proposition: Lemma lteifN C x y : x < y ?<= if ~~ C -> ~~ (y < x ?<= if C).
proof: Proof. by case: C => /=; case: comparableP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)