ch
</span><span class=keyword>    </span><span class=special>{
</span><span class=keyword>    public</span><span class=special>:

    </span><span class=keyword>    </span><span class=comment>/*...*/

</span><span class=special>    </span><span class=keyword>    typedef</span><span class="identifier"> T attr_t</span><span class="special">;<br>
             </span><span class=keyword>    </span><span class="special">   </span><span class=keyword>operator safe_bool</span><span class=special>() </span><span cl