BackwardOp</span></tt></td>
<td>Binary <a class="reference internal" href="./lambda-expression.html">Lambda Expression</a></td>
<td>The operation to be executed on backward
traversal.</td>
</tr>
<tr><td><tt class="literal"><span class="pre">ForwardOp</span></tt></td>
<td>Binary <a class="reference internal" href="./lambda-expression.html">Lambda Expression</a></td>
<td>The operation to be executed on forward
traversal.</td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="id523">
<h3><a class="subsec