title: Error binding 'string&' to 'const string' when dereferencing a set iterator
body: <p>I'm using C++11 and STL. I have this piece of code:</p>
  
  <pre><code>std::set&lt;std::string&gt;::iterator it;
  [...]
  std::string &amp;str = *it;
  </code></pre>
  
  <p>Compiler throws this error:</p>
  
  <blockquote>
    <p>error: binding reference of type ‘std::__cxx11::string&amp; {aka std::__cxx11::basic_string&amp;}’ to ‘const std::__cxx11::basic_string’ discards qualifiers</p>
  </blockquote>
  
  <p>Why is it happening?</p>