Feels like an API that was backed by lazy cons lists like Haskell's would give you actual circular lists for free here.

▲ Jaxan 5 days ago | parent [-]

It would still have a beginning. And it would not be “for free” as the used/seen part of the data structure would remain in memory.

	▲	whateveracct 5 days ago \| parent [-]
		The list in memory would not have duplicates (which this one seems to have) because the list itself would be cyclical. It could be infinite in both directions. That's just a zipper or `([a], a, [a])`