<p>
  In this exercise, you will experiment with <em>type-directed
  programming</em>.
</p>

<p>
  We give you the example program of the lecture in which two type
  definitions have been changed as in the given prelude. A
  case <code>Tired</code> has been added to type <code>state</code>,
  and a case <code>Sleep</code> has been added to
  type <code>action</code>.
  <br/>
  By clicking the <em>typecheck</em> button, you can notice that
  several warnings are issued by the OCaml compiler. Go through the
 