title: template< template <typename> something_else >, what is this?
body: <p>I'm just starting learning C++11 and I never saw this syntax in the list of new features:</p>
  
  <pre><code>template &lt;template &lt;typename&gt; class F&gt;
  struct fun;
  </code></pre>
  
  <p>what is it and how does it work?</p>