title: How to update such map structure?
body: <p>I have a <code>std::map&lt;boost::shared_ptr&lt;some_class&gt;, class_description&gt; class_map;</code> where <code>class_description</code> is: </p>
  
  <pre><code>//Each service provides us with rules
  struct class_description
  {
      //A service must have
      std::string name;
              // lots of other stuff...
  };
  </code></pre>
  
  <p>and I have another <code>std::map&lt;boost::shared_ptr&lt;some_class&gt;, class_description&gt; class_map_new;</code></p>
  
  <p>I need to insert pairs <code>&lt;boost::shared_ptr&lt;some_class&gt;, class_description&gt;</code> from <code>class_map_new</code> to <code>class_map</code> in case there was no <code>class_description</code> with such <code>name</code> in <code>class_map</code> before. How to do such thing?</p>