exactly the same point
      in the code where it was suspended before. With a stackless coroutine, only
      the top-level routine may be suspended. Any routine called by that top-level
      routine may not itself suspend. This prohibits providing suspend/resume operations
      in routines within a general-purpose library.
    </p>
<h4>
<a name="coroutine.intro.h5"></a>
      <span class="phrase"><a name="coroutine.intro.first_class_continuation"></a></span><a class="link" href="intro.html#coroutine.int