(** Boolean equality *)
Definition bbeq (ab1 ab2: ablock) : bool :=
eq_aptr ab1.(ab_summary) ab2.(ab_summary) &&
ZTree.beq (fun c1 c2 => proj_sumbool (eq_acontent c1 c2)) ab1.(ab_contents) ab2.(ab_contents).

Lemma bbeq_load:
forall ab1 ab2,
bbeq ab1 ab2 = true ->
ab1.(ab_summary) = ab2.(ab_summary)
/\ (forall chunk i, ablock_load chunk ab1 i = ablock_load chunk ab2 i).