Langton's ant

README.md

Open with scalafiddle for a live demo

Implementation of Langton's ant with scala-js-fiddle

langton.scala

val antSize=3
  var direction: Direction = North
  val delayMillis=1 // increase this to slow down
  val loopSize=1000 // increase this to accelerate
  val infinite=false

  Fiddle.draw.fillStyle = "blue"
  Fiddle.draw.font=    "20px Georgia"

  val (h, w) = (Fiddle.canvas.height, Fiddle.canvas.width)
  val (maxX, maxY) = (h / antSize, w / antSize)
  var (x, y) = (maxX/2, maxY / 2)
  var i = 0
  val blackSpots = collection.mutable.Map.empty[(Int, Int), Boolean].withDefaultValue(false)

    Fiddle.schedule(delayMillis) {
      for (i<- 1 to loopSize) {
        drawIter()
        drawAnt()
        nextIter()
      }
}
    
    def nextIter():Unit={
      i += 1
      direction =
        if (blackSpots((x, y))) direction.left
        else direction.right
      blackSpots.update((x, y), !blackSpots((x, y)))

      val (nx, ny) = checkBounds(direction.next(x, y))
      x = nx
      y = ny
}

  def checkBounds(xy:(Int,Int)) : (Int,Int) =
    if(infinite) xy
    else      {
      val (x,y)=xy
      (
      if(x>maxX) 0 else if (x<0) maxX else x,
      if(y>maxY) 0 else if (y<0) maxY else y
      )
    }
    
    def drawIter():Unit={
      Fiddle.draw.clearRect(0, 0, 100, 30)
      Fiddle.draw.fillText(i.toString, 20, 20)
    }
    
    def drawAnt() :Unit= {
      val antX=x*antSize    
      val antY=y*antSize    
  
      if (blackSpots((x, y)))
        Fiddle.draw.clearRect(antX,antY, antSize,antSize)
      else
        Fiddle.draw.fillRect(antX,antY, antSize,antSize)
    }
  }

  trait Direction {
    def left: Direction
    def right: Direction
    def next(x: Int, y: Int): (Int, Int)
  }

  object North extends Direction {
    val left = West
    val right = East
    def next(x: Int, y: Int) = (x, y - 1)
  }
  object South extends Direction {
    val left = East
    val right = West
    def next(x: Int, y: Int) = (x, y + 1)
  }
  object West extends Direction {
    val left = South
    val right = North
    def next(x: Int, y: Int) = (x - 1, y)
  }
  object East extends Direction {
    val left = North
    val right = South
    def next(x: Int, y: Int) = (x + 1, y)
  }  // $FiddleEnd