title: Private method in a C++ interface?
body: <p>Why would I want to define a C++ interface that contains private methods?</p>
  
  <p>Even in the case where the methods in the public scope will technically suppose to act like template methods that use the private methods upon the interface implementation, even so, we're telling the technical specs. right from the interface.</p>
  
  <p>Isn't this a deviation from the original usage of an interface, ie a public contract between the outside and the interior?</p>
  
  <p>You could also define a friend class, which will make use of some private methods from our class, and so force implementation through the interface. This could be an argument.</p>
  
  <p>What other arguments are for defining a private methods within an interface in C++?</p>