proposition: Lemma leIxl x y z : y <= x -> y `&` z <= x.
proof: Proof. by rewrite !leEmeet meetAC => /eqP ->. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)