proposition: Lemma subR_ge0 x y : (0 <= y - x) <-> (x <= y).
proof: Proof. split => [|?]; first by move/leR_subr_addr; rewrite add0R. by apply/leR_subr_addr; rewrite add0R. Qed.
imports: mathcomp(all_ssreflect ssralg ssrnum) Reals mathcomp(lra) mathcomp(Rstruct)