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