proposition: Lemma le_trans : transitive Rle.
proof: Proof. by move=> y x z; rewrite !le_def' => /predU1P [->|hxy] // /predU1P [<-|hyz]; rewrite ?hxy ?(lt_trans hxy hyz) orbT. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)