Past exam of the year 1 of the computer science course of the University of Oxford / 2016 / Imperative programming / 6 / b / Solution

Programming language polymorphism permits one interface or piece of code to work with values of several types, while providing the behavior appropriate to those values. For example a routine that calls play through a Player reference can use a Regular, Optimistic, or House object without knowing its concrete software class.

Use programming language polymorphism when clients should depend on a common contract while concrete behavior varies, or when an algorithm is independent of the element type. It avoids duplicating client logic or repeatedly inspecting concrete runtime types, and supports extensions behind the same interface. A shared interface must still have meaningful behavioral guarantees: merely giving unrelated operations the same name does not establish that implementations can safely replace one another.