proposition: Lemma nth_ord_enum (i0 i : 'I_n) : nth i0 (enum 'I_n) i = i.
proof: Proof. by apply: val_inj; apply: nth_enum_ord. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(path div)