scala script to calculate gridworld

gridworld.scala

// To run: scala gridworld.scala

val l = 1.0
val R = -200

class Cell(val initValue: Option[Double], var value: Option[Double] = None) {
  var x0: Int = -9999
  var y0: Int = -9999
  var world: IndexedSeq[IndexedSeq[Cell]] = null
  value = initValue

  override def toString = "Cell(" + value + ")"

  def tryMove(c: Cell) = if (c.value.isDefined) c else this
  def up = tryMove(world(y0 - 1 max 0)(x0))
  def down = tryMove(world(y0 + 1 min 2)(x0))
  def left = tryMove(world(y0)(x0 - 1 max 0))
  def right = tryMove(world(y0)(x0 + 1 min 3))

  def moveVal(c1: Cell, c2: Cell, c3: Cell): Double = {
    (0.8 * c1.value.get +
     0.1 * c2.value.get +
     0.1 * c3.value.get)
  }

  def update {
    if (initValue == Some(0.0)) {
      value = Some((moveVal(up, left, right) max
                    moveVal(down, left, right) max
                    moveVal(left, up, down) max
                    moveVal(right, up, down)) * l + R)
    }
  }

  def policy =
    if (initValue == Some(0.0)) {
      val m = Map(moveVal(up, left, right) -> "up",
                  moveVal(down, left, right) -> "down",
                  moveVal(left, up, down) -> "left",
                  moveVal(right, up, down) -> "right")
      //println(m)
      m(m.keys.max)
    } else "---"
}

val world: IndexedSeq[IndexedSeq[Cell]] =
  IndexedSeq(IndexedSeq(new Cell(Some(0)), new Cell(Some(0)), new Cell(Some(0)), new Cell(Some(100))),
             IndexedSeq(new Cell(Some(0)), new Cell(None), new Cell(Some(0)), new Cell(Some(-100))),
             IndexedSeq(new Cell(Some(0)), new Cell(Some(0)), new Cell(Some(0)), new Cell(Some(0))))

for (y <- (0 to 2)) {
  for (x <- (0 to 3)) {
    world(y)(x).x0 = x
    world(y)(x).y0 = y
    world(y)(x).world = world
  }
}

var isChanged = true
var loops = 0
while (isChanged) {
  loops += 1
  isChanged = false
  for {
    cells <- world
    cell <- cells
  } {
    val last = cell.value
    cell.update
    if (last != cell.value)
      isChanged = true
  }
}
println("Iterations: " + loops.toString)
println
println("Values:")
for (cells <- world)
  println(cells.toString)
println
println("Policies:")
for (cells <- world)
  println(cells.map { _.policy }.toString)