title: How to use std::nested_exception and friends?
body: <p>I've noticed that there are a few more interesting declarations in <code>&lt;exception&gt;</code> in C++11. Can anybody shed any light on what they mean and how to use them?</p>
  
  <p>The ones I'm wondering about are:</p>
  
  <ol>
  <li><code>::std::nested_exception</code></li>
  <li><code>::std::throw_with_nested</code></li>
  <li><code>::std::rethrow_if_nested</code></li>
  </ol>
  
  <p>Additionally, while they seem self-explanatory, it might be nice to know how these worked:</p>
  
  <ol>
  <li><code>::std::exception_ptr</code></li>
  <li><code>::std::make_exception_ptr</code></li>
  <li><code>::std::current_exception</code></li>
  <li><code>::std::rethrow_exception</code></li>
  </ol>