protected inheritance

Question

Why protected and private inheritance are defined and proposed? I understand some cases private inheritance could be used but it is not recommended. How about protected inheritance?

Can anyone offer me an situation in which protected inheritance is a choice?

I rarely see this.

Thanks so much!

Answer 1

Private inheritance is usually used for mixins---where people inherit to get functionality from the base class, rather than because of "is-a" inheritance.

Protected inheritance can also be used for mixins, where the mixed-in functionality is to be available to downstream classes too.