(** Results about id injections*)
Definition id_ren m :=
fun b => if is_left (valid_block_dec m b) then Some b else None.
Hint Unfold id_ren.

Lemma is_id_ren :
forall f m
(Hdomain: domain_memren f m)
(Hf_id: forall b1 b2, f b1 = Some b2 -> b1 = b2),
f = id_ren m.