Dart's isolate test

isolate-test.dart

class Printer extends Isolate {
  main() {
    port.receive((message, replyTo) {
      if (message == null) port.close();
      else print(message);
    });
  }
}

main() {
  // first isolate process
  new Printer().spawn().then((port) {
    for (var message in ['Hello', 'from', 'other', 'isolate']) {
      port.send(message);  
    }
    port.send(null);
  });

  // second isolate process
  new Printer().spawn().then((port) {
    for (var message in ['*Hello', '*from', '*other', '*isolate']) {
      port.send(message);  
    }
    port.send(null);
  });
}

// Results (WTF?)

Hello
from
other
isolate
*Hello
*from
*other
*isolate

// Why the output is sequential but not parallel? How the Dart's processes' scheduler work?

FreakTheMighty, right, it's an anonymous callback function.

kaisellgren, yes, the same I thought (after programming in Erlang and having implemented similar scheduled processes in JS with yield -- https://gist.github.com/1127536). However, after analyzing the source code of Dart's runtime library, I figured out that it's a design decision caused by impossibility of implementation of such parallel processes with using just setTimeout scheduling (you may check btw, my similar setTimeout processes -- https://gist.github.com/1103751). That is, callback process function should run to completeness and can't be interrupted in the middle. And exactly this cases sequential execution, but not parallel.

Recently I discussed the topic in Dart's mailing list: http://bit.ly/n3IUiT

@DmitrySoshnikov: as far as I know, most ES engines do not support yield, except *Monkey. Therefore, I also believe the Dart engineers decided it is not possible to support "parallel processes" in transcompiled JS and this is the outcome :(. By the way, I like https://gist.github.com/1127536, did something similar once as well :)