ass=keyword>const</span>; <span class="comment">// convertible to a bool</span>
    <span class=keyword>    int         </span><span class=identifier>length</span><span class=special>() </span><span class=keyword>const</span>;
        <span class="keyword">bool</span>        has_valid_attribute<span class="special">()</span> <span class="keyword">const</span><span class="special">;</span>
   <span class=keyword>    </span> <span class=identifier>void</span><span class=special>        </span><span class=iden