t
    in its type. <I>Filling</I> a hole globally replaces the hole with a value.
    Unlike a <EM>future</EM>, accessing a hole does not imply synchronization,
    but causes the exception <TT>Hole</TT> to be raised (this includes calls to
    <TT>Future.status</TT>). It is possible to extract a future from
    a hole, though.
  </P>

  <P>
    <B>The use of the <TT>Hole</TT> structure is strongly discouraged!</B>
    For most tasks, <A href="promise.html"><TT>Promise</TT></A> is the
    prefarable choice,