On: Why it’s hard for programmers to write a program to flatten a list?

[pcmonk]

To me, "nested list structure" means list-of-lists, which implies a certain natural tree representation, where all elements in a list are siblings.

But maybe I've just been poisoned by Lisp, which tries to use lists as the elusive generic simple data structure.

(OT: https://en.wikipedia.org/wiki/List_of_lists_of_lists)