How to acheive tail call optimization while traversing tree-like structure using continuation-passing style http://stackoverflow.com/q/20164061/443366

traverseTree.scala

import util.control.TailCalls._

sealed abstract class Tree
case class Leaf(n: Int) extends Tree
case class Node(left: Tree, right: Tree) extends Tree

lazy val numbers = Seq.range(1, 20)
lazy val imbalancedTree = numbers.map(Leaf).foldLeft[Tree](Leaf(0))(Node)

def traverseTree(tree: Tree)(action: Int => Unit): Unit = {
  def traverseTreeRec(tree: Tree, continuation: () => TailRec[Unit]): TailRec[Unit] = tree match {
    case Leaf(n) => {
      action(n)
      continuation()
    }
    case Node(n1, n2) =>
      tailcall(traverseTreeRec(n1,
        () => traverseTreeRec(n2,
          () => tailcall(continuation()))))
  }
  traverseTreeRec(tree, () => done(())).result
}

traverseTree(imbalancedTree)((n: Int) => println(n))