(** ** BPCP reduces to iBPCP *)
Definition card_eq : forall x y : card bool, {x = y} + {x <> y}.

Lemma itau_tau2 P A : A <<= P -> itau2 P (f P A) = tau2 A.
Definition g (P : BSRS) (A : list nat) := map (fun n => nth n P ( [] / [] )) A.