proposition: Lemma lexi_pair (x1 y1 : T) (x2 y2 : T') : (x1, x2) <= (y1, y2) :> T * T' = (x1 <= y1) && ((x1 >= y1) ==> (x2 <= y2)).
proof: Proof. by []. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)