List Zipper

ListZipper.scala

case class ListZipper[+A](lefts: List[A], x: A, rights: List[A]) {
  def map[B](f: A => B): ListZipper[B] =
    sys.error("todo")

  // map with zipper context
  def coFlatMap[B](f: ListZipper[A] => B): ListZipper[B] =
    sys.error("todo")

  def findRight(p: A => Boolean): Option[ListZipper[A]] =
    sys.error("todo")

  def findLeft(p: A => Boolean): Option[ListZipper[A]] =
    sys.error("todo")

  def :=[AA >: A](a: AA): ListZipper[AA] =
    ListZipper(lefts, a, rights)

  def toList: List[A] =
    lefts.reverse ::: x :: rights
}

object ListZipper {
  def fromList[A](a: List[A]): Option[ListZipper[A]] =
    a match {
      case Nil => None
      case h::t => Some(ListZipper(Nil, h, t))
    }
}