proposition: Lemma max_idPl x y : reflect (max x y = x) (y <= x).
proof: Proof. exact: comparable_max_idPl. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)