Hrm. This reminds me of a thought I had about, for the lack of a better term, "groups" in Python. Each data type has a property which is paramount and more or

Hrm. This reminds me of a thought I had about, for the lack of a better term, "groups" in Python. Each data type has a property which is paramount and more or less defines the type. Lists are ordered. The tuple is immutable. The dict is keyed. The set is unique. (But there are some overlaps: dicts are both keyed and their keys are unique.) And I thought, what if you had a group where you could make it immutable or mutable, ordered or not-ordered, where the value was a key to something else (or not), and so on? But then I saw the weird edge cases and the explosions of complexity. Some combinations of these attributes are less appealing than others.