(** * The sign function *)
Definition sign (x : R) :=
match total_order_T 0 x with
| inleft (left _) => 1
| inleft (right _) => 0
| inright _ => -1
end.

(** Notations *)
Lemma SSR_leq (n m : nat) : is_true (ssrnat.leq n m) <-> (n <= m)%nat.