It is an old concept that got ignored somewhere along the road to java. Inheritance for the sake of implementation is called WAS_A. In C++, this is what private

It is an old concept that got ignored somewhere along the road to java. Inheritance for the sake of implementation is called WAS_A. In C++, this is what private inheritance does. In languages like Java and Ruby, WAS-A is often implemented using delegation, so that a square HAS-A rectangle.