fact: Definition enum_rank_in x0 A (Ax0 : x0 \in A) x := insubd (Ordinal (@enum_rank_subproof _ x0 A Ax0)) (index x (enum A)).
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)