interface ihello
{
  in void hello();

  behaviour
  {
    on hello: {}
  }
}

component hello_expression
{
  provides ihello h;
  requires iworld w;

  behaviour
  {
    bool b = false;
    [0 == 0] on h.hello(): w.world();
    [0 == 1] on h.hello(): b = !b;
  }
}

interface iworld
{
  in void world();

  behaviour
  {
    on world: {}
  }
}