title: What does operator void* () mean?
body: <p>I googled, but didn't find a clear answer. Example:</p>
  
  <pre><code>class Foo {
  public:
      operator void* () {
           return ptr;
      }
  
  private:
      void *ptr;
  };
  </code></pre>
  
  <p>I understand what <code>void* operator()</code> is. Is the above operator the same thing in a different syntax? If not, what is it? And how can I use that operator to get the <code>ptr</code>?</p>