its invoker. By contrast, all symmetric coroutines
      are equivalent; one symmetric coroutine may pass control to any other symmetric
      coroutine. Because of this, a symmetric coroutine <span class="emphasis"><em>must</em></span>
      specify the coroutine to which it intends to yield control.
    </p>
<p>
      <span class="inlinemediaobject"><img src="../../../../../libs/coroutine/doc/images/foo_bar_seq.png" align="middle" alt="foo_bar_seq"></span>
    </p>
<p>
      Both concepts are equivalent a