d they should not be used. If they are,
          an <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">illegal_backtracking</span></code> exception will be
          thrown. For all other iterator types this is a no-op. The <code class="computeroutput"><span class="identifier">flush_multi_pass</span></code> generates a parser component
          which always succeeds and which does not consume any input (very much like
          <code c