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(* 02110-1301 USA                                                     *)
Require Export DistributedReferenceCounting.machine4.invariant0.
Require Export DistributedReferenceCounting.machine4.invariant1.
Require Export DistributedReferenceCounting.machine4.invariant2.
Require Export DistributedReferenceCounting.machine4.invariant3.
Require Export DistributedReferenceCounting.machine4.invariant4.
Unset Standard Proposition Elimination Names.
(* changes: only a few changes in ancestor_not_reflexive for transition  6 ,  where n0->n1, n1-> n2, n2-> n3. *)
Section INVARIANT6.
Variable c0 : Config.
Fixpoint inc_dec_in_queue (s : Site) (q : queue Message) {struct q} : Prop :=
match q with
| empty => False
| input (inc_dec s2) q' =>
if eq_site_dec s2 s then True else False
| input _ q' => inc_dec_in_queue s q'
end.
(* note that the contrary is not true ! *)

Lemma inc_dec_queue_equal :
forall (q : queue Message) (s1 s2 : Site),
inc_dec_in_queue s1 q -> inc_dec_in_queue s2 q -> s1 = s2.