proposition: Lemma joinKI y x : meet x (join x y) = x.
proof: Proof. by rewrite /meet /join f'_can joinKI f_can. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)