title: about an example of operator overloading
body: <p>Here are an example of operator overloading from C++ programming language:</p>
  
  <pre><code>struct X{
       int I;
       X(int);
       X operator+(int);
  };
  
  struct Y{
      int I;
      Y(X);
      Y operator+(X);
      operator  int();
  }
  </code></pre>
  
  <p>I am not clear about what does "int I" do in the definitions of both X and Y. Besides, I do not understand how to analyze the functionality of "operator int()" in the definition of X.</p>