If SortedList has exactly the same public interface as List, is SortedList a kind-of List?
Probably not. The most important insight is that the answer depends on the details of the base class’s contract. It is not enough to know that the public interfaces / method signatures are compatible; one also needs to know if the contracts / behaviors are compatible. The important part of the previous sentence are the words “contracts / behaviors.” That phrase goes well beyond the public interface = method signatures = method names and parameter types and constness. A method’s contract means its advertised behavior = advertised requirements and promises = advertised preconditions and postconditions.
