Scala example source code file (handover.scala)

This example Scala source code file (handover.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

activetransmitter, activetransmitter, car, car, chan, chan, control1, control2, idletransmitter, pair, string, switch, switch, transmitter

The Scala handover.scala source code

package examples.pilib

/**
 * Handover example with recursive types for channels.
 */
object handoverRecursive {

  import concurrent.pilib._

  val random = new java.util.Random()

  /**
   * Recursive type for channels that carry a channel "unit" and
   * an object of the type we define.
   */
  class Switch extends Chan[Pair[Chan[unit], Switch]]

  /**
   * Car.
   */
  def Car(talk: Chan[unit], switch: Switch): unit =
    choice (
      switch * ({ case Pair(t,s) => Car(t, s) }),
      talk(()) * ( {
        Thread.sleep(1 + random.nextInt(1000));
        System.out.println("Car emitted a message.");
        Car(talk, switch)
      })
    );

  /**
   * Control center.
   */
  def Control(talk1: Chan[unit], switch1: Switch,
              gain1: Switch, lose1: Switch, 
              talk2: Chan[unit], switch2: Switch,
              gain2: Switch, lose2: Switch): unit
  = {
    def Control1: unit= {
      Thread.sleep(1 + random.nextInt(1000));
      lose1.write(Pair(talk2, switch2));
      gain2.write(Pair(talk2, switch2));
      Control2
    }
    def Control2: unit = {
      Thread.sleep(1 + random.nextInt(1000));
      lose2.write(Pair(talk1, switch1));
      gain1.write(Pair(talk1, switch1));
      Control1
    }
    Control1
  }

  /**
  * Active transmitter.
  */
  def ActiveTransmitter(id: String, talk: Chan[unit], switch: Switch,
            gain: Switch, lose: Switch): unit
  =
    choice (
      talk * (x => {
        System.out.println(id + " received a message.")
        ActiveTransmitter(id, talk, switch, gain, lose)
      }),
      lose * ({ case Pair(t, s) => {
        switch.write(Pair(t, s))
        IdleTransmitter(id, gain, lose)
      }})
    );

  /**
   * Idle transmitter.
   */
  def IdleTransmitter(id: String, gain: Switch, lose: Switch): unit = {
    val Pair(t, s) = gain.read;
    ActiveTransmitter(id, t, s, gain, lose)
  }

  def main(args: Array[String]): unit = {
    val talk1 = new Chan[unit]
    val switch1 = new Switch
    val gain1 = new Switch
    val lose1 = new Switch
    val talk2 = new Chan[unit]
    val switch2 = new Switch
    val gain2 = new Switch
    val lose2 = new Switch
    spawn <
    Car(talk1, switch1) |
    ActiveTransmitter("Transmitter 1", talk1, switch1, gain1, lose1) |
    IdleTransmitter("Transmitter 2", gain2, lose2) |
    Control(talk1, switch1, gain1, lose1, talk2, switch2, gain2, lose2) >
  }
}

/**
* Handover example with type casts.
*/
object handoverCast {

  import concurrent.pilib._;

  val random = new java.util.Random();

  /**
  * Car.
  */
  def Car(talk: Chan[Any], switch: Chan[Any]): unit =
    choice (
      switch * (o => {
        val Pair(t,s) = o.asInstanceOf[Pair[Chan[Any],Chan[Any]]]; 
        Car(t, s)
      }),
      talk(()) * ( {
        Thread.sleep(1 + random.nextInt(1000));
        System.out.println("Car emitted a message.");
        Car(talk, switch)
      })
    );

  /**
  * Control center.
  */
  def Control(talk1: Chan[Any], switch1: Chan[Any],
              gain1: Chan[Any], lose1: Chan[Any], 
              talk2: Chan[Any], switch2: Chan[Any],
              gain2: Chan[Any], lose2: Chan[Any]): unit
  = {
    def Control1: unit = {
      Thread.sleep(1 + random.nextInt(1000));
      lose1.write(Pair(talk2, switch2));
      gain2.write(Pair(talk2, switch2));
      Control2
    }
    def Control2: unit = {
      Thread.sleep(1 + random.nextInt(1000));
      lose2.write(Pair(talk1, switch1));
      gain1.write(Pair(talk1, switch1));
      Control1
    }
    Control1
  }

  /**
   * Active transmitter.
   */
  def ActiveTransmitter(id: String, talk: Chan[Any], switch: Chan[Any],
                        gain: Chan[Any], lose: Chan[Any]): unit
  =
    choice (
      talk * (x => {
        System.out.println(id + " received a message.")
        ActiveTransmitter(id, talk, switch, gain, lose)
      }),
      lose * (o => {
        val Pair(t, s) = o.asInstanceOf[Pair[Chan[Any],Chan[Any]]]
        switch.write(Pair(t, s))
        IdleTransmitter(id, gain, lose)
      })
    )

  /**
  * Idle transmitter.
  */
  def IdleTransmitter(id: String, gain: Chan[Any], lose: Chan[Any]): unit = {
    val Pair(t, s) = gain.read.asInstanceOf[Pair[Chan[Any],Chan[Any]]]
    ActiveTransmitter(id, t, s, gain, lose)
  }

  def main(args: Array[String]): unit = {
    val talk1 = new Chan[Any]
    val switch1 = new Chan[Any]
    val gain1 = new Chan[Any]
    val lose1 = new Chan[Any]
    val talk2 = new Chan[Any]
    val switch2 = new Chan[Any]
    val gain2 = new Chan[Any]
    val lose2 = new Chan[Any]
    spawn <
    Car(talk1, switch1) |
    ActiveTransmitter("Transmitter 1", talk1, switch1, gain1, lose1) |
    IdleTransmitter("Transmitter 2", gain2, lose2) |
    Control(talk1, switch1, gain1, lose1, talk2, switch2, gain2, lose2) >
  }

}