The answer to Project Euler #11, using the Scala Actor library

euler11.scala

package euler

import scala.actors.Actor
import Actor._

object Euler011 extends Actor {

  type Matrix = Seq[Seq[Int]]
  case class CalculateMaxRequest(matrix: Matrix, from: Actor)
  case class CalculateMaxReply(matrix: Matrix, max: Int)

  var count = 0

  def execute() {
    val input = "08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08 49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00 81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65 52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91 22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80 24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50 32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70 67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21 24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72 21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95 78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92 16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57 86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58 19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40 04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66 88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69 04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36 20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16 20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54 01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48"
    val intArray = input split " " map (_.toInt) toList
    val array2D = (intArray grouped 20 toList)
    val sliced = array2D.map(row => row.sliding(4, 1).toList).sliding(4, 1).toList
    val matrices: List[Matrix] = sliced flatMap (_.transpose)
    count = matrices.size
    println("We have " + count + " matrices to process, each using an actor")
    for (matrix <- matrices) {
      val calculator = new MaxProductCalculator
      calculator.start()
      calculator ! CalculateMaxRequest(matrix, this)
    }
  }

  var max = 0
  override def act() = loop {
    react {
      case CalculateMaxReply(matrix, maxProduct) =>
        max = if (maxProduct > max) maxProduct else max
        count -= 1
        if (count == 0) {
          println("Found it.  The answer is " + max)
          exit()
        }
    }
  }

  class MaxProductCalculator extends Actor {
    override def act() = loop {
      react {
        case CalculateMaxRequest(matrix, actor) =>
          actor ! CalculateMaxReply(matrix, calculateMax(matrix))
          exit()
      }
    }

    def calculateMax(matrix: Matrix) = {

      def calculateDiagonals(matrix: Matrix) = {
        var leftTotal = 1
        var rightTotal = 1
        val end = matrix.size - 1
        for (i <- 0 to end) {
          leftTotal = leftTotal * matrix(i)(i)
          rightTotal = rightTotal * matrix(end - i)(i)
        }
        (leftTotal, rightTotal)
      }

      val horizontal = matrix.map(_ product).max
      val vertical = matrix.transpose.map(_ product).max
      val (left, right) = calculateDiagonals(matrix)
      val products = horizontal :: vertical :: left :: right :: Nil
      products max
    }

  }

}

object Runner extends Application {
  Euler011.start
  Euler011.execute
}