Changing some default template parameters
<p>Consider a template class like this:</p>

<pre><code>template &lt;int opt1 = 1,
          bool opt2 = false,
          bool opt3 = true,
          int opt4 = 50&gt;
class X  { };
</code></pre>

<p>I try to change just one parameter, but it seems that C++ can't do that. Or am I wrong? How to achieve something like this:</p>

<pre><code>X&lt;opt2 = true&gt; x;
</code></pre>
