module patterns {

  trait Tree {}
  case class Branch(left: Tree, right: Tree) extends Tree {}
  case class Leaf(x: Int) extends Tree {}

  val tree1 = Branch(Branch(Leaf(1), Leaf(2)), Branch(Leaf(3), Leaf(4)));

  def sumLeaves(t: Tree): Int = t match {
    case Branch(l, r) => sumLeaves(l) + sumLeaves(r)
    case Leaf(x) => x
  }

  def find[a,b](it: Iterator[Pair[a, b]], x: a): Option[b] = {
    var result: Option[b] = None();
    while (it.hasNext && result.isNone) {
      val Pair(x1, y) = it.next;
      if (x == x1) result = Some(y)
    }
    result
  }

  def printFinds[a](xs: List[Pair[a, String]], x: a) =
    find(xs.elements, x) match {
      case Some(y) => System.out.println(y)
      case None() => System.out.println("no match")
    }
}