Module SuccNat2Pos.
(** Composition of [Pos.of_succ_nat] and [Pos.to_nat] is successor on [nat] *)
(** [Pos.of_succ_nat] is hence injective *)

Lemma inj_iff (n m : nat) : Pos.of_succ_nat n = Pos.of_succ_nat m <-> n = m.