protected

In C++, I can't think of a case in which I would like to inherit private/protected from a base class: class Base; class Derived1 : private Base; class Derived2 : protected Base; Is it really useful? It is useful when you want to have access to some members of the base class, but without exposing them in your class interface. Private inheritance can also be seen as some kind of composition: the C++ faq-lite gives the following example to illustrate this statement class Engine { public: Engine(int numCylinders); void start(); // Starts this Engine }; class Car { public: Car() : e_(8) { } //

This code: abstract class C { protected abstract void F(D d); } class D : C { protected override void F(D d) { } void G(C c) { c.F(this); } } Generates this error: Cannot access protected member 'C.F(D)' via a qualifier of type 'C'; the qualifier must be of type 'D' (or derived from it) What in the world were they thinking? (Would altering that rule break something?) And is there a way around that aside from making F public? Edit: I now get the reason for why this is (Thanks Greg ) but I'm still a bit perplexed as to the rational; given: class E : C { protected override void F(D d) { } } Why