interface I
{
  in void a();
  out void b();
  out void c();

  behaviour
  {
    bool t = false;
    on a:
      {
        if (t)
        {
          b;
        }
        else
        {
          c;
        }
        t = !t;
      }
  }
}

component If
{
  provides I i;
  behaviour
  {
    bool t = false;
    on i.a():
      {
        if (t)
        {
          i.b();
        }
        else
        {
          i.c();
        }
        t = !t;
      }
  }
}