Implementing relationships using Affinity

OO languages typically provide one form of object equality, known as reference equality, where two objects are equal only if they are the same object; two objects which are structurally identical are not considered equal. Thus, programmers who require a more refined notion of equality must define their own operator. Programmer-implemented equality operators tend to rely on informal notions of partial and temporal object immutability which are prone to error. This is a particular problem for objects used in collections which depend on equality. This paper discusses Affinity: an untyped, object-oriented language with a powerful equality operator based on EGAL [2] and support for object-keying and immutability. Affinity is designed to provide coherent and elegant support for object equality, reducing programmer burden and error potential.