mpty() <span class="keyword">const</span> = 0;
<a name="l00302"></a>00302 
<a name="l00303"></a>00303   <span class="comment">// clear all context</span>
<a name="l00304"></a>00304   <span class="keyword">virtual</span> <span class="keywordtype">bool</span> clear() = 0;
<a name="l00305"></a>00305 
<a name="l00306"></a>00306   <span class="comment">// change the internal state to output next-optimal output.</span>
<a name="l00307"></a>00307   <span class="comment">// calling it n-th times, can get n-best res