proposition: Lemma subst_shift {ff : falsity_flag} (phi : form) s : phi[↑][s..] = phi.
proof: Proof. rewrite subst_comp. apply subst_id. now intros [|]. Qed.
imports: Undecidability.Synthetic(Definitions DecidabilityFacts EnumerabilityFacts ListEnumerabilityFacts ReducibilityFacts) Undecidability(Shared.ListAutomation Shared.Dec) Coq(Eqdep_dec PeanoNat Nat) Coq.Vectors.Vector Undecidability.Shared.Libs.PSL.Vectors(Vectors) EqdepFacts