a dangling reference.
      </p>
<p>
        <span class="bold"><strong><span class="emphasis"><em>If in doubt, do not ever mix expression templates
        with the auto keyword.</em></span></strong></span>
      </p>
</td></tr>
</table></div>
<p>
      And finally... the performance improvements from an expression template library
      like this are often not as dramatic as the reduction in number of temporaries
      would suggest. For example if we compare this library with <a href="http://math.berkele