title: STL map stores searched keys
body: <p>I have just found out that when I search a map like :</p>
  
  <pre><code>  std::map&lt;std::string, int&gt; aMap;
  </code></pre>
  
  <p>the keys I search start to be part of the map. In the case above the values are stored as zeros. In case of pointers it stores the values as 0 valued pointers</p>
  
  <p>I am doing the search with the [] operator, like in :</p>
  
  <pre><code>  int a = aMap["some key"];
  </code></pre>
  
  <p>Can you confirm this ? I think I have misinterpreted the [] operator. Is it doing an assignment ?!</p>
  
  <p>Where can I find STL documentation of these kind of "features" ?</p>