package test
object Go {
  trait Core {
    var next : Position = null
  }
  trait Dir
  val NEXT = new Dir{}
  val PREV = new Dir{}

  trait Position extends Core
  object head extends Core
  def current : Core = null
  def go(n : Dir) = (current,n) match {
  case (at,NEXT) if at.next == null => false
  case (at:Position,dir) => true
  }
  def main(args : Array[String]) = {
  }
}