Member functions for derived information in a class

Question

While designing an interface for a class I normally get caught in two minds whether should I provide member functions which can be calculated / derived by using combinations of

Answer 1

I think this is perfectly valid if the method:

• fits in the class responsibilities
• is not too specific to a small part of the class clients (like at least 20%)

This is especially true if the method contains complex logic/computation that would be more expensive to maintain in many places than only in the class.