proposition: Lemma lex0 x : (x <= \bot) = (x == \bot).
proof: Proof. by rewrite le_eqVlt (le_gtF (le0x _)) orbF. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)