(** Old-style rich specification by proof of existence *)

  Inductive Zdiv_rest_proofs (x:Z) (p:positive) : Set :=
    Zdiv_rest_proof :
    forall q r:Z,
      x = q * two_power_pos p + r ->
      0 <= r -> r < two_power_pos p -> Zdiv_rest_proofs x p.(** Old-style rich specification by proof of existence *)

  Inductive Zdiv_rest_proofs (x:Z) (p:positive) : Set :=
    Zdiv_rest_proof :
    forall q r:Z,
      x = q * two_power_pos p + r ->
      0 <= r -> r < two_power_pos p -> Zdiv_rest_proofs x p.

Lemma Zdiv_rest_ok x p : let (q,r) := Zdiv_rest x p in x = q * 2^(Zpos p) + r /\ 0 <= r < 2^(Zpos p).