binaryTree.scala

import scala.language.implicitConversions

case class Node(nodeVal:Any, left:Option[Node] = None, right:Option[Node] = None)
{
	def preorder(f:Node => Unit) {
		f( this )
		left.map( _ preorder f )
		right.map( _ preorder f )
	}
}

implicit def nodeToSomeNode( n:Node ) = Some[Node](n)

val tree = (
	Node( "HEAD",
		Node( "  LEFT_CHILD",
			Node( "    LEFT_CHILD_LEFT"),
			Node( "    LEFT_CHILD_RIGHT",
				Node( "      LCR_L"),
				Node( "      LCR_R")
			)
 		),
		Node( "  RIGHT_CHILD",
			Node( "    RIGHT_CHILD_LEFT"),
			Node( "    RIGHT_CHILD_RIGHT")
		)
	)
)

println( tree + "\n" )
tree.preorder( e => println(e.nodeVal) )