mputeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">istream_iterator</span></code> as is.
        </p></td></tr>
</table></div>
<p>
        Backtracking can be implemented only if we are allowed to save an iterator
        position, i.e. making a copy of the current iterator. Unfortunately, with
        an input iterator, there is no way to do so, and thus input iterators will
        not work with backtracking in <span class="emphasis"><em>Spirit.Qi</em>