title: Use STL to populate a vector<T> from map<T,Z>'s keys
body: <pre><code>map&lt;T,Z&gt; m= ...;
  vector&lt;T&gt; v;
  v.reserve(m.size);
  for(map&lt;T,Z&gt;::iterator it=m.begin();it!=m.end();++it)
  {
   v.push_back(it-&gt;first);
  }
  </code></pre>
  
  <p>Is there a nicer 1-line version using some STL function(s)?</p>
  
  <p><strong>edit: <em>not</em> using c++11!</strong></p>