ken attribute will be generated from the matched input  </span>
<span class="comment">// sequence every time it is requested. But as soon as you specify at </span>
<span class="comment">// least one token attribute type you'll have to list all attribute types </span>
<span class="comment">// used for token_def&lt;&gt; declarations in the token definition class above, </span>
<span class="comment">// otherwise compilation errors will occur.</span>
<span class="keyword">typedef</span> <span class="identifier"