.com/tech/stl/RandomAccessIterator.html">RandomAccessIterator</a></cite>,
          <code>x1 - x2</code> with return convertible to <code>D</code> is
          also required.
        </td>
      </tr>
    </table>

    <h4><a name="iterator_helpers_notes">Iterator Helper Notes</a></h4>

    <p><a name="1">[1]</a> Unlike other iterator helpers templates,
    <code>output_iterator_helper</code> takes only one template parameter -
    the type of its target class. Although to some it might seem like an
    unn