class="identifier">domain</span><span class="special">,</span> <span class="identifier">tag</span><span class="special">::</span><span class="identifier">int_</span><span class="special">&gt;</span> <span class="special">:</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span> <span class="special">{};</span>
</pre>
<p>
        </p>
<p>
</p>
<pre class="programlisting"><span class="keyword">template</span> <span class="special">&lt;&gt;</span> <span cl