proposition: Lemma meet_idPl {x y} : reflect (x `&` y = x) (x <= y).
proof: Proof. by rewrite leEmeet; apply/eqP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)