proposition: Lemma slt_filterR (p : pred A) ks x y : (y \notin ks) || p y -> x <[filter p ks] y -> x <[ks] y.
proof: Proof. by apply: index_filter_ltR. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path interval order) pcm(options prelude ordtype seqext)