title: Why does std::pair expose member variables?
body: <p>From <a href="http://www.cplusplus.com/reference/utility/pair/" rel="noreferrer">http://www.cplusplus.com/reference/utility/pair/</a>, we know that <code>std::pair</code> has two member variables, <code>first</code> and <code>second</code>.</p>
  
  <p>Why did the STL designers decide to expose two member variables, <code>first</code> and <code>second</code>, instead of offering a <code>getFirst()</code> and a <code>getSecond()</code>?</p>