interface ihello {
  in void hello();
  out void world();
  behaviour {
    bool b = true;
    on hello: { b = !b; }
    [b] on inevitable: world;
  }
}

component hello_single_to_multiple {
  provides ihello h;
  requires ihello w;
  behaviour {
    on h.hello(): { w.hello(); }
    on w.world(): { h.world(); h.world(); }
  }
}