A better scala barbershop simulator.

barbershop.scala

import scala.actors.Actor
import scala.actors.Actor._
import scala.util.Random
import scala.collection.{immutable, mutable}

val rand = new Random()

case class Customer(id: Int) {
  var shorn:Boolean = false
}

case class RequestCustomer()

val shop = actor {
  val seats = 3
  val queue = new mutable.SynchronizedQueue[Customer]()

  println("(s) the shop is open")
  
  loop { react {
    case customer: Customer =>
      println("(c) %d entering shop" format customer.id)
      if (seats < queue.size) 
        println("(s) turning away customer %d" format customer.id)
      else
        queue enqueue customer

    case request: RequestCustomer =>
      if (queue.isEmpty) 
        continue
      else
        reply(queue.dequeue)
  }}
}

val barber = actor { loop { 
  Thread.sleep(100 + rand.nextInt(400))

  shop !? RequestCustomer() match {
    case customer: Customer =>
      println("(b) cutting hair of customer %d" format customer.id)
      customer.shorn = true
  }
}}

// customers arrive at random intervals
val customers = (1 to 20) map { i =>
  val customer = new Customer(i)
  shop ! customer
  Thread.sleep(rand.nextInt(450))
  customer
}

// wait for any remaining concurrent actions to complete
Thread.sleep(2000)

val shornCount = customers.filter(_.shorn).size
println("[!] " + shornCount + " customers got haircuts today")