gistfile1.scala

/**
 * The Distribution type assumes works as follows:
 * For any x Water Cells (._1) there are y Fishes (._2) and z Sharks (._3)
 */
type Distribution = (Int, Int, Int)

/**
 * This object holds the Stream factory which
 * is used to fill the Ocean with a given distribution.
 * Needs the Ocean object to query an empty cell, but does
 * not add the actual instances. That means that the Cell needs
 * to be "spawned" in the ocean after every "take" operation
 * out of the Stream, otherwise there could be collisions.
 */
object SpawnStream {
  def apply(ocean:Ocean, d:Distribution):Stream[Option[Cell]] = {
    next(0, ocean, d)
  }
  
  def next(i:Int, ocean:Ocean, d:Distribution):Stream[Option[Cell]] = {
    
    val mod = i % (d._1 + d._2 + d._3);
    val cell = i match {
      case x if mod < d._1 => None
      case x if mod < d._1 + d._2 => Some(new Cell(ocean.randomFreeCell) with Fish)
      case _ => Some(new Cell(ocean.randomFreeCell) with Shark)
    } 
    
    cell #:: next(i+1, ocean, d)
  }
  
  
  def main(args:Array[String]) {
    SpawnStream(Ocean(10), (1,3,10)) take(10) foreach println _
  }
}