title: Improving efficiency of std::copy() with back_inserter() or inserter()
body: <p><code>back_inserter</code> and <code>insert_iterator</code> are very handy, but they're also very inefficient!</p>
  
  <p>When you're appending <code>char</code>s, for example, there is a great deal of overhead for every element when you're <code>copy</code>ing, when in many situations, there really doesn't need to be.</p>
  
  <p>Is there a way to make them more efficient?</p>