wordtype">double</span> prob() <span class="keyword">const</span> = 0;
<a name="l00247"></a>00247 
<a name="l00248"></a>00248   <span class="comment">// set token-level penalty. It would be useful for implementing</span>
<a name="l00249"></a>00249   <span class="comment">// Dual decompositon decoding.</span>
<a name="l00250"></a>00250   <span class="comment">// e.g.</span>
<a name="l00251"></a>00251   <span class="comment">// &quot;Dual Decomposition for Parsing with Non-Projective Head Automata&quot;</span