When to use C++ private inheritance over composition?

Question

Can you give me a concrete example when is preferable to use private inheritance over composition? Personally, I will use composition over private inheritance, but there might be the case that using private inheritance is the best solution for a particular problem. Reading the C++ faq, gives you an example on using private inheritance, but I seems easier to use composition + strategy pattern or even public inheritance than private inheritance.

Answer 1

Scott Meyers in "Effective C++" item 42 says

"Only inheritance gives access to protected members, and only inheritance allows for virtual functions to be redefined. Because virtual functions and protected members exist, private inheritance is sometimes the only practical way to express an is-implemented-in-terms-of relationship between classes."