class="identifier">multi_pass</span></code>
        will buffer data when needed and will discard the buffer when its contents
        is not needed anymore. This happens either if only one copy of the iterator
        exists or if no backtracking can occur.
      </p>
<p>
        A grammar must be designed with care if the <code class="computeroutput"><span class="identifier">multi_pass</span></code>
        iterator is used. Any rule that may need to backtrack, such as one that contains
        an alterna