nt">// set vlevel</span>
<a name="l00183"></a>00183   <span class="keyword">virtual</span> <span class="keywordtype">void</span> set_vlevel(<span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> vlevel) = 0;
<a name="l00184"></a>00184 
<a name="l00185"></a>00185   <span class="comment">// get vlevel</span>
<a name="l00186"></a>00186   <span class="keyword">virtual</span> <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> vlevel() <span class="keyword">cons