interface ITwotopon
{
  in void e();
  in void t();
  out void a();
  behaviour
    {
      bool b = false;
      on e: [b] { a; }
      on e: [!b] { a; }
      on t: [!b] { a; }
    }
}

component Twotopon
{
  provides ITwotopon i;

  behaviour
    {
      bool b = false;
      on i.e(): [b] { i.a(); }
      on i.e(): [!b] { i.a(); }
      on i.t(): i.a();
    }
}