proposition: Lemma diffxx x : x `\` x = \bot.
proof: Proof. by have := diffKI x x; rewrite meet_r. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)