proposition: Lemma sle_sorted ks x y : sorted ord ks -> y \in ks -> x <=[ks] y -> oleq x y.
proof: Proof. by rewrite oleq_eqVord; apply/sle_sorted_lt/trans. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path interval order) pcm(options prelude ordtype seqext)