classifying a heritage

Question

I have an exam coming up in the near future and I'm really stuck on a question that I couldn't find any answers on.

Suppose that a class CI inherits class Sup as:

class CI: protected Sup
{};

Why is this not a classifying heritage?

Thanks in advance and I appreciate all help.

http://www.parashift.com/c++-faq/prot-vs-priv-inherit.html – Alex Jan 16 '13 at 15:25 — Alex, Jan 16 '13 at 15:25
First time I see the word "classifying inheritance"... – Stephane Rolland Jan 16 '13 at 15:27 — Stephane Rolland, Jan 16 '13 at 15:27

score 4 · Accepted Answer · edited May 23 '17 at 10:34

In C++, only public inheritance is deemed as real inheritance, which means a subclass will inherit the interface of its superclass(i.e IS-A relationship). A decent inheritance should satisfy Liskov substitution principle.

As for protected/private inheritance, they're actually kind of containment/composition, for a derived class will hide its base class's interface(as protected/private member) and only make use of base class's implementation(i.e. HAS-A or Is-Implemented-In-Terms-Of relationship).

You may refer to this question on SO for better understanding: Why do we actually need Private or Protected inheritance in C++?

That said, protected/private inheritance is an arguable feature in C++, which is abandoned by C++ successors like Java and C#.

classifying a heritage

1 Answers1