Conway's Game of Life

GameOfLife.scala

package gameoflife

object GameOfLife {
  def run() {
    var g = new Generation(50, 50)
    // Blinker
    g.set(1, 1, true)
    g.set(2, 1, true)
    g.set(3, 1, true)

    // Glider
    g.set(6, 3, true)
    g.set(7, 3, true)
    g.set(8, 3, true)
    g.set(8, 2, true)
    g.set(6, 1, true)

    println(g)
    println

    (0 until 10).foreach {i => g = g.evolve; println(g); println}
  }

  def main(args: Array[String]) {
    run()
  }
}

Generation.scala

package gameoflife

class Generation(width: Int, height: Int) {
  private val cells = new Array[Boolean](width * height)

  private def index(x: Int, y: Int) = x + width * y

  def set(x: Int, y: Int, state: Boolean) =
    cells(index(x, y)) = state

  def get(x: Int, y: Int) =
    cells(index(x, y))

  private def neighbours(x: Int, y: Int) =
    for (a <- (x-1) until (x+1) inclusive;
         b <- (y-1) until (y+1) inclusive;
         if !(a==x && b==y) && a>=0 && a<width && b>=0 && b<height)
      yield cells(index(a, b))

  private def livingNeighbours(x: Int, y: Int) =
    (neighbours (x, y) foldLeft 0) { (c, b) => if (b) (c+1) else c }

  override def toString = {
    val sb = new StringBuilder(cells.length)
    cells.foreach(c => sb.append(if (c) 'X' else '-'))
    sb.toString.grouped(width).mkString("\n")
  }

  def evolve() = {
    val g = new Generation(width, height)
    (0 until width).foreach { x =>
      (0 until height).foreach{ y =>
        g.set(x, y, evolveCell(x, y))
      }
    }
    g
  }

  private def evolveCell(x: Int, y: Int) = {
    val neighbours = livingNeighbours(x, y)
    val lives = get(x, y)
    (lives && (neighbours == 2 || neighbours == 3)
      || (!lives && neighbours == 3))
  }
}