Are type fields pure evil?

Question

As discusses in The c++ Programming Language 3rd Edition in section 12.2.5, type fields tend to create code that is less versatile, error-prone, less intuitive, and less maintai

Answer 1

The best example I can think of (and the one I've run into before), is when your set of types is fixed and the set of functions you want to do (that depend on those types) is fluid. That way, when you add a new function, you modify a single place (adding a single switch) rather than adding a new base virtual function with the real implementation scattered all across the classes in your type hierarchy.