Walk the line example from 'http://learnyouahaskell.com/a-fistful-of-monads#walk-the-line' in scala. Birds using plain scala BirdZ using scalaz

Birds.scala

package com.logikujo.scalazrepl

import scalaz._
import Scalaz._

object BirdsCommon { 
  type Pole = (Int, Int)
  trait Direction
  case object Left extends Direction
  case object Right extends Direction
}

object Birds { 
  import BirdsCommon._
  def landAny(dir:Direction)(n:Int)(pole:Pole):Option[Pole] = { 
    def land(pole:Pole):Option[Pole] = math.abs(pole._1 - pole._2) match { 
      case x if x < 4 => Some(pole)
      case _ => None
    }
    if (dir == Left) land((pole._1 + n,pole._2))
    else land(pole._1, pole._2 + n)
  }

  val landLeft = landAny(Left)_
  val landRight = landAny(Right)_

  /*
   * scala> Some(0->0).flatMap(landRight(2)).flatMap(landLeft(2)).flatMap(landRight(2))
   * res9: Option[(Int, Int)] = Some((2,4))
   *
   * scala> Some(0->0).flatMap(landLeft(1)).flatMap(landRight(4)).flatMap(landLeft(-1)).flatMap(landLeft(-2))
   * res10: Option[(Int, Int)] = None
   * 
   */
}

object BirdZ { 
  import BirdsCommon._
  def landAny(dir:Direction)(n:Int)(pole:Pole):Option[Pole] = { 
    def land(pole:Pole):Option[Pole] = (math.abs(pole._1 - pole._2) < 4) ? pole.some | none
    (dir == Left) ? land((pole._1 + n) -> pole._2) | land(pole._1 -> (pole._2 + n))
  }
  val landLeft = landAny(Left)_
  val landRight = landAny(Right)_

  /*
   * scala> (0,0).some >>= landRight(2) >>= landLeft(2) >>= landRight(2)
   * res1: Option[(Int, Int)] = Some((2,4))
   *
   * scala> (0,0).some >>= landLeft(1) >>= landRight(4) >>= landLeft(-1) >>= landRight(-2)
   * res4: Option[(Int, Int)] = None
   * 
   */
}