Given Alexander's premise, I agree with your response. But his premise is wrong. Python's current builtin set class maps abstract equivalence classes to representative members. And this *is* useful. Mapping arbitrary members of such classes to representative members, sometimes called 'canonical', is a standard problem/goal in math. String interning is an application of this idea.
Right. However, this is conceptually a function. In some cases (like string interning), it is mutable (over time) and finite (at any point in time). We already have a data type that can perfectly represent mutable finite funcitons, namely dictionaries. And indeed, interning is implemented by a dictionary. What Alexander wants is that the set type also becomes useful for storing canonical representations. I find that inappropriate, since dicts already provide the one obvious way to do it. Regards, Martin