title: What is the return value of map::begin() for an empty map?
body: <p>I use something like this:</p>
  
  <pre><code>map&lt;string, Data&gt;::iterator it  = mymap-&gt;begin();
  map&lt;string, Data&gt;::iterator end = mymap-&gt;end();
  
  while (it != end) {
      // do stuff
      ++it;
  }
  </code></pre>
  
  <p>I was just wondering if this would work even if the map is empty.
  I couldn't find any information about the return of map::begin() if the map ist empty.</p>