proposition: Lemma leU2l_le y t x z : x `&` t = \bot -> x `|` y <= z `|` t -> x <= z.
proof: Proof. by move=> xIt0 /(leI2 (lexx x)); rewrite joinKI meetUr xIt0 joinx0 leIidl. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)