Admitted.

(* Specifications: *)
Theorem S_nbeq_0 : forall n:nat,
beq_nat (S n) 0 = false.
Theorem update_neq' :
forall (d : partial_map) (x y : id) (o: nat),
~ (x = y) -> find x (update d y o) = find x d.
Lemma ascii_256 : forall c, nat_of_ascii c < 256.
Admitted.
Lemma unthree_three_digit (c : ascii) :
let n := nat_of_ascii c in
unthree_digit
(unit_digit (n / 100)) (unit_digit (n / 10)) (unit_digit n)
= Some (ascii_of_nat n).
Lemma read_show_quoted_string : forall (s : string),
read_quoted_string (show_quoted_string s) = Some s.
Lemma read_show_string : forall (s : string),
read_string (show s) = Some s.