Commit 2022-08-11 05:59 60a1dcf7

refactor(set_theory/ordinal/cantor_normal_form): simplify CNF definition (#15449) We simplify the definition of CNF by removing the casing on b = 0. Note that the new definition is not equivalent to the old one: we now have CNF 0 o = [(0, o)] instead of CNF 0 o = []. This is a good thing though, since it means that CNF_foldr (arguably the defining characteristic of the CNF) is now unconditionally true. We generalize previously existing theorems according to this new definition. Note that none of the theorems have had their hypotheses strengthened, but a few have been weakened.