proposition: Lemma index_enum_ord (n : nat) (i : 'I_n) : index i (enum 'I_n) = i.
proof: Proof. by rewrite enum_ord index_enum_ord. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)