an> <span class="special">=</span> <span class="identifier">unused_type</span><span class="special">,</span>
    <span class="keyword">typename</span> <span class="identifier">Char</span> <span class="special">=</span> <span class="keyword">char</span>
<span class="special">&gt;</span>
<span class="keyword">class</span> <span class="identifier">token_def</span><span class="special">;</span>
</pre>
<div class="variablelist">
<p class="title"><b>where:</b></p>
<dl class="variablelist">
<dt><span class="term">