proposition: Lemma diffx0 x : x `\` \bot = x.
proof: Proof. by apply/eqP; rewrite eq_diff join0x meetx0 lexx eqxx. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)