title: BOOST_FOREACH and a vector
body: <p>I have a vector of Scenes, <code>vector&lt;Scene&gt;</code>. What is the correct way to iterate over the elements, as reference or not?</p>
  
  <p>For example this:</p>
  
  <pre><code>BOOST_FOREACH(Scene scene, mScenes)
  {
         .....
  }
  </code></pre>
  
  <p>Does the macro copy the Scene for each iteration over the vector, or does it use a reference behind the scenes?</p>
  
  <p>So is it any different from this:</p>
  
  <pre><code>BOOST_FOREACH(Scene&amp; scene, mScenes)
  {
         .....
  }
  </code></pre>