proposition: Lemma diff0x x : \bot `\` x = \bot.
proof: Proof. by apply/eqP; rewrite eq_diff joinx0 meet0x lexx eqxx le0x. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)