  'a * 'a  -> unit
	val fail :     'a * exn -> unit

	val isHole :   'a -> bool
    end
  </PRE>

<?php section("description", "description") ?>

  <DL>
    <DT>
      <TT>exception Hole</TT>
    </DT>
    <DD>
      <P>Raised on any attempt to access a hole, and on any attempt to
      pass a non-hole to any of the functions in this structure.</P>
    </DD>

    <DT>
      <TT>hole ()</TT>
    </DT>
    <DD>
      <P>Creates a new hole and an associated future. Returns the
      hole.</P>
    </DD>

    <D