tree.left, from, until)
+    val newLeft = doDrop(tree.left, from)
+    val newRight = doTake(tree.right, until - count - 1)
+    if ((newLeft eq tree.left) && (newRight eq tree.right)) tree
+    else if (newLeft eq null) upd(newRight, tree.key, tree.value)
+    else if (newRight eq null) upd(newLeft, tree.key, tree.value)
+    else rebalance(tree, newLeft, newRight)
+  }
+
+  // The zipper returned might have been traversed left-most (always the left child)
+  // or right-most (always the right child). Left trees are traversed right-most,
+  // and right trees are traversed leftmost.
+
+  // Returns the zipper for the side with deepest black nodes depth, a flag
+  // indicating whether the trees were unbalanced at all, and a flag indicating
+  // whether the zipper was traversed left-most or right-most.
+
+  // If the trees were balanced, returns an empty zipper
+  private[this] def compareDepth[A, B](left: Tree[A, B], right: Tree[A, B]): (List[Tree[A, B]], Boolean, Boolean, Int) = {
+    // Once a side is found to be deeper, unzip it to the bottom
+    def unzip(zipper: List[Tree[A, B]], leftMost: Boolean): List[Tree[A, B]] = {
+      val next = if (leftMost) zipper.head.left else zipper.head.right
+      next match {
+        case null => zipper
+        case node => unzip(node :: zipper, leftMost)
+      }
+    }
+
+    // Unzip left tree on the rightmost side and right tree on the leftmost side until one is
+    // found to be deeper, or the bottom is reached
+    def unzipBoth(left: Tree[A, B],
+                  right: Tree[A, B],
+                  leftZipper: List[Tree[A, B]],
+                  rightZipper: List[Tree[A, B]],
+                  smallerDepth: Int): (List[Tree[A, B]], Boolean, Boolean, Int) = {
+      if (isBlackTree(left) && isBlackTree(right)) {
+        unzipBoth(left.right, right.left, left :: leftZipper, right :: rightZipper, smallerDepth + 1)
+      } else if (isRedTree(left) && isRedTree(right)) {
+        unzipBoth(left.right, right.left, left :: leftZipper, right :: rightZipper, smallerDepth)
+      } else if (isRedTree(right)) {
+        unzipBoth(left, right.left, leftZipper, right :: rightZipper, smallerDepth)
+      } else if (isRedTree(left)) {
+        unzipBoth(left.right, right, left :: leftZipper, rightZipper, smallerDepth)
+      } else if ((left eq null) && (right eq null)) {
+        (Nil, true, false, smallerDepth)
+      } else if ((left eq null) && isBlackTree(right)) {
+        val leftMost = true
+        (unzip(right :: rightZipper, leftMost), false, leftMost, smallerDepth)
+      } else if (isBlackTree(left) && (right eq null)) {
+        val leftMost = false
+        (unzip(left :: leftZipper, leftMost), false, leftMost, smallerDepth)
+      } else {
+        sys.error("unmatched trees in unzip: " + left + ", " + right)
+      }
+    }
+    unzipBoth(left, right, Nil, Nil, 0)
+  }
+
+  private[this] def rebalance[A, B](tree: Tree[A, B], newLeft: Tree[A, B], newRight: Tree[A, B]) = {
+    // This is like drop(n-1), but only counting black nodes
+    def  findDepth(zipper: List[Tree[A, B]], depth: Int): List[Tree[A, B]] = zipper match {
+      case head :: tail if isBlackTree(head) =>
+        if (depth == 1) zipper else findDepth(tail, depth - 1)
+      case _ :: tail => findDepth(tail, depth)
+      case Nil => sys.error("Defect: unexpected empty zipper while computing range")
+    }
+
+    // Blackening the smaller tree avoids balancing problems on union;
+    // this can't be done later, though, or it would change the result of compareDepth
+    val blkNewLeft = blacken(newLeft)
+    val blkNewRight = blacken(newRight)
+    val (zipper, levelled, leftMost, smallerDepth) = compareDepth(blkNewLeft, blkNewRight)
+
+    if (levelled) {
+      BlackTree(tree.key, tree.value, blkNewLeft, blkNewRight)
+    } else {
+      val zipFrom = findDepth(zipper, smallerDepth)
+      val union = if (leftMost) {
+        RedTree(tree.key, tree.value, blkNewLeft, zipFrom.head)
+      } else {
+        RedTree(tree.key, tree.value, zipFrom.head, blkNewRight)
+      }
+      val zippedTree = zipFrom.tail.foldLeft(union: Tree[A, B]) { (tree, node) =>
+        if (leftMost)
+          balanceLeft(isBlackTree(node), node.key, node.value, tree, node.right)
+        else
+          balanceRight(isBlackTree(node), node.key, node.value, node.left, tree)
+      }
+      zippedTree
+    }
+  }
+
+  /*
+   * Forcing direct fields access using the @inline annotation helps speed up
+   * various operations (especially smallest/greatest and update/delete).
+   *
+   * Unfortunately the direct field access is not guaranteed to work (but
+   * works on the current implementation of the Scala compiler).
+   *
+   * An alternative is to implement the these classes using plain old Java code...
+   */
+  sealed abstract class Tree[A, +B](
+    @(inline @getter) final val key: A,
+    @(inline @getter) final val value: B,
+    @(inline @getter) final val left: Tree[A, B],
+    @(inline @getter) final val right: Tree[A, B])
+  extends Serializable {
+    final val count: Int = 1 + RedBlackTree.count(left) + RedBlackTree.count(right)
+    def black: Tree[A, B]
+    def red: Tree[A, B]
+  }
+  final class RedTree[A, +B](key: A,
+                             value: B,
+                             left: Tree[A, B],
+                             right: Tree[A, B]) extends Tree[A, B](key, value, left, right) {
+    override def black: Tree[A, B] = BlackTree(key, value, left, right)
+    override def red: Tree[A, B] = this
+    override def toString: String = "RedTree(" + key + ", " + value + ", " + left + ", " + right + ")"
+  }
+  final class BlackTree[A, +B](key: A,
+                               value: B,
+                               left: Tree[A, B],
+                               right: Tree[A, B]) extends Tree[A, B](key, value, left, right) {
+    override def black: Tree[A, B] = this
+    override def red: Tree[A, B] = RedTree(key, value, left, right)
+    override def toString: String = "BlackTree(" + key + ", " + value + ", " + left + ", " + right + ")"
+  }
+
+  object RedTree {
+    @inline def apply[A, B](key: A, value: B, left: Tree[A, B], right: Tree[A, B]) = new RedTree(key, value, left, right)
+    def unapply[A, B](t: RedTree[A, B]) = Some((t.key, t.value, t.left, t.right))
+  }
+  object BlackTree {
+    @inline def apply[A, B](key: A, value: B, left: Tree[A, B], right: Tree[A, B]) = new BlackTree(key, value, left, right)
+    def unapply[A, B](t: BlackTree[A, B]) = Some((t.key, t.value, t.left, t.right))
+  }
+
+  private[this] abstract class TreeIterator[A, B, R](tree: Tree[A, B]) extends Iterator[R] {
+    protected[this] def nextResult(tree: Tree[A, B]): R
+
+    override def hasNext: Boolean = next ne null
+
+    override def next: R = next match {
+      case null =>
+        throw new NoSuchElementException("next on empty iterator")
+      case tree =>
+        next = findNext(tree.right)
+        nextResult(tree)
+    }
+
+    @tailrec
+    private[this] def findNext(tree: Tree[A, B]): Tree[A, B] = {
+      if (tree eq null) popPath()
+      else if (tree.left eq null) tree
+      else {
+        pushPath(tree)
+        findNext(tree.left)
+      }
+    }
+
+    private[this] def pushPath(tree: Tree[A, B]) {
+      try {
+        path(index) = tree
+        index += 1
+      } catch {
+        case _: ArrayIndexOutOfBoundsException =>
+          /*
+           * Either the tree became unbalanced or we calculated the maximum height incorrectly.
+           * To avoid crashing the iterator we expand the path array. Obviously this should never
+           * happen...
+           *
+           * An exception handler is used instead of an if-condition to optimize the normal path.
+           * This makes a large difference in iteration speed!
+           */
+          assert(index >= path.length)
+          path :+= null
+          pushPath(tree)
+      }
+    }
+    private[this] def popPath(): Tree[A, B] = if (index == 0) null else {
+      index -= 1
+      path(index)
+    }
+
+    private[this] var path = if (tree eq null) null else {
+      /*
+       * According to "Ralf Hinze. Constructing red-black trees" [http://www.cs.ox.ac.uk/ralf.hinze/publications/#P5]
+       * the maximum height of a red-black tree is 2*log_2(n + 2) - 2.
+       *
+       * According to {@see Integer#numberOfLeadingZeros} ceil(log_2(n)) = (32 - Integer.numberOfLeadingZeros(n - 1))
+       *
+       * We also don't store the deepest nodes in the path so the maximum path length is further reduced by one.
+       */
+      val maximumHeight = 2 * (32 - Integer.numberOfLeadingZeros(tree.count + 2 - 1)) - 2 - 1
+      new Array[Tree[A, B]](maximumHeight)
+    }
+    private[this] var index = 0
+    private[this] var next: Tree[A, B] = findNext(tree)
+  }
+
+  private[this] class EntriesIterator[A, B](tree: Tree[A, B]) extends TreeIterator[A, B, (A, B)](tree) {
+    override def nextResult(tree: Tree[A, B]) = (tree.key, tree.value)
+  }
+
+  private[this] class KeysIterator[A, B](tree: Tree[A, B]) extends TreeIterator[A, B, A](tree) {
+    override def nextResult(tree: Tree[A, B]) = tree.key
+  }
+
+  private[this] class ValuesIterator[A, B](tree: Tree[A, B]) extends TreeIterator[A, B, B](tree) {
+    override def nextResult(tree: Tree[A, B]) = tree.value
+  }
+}
diff --git a/src/library/scala/collection/immutable/TreeMap.scala b/src/library/scala/collection/immutable/TreeMap.scala
index ef0eac3701..dc4f79be35 100644
--- a/src/library/scala/collection/immutable/TreeMap.scala
+++ b/src/library/scala/collection/immutable/TreeMap.scala
@@ -12,6 +12,7 @@ package scala.collection
 package immutable
 
 import generic._
+import immutable.{RedBlackTree => RB}
 import mutable.Builder
 import annotation.bridge
 
@@ -23,7 +24,6 @@ object TreeMap extends ImmutableSortedMapFactory[TreeMap] {
   def empty[A, B](implicit ord: Ordering[A]) = new TreeMap[A, B]()(ord)
   /** $sortedMapCanBuildFromInfo */
   implicit def canBuildFrom[A, B](implicit ord: Ordering[A]): CanBuildFrom[Coll, (A, B), TreeMap[A, B]] = new SortedMapCanBuildFrom[A, B]
-  private def make[A, B](s: Int, t: RedBlack[A]#Tree[B])(implicit ord: Ordering[A]) = new TreeMap[A, B](s, t)(ord)
 }
 
 /** This class implements immutable maps using a tree.
@@ -46,31 +46,79 @@ object TreeMap extends ImmutableSortedMapFactory[TreeMap] {
  *  @define mayNotTerminateInf
  *  @define willNotTerminateInf
  */
-class TreeMap[A, +B](override val size: Int, t: RedBlack[A]#Tree[B])(implicit val ordering: Ordering[A])
-  extends RedBlack[A]
-     with SortedMap[A, B]
+class TreeMap[A, +B] private (tree: RB.Tree[A, B])(implicit val ordering: Ordering[A])
+  extends SortedMap[A, B]
      with SortedMapLike[A, B, TreeMap[A, B]]
      with MapLike[A, B, TreeMap[A, B]]
      with Serializable {
 
+  @deprecated("use `ordering.lt` instead", "2.10")
   def isSmaller(x: A, y: A) = ordering.lt(x, y)
 
   override protected[this] def newBuilder : Builder[(A, B), TreeMap[A, B]] =
     TreeMap.newBuilder[A, B]
 
-  def this()(implicit ordering: Ordering[A]) = this(0, null)(ordering)
+  override def size = RB.count(tree)
 
-  protected val tree: RedBlack[A]#Tree[B] = if (size == 0) Empty else t
+  def this()(implicit ordering: Ordering[A]) = this(null)(ordering)
 
-  override def rangeImpl(from : Option[A], until : Option[A]): TreeMap[A,B] = {
-    val ntree = tree.range(from,until)
-    new TreeMap[A,B](ntree.count, ntree)
-  }
+  override def rangeImpl(from: Option[A], until: Option[A]): TreeMap[A, B] = new TreeMap[A, B](RB.rangeImpl(tree, from, until))
+  override def range(from: A, until: A): TreeMap[A, B] = new TreeMap[A, B](RB.range(tree, from, until))
+  override def from(from: A): TreeMap[A, B] = new TreeMap[A, B](RB.from(tree, from))
+  override def to(to: A): TreeMap[A, B] = new TreeMap[A, B](RB.to(tree, to))
+  override def until(until: A): TreeMap[A, B] = new TreeMap[A, B](RB.until(tree, until))
 
-  override def firstKey = t.first
-  override def lastKey = t.last
+  override def firstKey = RB.smallest(tree).key
+  override def lastKey = RB.greatest(tree).key
   override def compare(k0: A, k1: A): Int = ordering.compare(k0, k1)
 
+  override def head = {
+    val smallest = RB.smallest(tree)
+    (smallest.key, smallest.value)
+  }
+  override def headOption = if (RB.isEmpty(tree)) None else Some(head)
+  override def last = {
+    val greatest = RB.greatest(tree)
+    (greatest.key, greatest.value)
+  }
+  override def lastOption = if (RB.isEmpty(tree)) None else Some(last)
+
+  override def tail = new TreeMap(RB.delete(tree, firstKey))
+  override def init = new TreeMap(RB.delete(tree, lastKey))
+
+  override def drop(n: Int) = {
+    if (n <= 0) this
+    else if (n >= size) empty
+    else new TreeMap(RB.drop(tree, n))
+  }
+
+  override def take(n: Int) = {
+    if (n <= 0) empty
+    else if (n >= size) this
+    else new TreeMap(RB.take(tree, n))
+  }
+
+  override def slice(from: Int, until: Int) = {
+    if (until <= from) empty
+    else if (from <= 0) take(until)
+    else if (until >= size) drop(from)
+    else new TreeMap(RB.slice(tree, from, until))
+  }
+
+  override def dropRight(n: Int) = take(size - n)
+  override def takeRight(n: Int) = drop(size - n)
+  override def splitAt(n: Int) = (take(n), drop(n))
+
+  private[this] def countWhile(p: ((A, B)) => Boolean): Int = {
+    var result = 0
+    val it = iterator
+    while (it.hasNext && p(it.next)) result += 1
+    result
+  }
+  override def dropWhile(p: ((A, B)) => Boolean) = drop(countWhile(p))
+  override def takeWhile(p: ((A, B)) => Boolean) = take(countWhile(p))
+  override def span(p: ((A, B)) => Boolean) = splitAt(countWhile(p))
+
   /** A factory to create empty maps of the same type of keys.
    */
   override def empty: TreeMap[A, B] = TreeMap.empty[A, B](ordering)
@@ -84,10 +132,7 @@ class TreeMap[A, +B](override val size: Int, t: RedBlack[A]#Tree[B])(implicit va
    *  @param value   the value to be associated with `key`
    *  @return        a new $coll with the updated binding
    */
-  override def updated [B1 >: B](key: A, value: B1): TreeMap[A, B1] = {
-    val newsize = if (tree.lookup(key).isEmpty) size + 1 else size
-    TreeMap.make(newsize, tree.update(key, value))
-  }
+  override def updated [B1 >: B](key: A, value: B1): TreeMap[A, B1] = new TreeMap(RB.update(tree, key, value))
 
   /** Add a key/value pair to this map.
    *  @tparam   B1   type of the value of the new binding, a supertype of `B`
@@ -128,14 +173,13 @@ class TreeMap[A, +B](override val size: Int, t: RedBlack[A]#Tree[B])(implicit va
    *  @return       a new $coll with the inserted binding, if it wasn't present in the map
    */
   def insert [B1 >: B](key: A, value: B1): TreeMap[A, B1] = {
-    assert(tree.lookup(key).isEmpty)
-    TreeMap.make(size + 1, tree.update(key, value))
+    assert(!RB.contains(tree, key))
+    new TreeMap(RB.update(tree, key, value))
   }
 
   def - (key:A): TreeMap[A, B] =
-    if (tree.lookup(key).isEmpty) this
-    else if (size == 1) empty
-    else TreeMap.make(size - 1, tree.delete(key))
+    if (!RB.contains(tree, key)) this
+    else new TreeMap(RB.delete(tree, key))
 
   /** Check if this map maps `key` to a value and return the
    *  value if it exists.
@@ -143,21 +187,22 @@ class TreeMap[A, +B](override val size: Int, t: RedBlack[A]#Tree[B])(implicit va
    *  @param  key     the key of the mapping of interest
    *  @return         the value of the mapping, if it exists
    */
-  override def get(key: A): Option[B] = tree.lookup(key) match {
-    case n: NonEmpty[b] => Some(n.value)
-    case _ => None
-  }
+  override def get(key: A): Option[B] = RB.get(tree, key)
 
   /** Creates a new iterator over all elements contained in this
    *  object.
    *
    *  @return the new iterator
    */
-  def iterator: Iterator[(A, B)] = tree.toStream.iterator
+  override def iterator: Iterator[(A, B)] = RB.iterator(tree)
+
+  override def keysIterator: Iterator[A] = RB.keysIterator(tree)
+  override def valuesIterator: Iterator[B] = RB.valuesIterator(tree)
 
-  override def toStream: Stream[(A, B)] = tree.toStream
+  override def contains(key: A): Boolean = RB.contains(tree, key)
+  override def isDefinedAt(key: A): Boolean = RB.contains(tree, key)
 
-  override def foreach[U](f : ((A,B)) =>  U) = tree foreach { case (x, y) => f(x, y) }
+  override def foreach[U](f : ((A,B)) =>  U) = RB.foreach(tree, f)
 }
 
 
diff --git a/src/library/scala/collection/immutable/TreeSet.scala b/src/library/scala/collection/immutable/TreeSet.scala
index 8b90ece143..1b3d72ceb7 100644
--- a/src/library/scala/collection/immutable/TreeSet.scala
+++ b/src/library/scala/collection/immutable/TreeSet.scala
@@ -12,6 +12,7 @@ package scala.collection
 package immutable
 
 import generic._
+import immutable.{RedBlackTree => RB}
 import mutable.{ Builder, SetBuilder }
 
 /** $factoryInfo
@@ -46,20 +47,61 @@ object TreeSet extends ImmutableSortedSetFactory[TreeSet] {
  *  @define mayNotTerminateInf
  *  @define willNotTerminateInf
  */
-@SerialVersionUID(-234066569443569402L)
-class TreeSet[A](override val size: Int, t: RedBlack[A]#Tree[Unit])
-                (implicit val ordering: Ordering[A])
-  extends RedBlack[A] with SortedSet[A] with SortedSetLike[A, TreeSet[A]] with Serializable {
+@SerialVersionUID(-5685982407650748405L)
+class TreeSet[A] private (tree: RB.Tree[A, Unit])(implicit val ordering: Ordering[A])
+  extends SortedSet[A] with SortedSetLike[A, TreeSet[A]] with Serializable {
 
   override def stringPrefix = "TreeSet"
 
-  def isSmaller(x: A, y: A) = compare(x,y) < 0
+  override def size = RB.count(tree)
+
+  override def head = RB.smallest(tree).key
+  override def headOption = if (RB.isEmpty(tree)) None else Some(head)
+  override def last = RB.greatest(tree).key
+  override def lastOption = if (RB.isEmpty(tree)) None else Some(last)
+
+  override def tail = new TreeSet(RB.delete(tree, firstKey))
+  override def init = new TreeSet(RB.delete(tree, lastKey))
+
+  override def drop(n: Int) = {
+    if (n <= 0) this
+    else if (n >= size) empty
+    else newSet(RB.drop(tree, n))
+  }
 
-  def this()(implicit ordering: Ordering[A]) = this(0, null)(ordering)
+  override def take(n: Int) = {
+    if (n <= 0) empty
+    else if (n >= size) this
+    else newSet(RB.take(tree, n))
+  }
 
-  protected val tree: RedBlack[A]#Tree[Unit] = if (size == 0) Empty else t
+  override def slice(from: Int, until: Int) = {
+    if (until <= from) empty
+    else if (from <= 0) take(until)
+    else if (until >= size) drop(from)
+    else newSet(RB.slice(tree, from, until))
+  }
 
-  private def newSet(s: Int, t: RedBlack[A]#Tree[Unit]) = new TreeSet[A](s, t)
+  override def dropRight(n: Int) = take(size - n)
+  override def takeRight(n: Int) = drop(size - n)
+  override def splitAt(n: Int) = (take(n), drop(n))
+
+  private[this] def countWhile(p: A => Boolean): Int = {
+    var result = 0
+    val it = iterator
+    while (it.hasNext && p(it.next)) result += 1
+    result
+  }
+  override def dropWhile(p: A => Boolean) = drop(countWhile(p))
+  override def takeWhile(p: A => Boolean) = take(countWhile(p))
+  override def span(p: A => Boolean) = splitAt(countWhile(p))
+
+  @deprecated("use `ordering.lt` instead", "2.10")
+  def isSmaller(x: A, y: A) = compare(x,y) < 0
+
+  def this()(implicit ordering: Ordering[A]) = this(null)(ordering)
+
+  private def newSet(t: RB.Tree[A, Unit]) = new TreeSet[A](t)
 
   /** A factory to create empty sets of the same type of keys.
    */
@@ -70,10 +112,7 @@ class TreeSet[A](override val size: Int, t: RedBlack[A]#Tree[Unit])
    *  @param elem    a new element to add.
    *  @return        a new $coll containing `elem` and all the elements of this $coll.
    */
-  def + (elem: A): TreeSet[A] = {
-    val newsize = if (tree.lookup(elem).isEmpty) size + 1 else size
-    newSet(newsize, tree.update(elem, ()))
-  }
+  def + (elem: A): TreeSet[A] = newSet(RB.update(tree, elem, ()))
 
   /** A new `TreeSet` with the entry added is returned,
    *  assuming that elem is <em>not</em> in the TreeSet.
@@ -82,8 +121,8 @@ class TreeSet[A](override val size: Int, t: RedBlack[A]#Tree[Unit])
    *  @return        a new $coll containing `elem` and all the elements of this $coll.
    */
   def insert(elem: A): TreeSet[A] = {
-    assert(tree.lookup(elem).isEmpty)
-    newSet(size + 1, tree.update(elem, ()))
+    assert(!RB.contains(tree, elem))
+    newSet(RB.update(tree, elem, ()))
   }
 
   /** Creates a new `TreeSet` with the entry removed.
@@ -92,31 +131,31 @@ class TreeSet[A](override val size: Int, t: RedBlack[A]#Tree[Unit])
    *  @return        a new $coll containing all the elements of this $coll except `elem`.
    */
   def - (elem:A): TreeSet[A] =
-    if (tree.lookup(elem).isEmpty) this
-    else newSet(size - 1, tree delete elem)
+    if (!RB.contains(tree, elem)) this
+    else newSet(RB.delete(tree, elem))
 
   /** Checks if this set contains element `elem`.
    *
    *  @param  elem    the element to check for membership.
    *  @return true, iff `elem` is contained in this set.
    */
-  def contains(elem: A): Boolean = !tree.lookup(elem).isEmpty
+  def contains(elem: A): Boolean = RB.contains(tree, elem)
 
   /** Creates a new iterator over all elements contained in this
    *  object.
    *
    *  @return the new iterator
    */
-  def iterator: Iterator[A] = tree.toStream.iterator map (_._1)
+  def iterator: Iterator[A] = RB.keysIterator(tree)
 
-  override def toStream: Stream[A] = tree.toStream map (_._1)
+  override def foreach[U](f: A =>  U) = RB.foreachKey(tree, f)
 
-  override def foreach[U](f: A =>  U) = tree foreach { (x, y) => f(x) }
+  override def rangeImpl(from: Option[A], until: Option[A]): TreeSet[A] = newSet(RB.rangeImpl(tree, from, until))
+  override def range(from: A, until: A): TreeSet[A] = newSet(RB.range(tree, from, until))
+  override def from(from: A): TreeSet[A] = newSet(RB.from(tree, from))
+  override def to(to: A): TreeSet[A] = newSet(RB.to(tree, to))
+  override def until(until: A): TreeSet[A] = newSet(RB.until(tree, until))
 
-  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 firstKey = head
+  override def lastKey = last
 }