title: Is std::pair<int, std::string> ordering well-defined?
body: <p>It seems that I can sort a <code>std::vector&lt;std::pair&lt;int, std::string&gt;&gt;</code>, and it will sort based on the int value. Is this a well defined thing to do?</p>
  
  <p>Does <code>std::pair</code> have a default ordering based on its elements?</p>