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