proposition: Theorem spec_leb x y : leb x y = Z.leb (to_Z x) (to_Z y).
proof: Proof. apply Bool.eq_iff_eq_true. rewrite Z.leb_le. unfold Z.le, leb. rewrite spec_compare. now destruct Z.compare; split. Qed.
imports: ZArith Lia BigNumPrelude NSig ZSig