C++ FAQs, Second Edition

Chapter 37. Private and Protected Inheritance

FAQ 37.01 What are private inheritance and protected inheritance?

Has-a, not is-a. From the user's perspective, private and protected inheritance are semantically similar to composition, but they are very different from normal public inheritance. Thus private and protected inheritance are a lot more like “has-a” than “is-a” (more precisely, than “is-substitutable-for”). Here are the ways they are like “has-a”.

Like normal composition, private and protected inheritance cause an inner object to be contained inside the outer object. With normal composition, this inner object is called a member object. The syntax for doing this with private inheritance is different than the syntax for normal composition, ...