t">expr</code></span></p></td>
<td><p>The terminal expression node. </p></td>
</tr></tbody>
</table></div></td>
</tr>
<tr>
<td><p><span class="term">Requires:</span></p></td>
<td>
<p>
                  <code class="computeroutput"><a class="link" href="../is_expr.html" title="Struct template is_expr">proto::is_expr</a>&lt;Expr&gt;::value</code> is
                  <code class="computeroutput">true</code>
                </p>
<p>
                  <code class="computeroutput">0 == Expr::proto_arity::value</