title: C++ templates Turing-complete?
body: <p>I'm told that the template system in C++ is Turing-complete at compile time. This is mentioned in <a href="https://stackoverflow.com/questions/75538/hidden-features-of-c#75627">this post</a> and also on <a href="http://en.wikipedia.org/wiki/C%2B%2B" rel="noreferrer">wikipedia</a>.</p>
  
  <p>Can you provide a nontrivial example of a computation that exploits this property?</p>
  
  <p>Is this fact useful in practice?</p>