interface ihello
{
  in void hello();
  out void cruel();
  out void world();

  behaviour
  {
    bool idle = true;
    [idle] on hello: idle = !idle;
    [!idle] {
      on hello: illegal;
      on inevitable: {idle = !idle; cruel;}
      on inevitable: {idle = !idle; world;}
    }
  }
}

component async_nondet
{
  provides ihello h;

  behaviour
  {
    requires dzn.async i;

    bool idle = true;
    [idle] on h.hello(): {idle = !idle; i.req();}
    [!idle] {
      on i.ack(): {idle = !idle; h.cruel();}
      on i.ack(): {idle = !idle; h.world();}
    }
  }
}