proposition: Lemma sltL x y ks : x <[x :: ks] y = (y != x).
proof: Proof. by rewrite slt_cons eq_refl andbT. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path interval order) pcm(options prelude ordtype seqext)