Scala Experiments

sealed class Tree[T] {
  def stream(): LazyList[T] = this match {
    case Leaf(value) => LazyList(value)
    case Branch(left, right) => left.stream() #::: right.stream()
  }
}
case class Branch[T](left: Tree[T], right: Tree[T]) extends Tree[T]
case class Leaf[T](value: T) extends Tree[T]

val tree =
  Branch(
    Leaf(1),
    Branch(
      Leaf(2),
      Leaf(3)
    )
  )

val nextInOrder = tree.stream().dropWhile(_ != 2).drop(1).headOption
println(nextInOrder)