interface starter
{
  in void start_and_wait ();
  behavior
  {
    on start_and_wait: {}
  }
}

interface runner
{
  in void start ();
  out void finished ();
  behavior
  {
    bool running = false;
    on start: running = true;
    [running] on inevitable: {running = false; finished;}
  }
}

component join
{
  provides blocking starter ref;
  requires runner one;
  requires runner two;

  behavior
  {
    subint Runners {0..2};
    Runners running = 0;

    blocking on ref.start_and_wait ():
      {running = 2; one.start(); two.start ();}
    [running != 1] on one.finished (), two.finished ():
      running = running - 1;
    [running == 1] on one.finished (), two.finished ():
      {running = 0; ref.reply ();}
  }
}