virtual function in private or protected inheritance

Question

It\'s easy to understand the virtual function in public inheritance. So what\'s the point for virtual function in private or protected inheritance?

For example:

Answer 1

• There doesn't need to be a point to every combination of different features. You're simply allowed to combine them.
• A virtual protected member is accessible to derived classes, so it's useful to them.
• A virtual private member is accessible to friend classes, so it's useful to them.