proposition: Lemma zero_correct : convert zero = Interval.Ibnd (Xreal 0) (Xreal 0).
proof: Proof. simpl. rewrite F'.valid_lb_zero, F'.valid_ub_zero. now rewrite F.zero_correct. Qed.
imports: Coq(Bool Reals Psatz) Flocq(Raux) Stdlib Xreal Basic Sig Interval