proposition: Lemma sleNgt ks t1 t2 : t1 <=[ks] t2 = ~~ t2 <[ks] t1.
proof: Proof. by rewrite sltNge negbK. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path interval order) pcm(options prelude ordtype seqext)