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authorGilles Dubochet <gilles.dubochet@epfl.ch>2005-12-16 18:44:33 +0000
committerGilles Dubochet <gilles.dubochet@epfl.ch>2005-12-16 18:44:33 +0000
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Created proper 'docs' folder for new layout.
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+package examples;
+
+import java.util.Date;
+import scala.concurrent._;
+
+/** A simple demonstrator program implementing an online auction service
+ * The example uses the actor abstraction defined in the API of
+ * package scala.concurrent.
+ */
+trait AuctionMessage;
+case class
+ Offer(bid: int, client: Actor), // make a bid
+ Inquire(client: Actor) extends AuctionMessage; // inquire status
+
+trait AuctionReply;
+case class
+ Status(asked: int, expiration: Date), // asked sum, expiration date
+ BestOffer(), // yours is the best offer
+ BeatenOffer(maxBid: int), // offer beaten by maxBid
+ AuctionConcluded(seller: Actor, client: Actor), // auction concluded
+ AuctionFailed(), // failed with no bids
+ AuctionOver() extends AuctionReply; // bidding is closed
+
+class Auction(seller: Actor, minBid: int, closing: Date) extends Actor {
+
+ val timeToShutdown = 3600000; // msec
+ val bidIncrement = 10;
+
+ override def run() = {
+ var maxBid = minBid - bidIncrement;
+ var maxBidder: Actor = null;
+ var running = true;
+
+ while (running) {
+ receiveWithin (closing.getTime() - new Date().getTime()) {
+
+ case Offer(bid, client) =>
+ if (bid >= maxBid + bidIncrement) {
+ if (maxBid >= minBid)
+ maxBidder send BeatenOffer(bid);
+ maxBid = bid;
+ maxBidder = client;
+ client send BestOffer()
+ } else {
+ client send BeatenOffer(maxBid)
+ }
+
+ case Inquire(client) =>
+ client send Status(maxBid, closing)
+
+ case TIMEOUT() =>
+ if (maxBid >= minBid) {
+ val reply = AuctionConcluded(seller, maxBidder);
+ maxBidder send reply;
+ seller send reply
+ } else {
+ seller send AuctionFailed()
+ }
+ receiveWithin(timeToShutdown) {
+ case Offer(_, client) => client send AuctionOver()
+ case TIMEOUT() => running = false
+ }
+
+ }
+ }
+ }
+}
+
+// ---- Test -------------------------------------------------------------
+
+object auction {
+
+ val random = new java.util.Random();
+
+ val minBid = 100;
+ val closing = new Date(new Date().getTime() + 60000);
+
+ val seller = new Actor {
+ override def run() = {}
+ }
+ val auction = new Auction(seller, minBid, closing);
+
+ def client(i: int, increment: int, top: int) = new Actor {
+ val name = "Client " + i;
+ def log(msg: String) = Console.println(name + ": " + msg);
+ var running = true;
+ var max: int = _;
+ var current: int = 0;
+ override def run() = {
+ log("started");
+ auction send Inquire(this);
+ receive {
+ case Status(maxBid, _) => {
+ log("status(" + maxBid + ")");
+ max = maxBid
+ }
+ }
+ while (running) {
+ if (max >= top)
+ log("too high for me")
+ else if (current < max) {
+ current = max + increment;
+ Thread.sleep(1 + random.nextInt(1000));
+ auction send Offer(current, this);
+ }
+ receive {
+ case BestOffer() => {
+ log("bestOffer(" + current + ")");
+ }
+ case BeatenOffer(maxBid) => {
+ log("beatenOffer(" + maxBid + ")");
+ max = maxBid;
+ }
+ case AuctionConcluded(seller, maxBidder) => {
+ log("auctionConcluded");
+ }
+ case AuctionOver() => {
+ running = false;
+ log("auctionOver");
+ }
+ }
+ }
+ }
+ }
+
+ def main(args: Array[String]) = {
+ seller.start();
+ auction.start();
+ client(1, 20, 200).start();
+ client(2, 10, 300).start();
+ }
+
+}