="identifier">is_string</span></code>
                    needs to behave as if if was a <a href="../../../../../../../libs/mpl/doc/refmanual/integral-constant.html" target="_top">MPL
                    Boolean Constant</a>.
                  </p>
                </td>
</tr></tbody>
</table></div>
<h6>
<a name="spirit.advanced.customize.is_string.h6"></a>
          <span class="phrase"><a name="spirit.advanced.customize.is_string.predefined_specializations"></a></span><a class="link" href="is_string.html#s