build.sbt

scalaVersion := "2.11.7"

libraryDependencies += "org.scalaz" %% "scalaz-core" % "7.1.4"

KnightPos.scala

import scalaz._, Scalaz._

case class KnightPos(c: Int, r: Int) {
  def move: List[KnightPos] =
    for {
      KnightPos(c2, r2) <- List(KnightPos(c + 2, r - 1), KnightPos(c + 2, r + 1),
      KnightPos(c - 2, r - 1), KnightPos(c - 2, r + 1),
      KnightPos(c + 1, r - 2), KnightPos(c + 1, r + 2),
      KnightPos(c - 1, r - 2), KnightPos(c - 1, r + 2)) if (
      ((1 |-> 8) element c2) && ((1 |-> 8) contains r2))
    } yield KnightPos(c2, r2)

  val moveK: Kleisli[List, KnightPos, KnightPos] = Kleisli(_.move)

  def in(n: Int): List[KnightPos] =
    moveK.endo.multiply(n).run.run(this)

  def canReachIn(n: Int, end: KnightPos): Boolean = in(n) contains end
}