title: what is the Big O( ) order of std::queue::size?
body: <p>The <code>std::queue</code> class is unclear as to the complexity of the <code>size</code> member function. It appears to be based on the data structure implementation used at the time.</p>
  
  <p>One would <em>assume</em> that <code>size</code> would be <code>O(C)</code>, but it's totally possible for it to be <code>O(N)</code>. Obviously, I can keep my own size, but I would rather just call <code>size</code>.</p>
  
  <p>(Question modified): since <code>deque</code> is the default container, what is O ( ) of std::deque::size()?</p>