proposition: Lemma up_sshift1 (phi : form') sigma : phi[sshift 1][up (up sigma)] = phi[up sigma][sshift 1].
proof: Proof. rewrite !subst_comp. apply subst_ext. intros []; trivial. cbn. unfold funcomp. now destruct (sigma n) as [|[]]. Qed.
imports: Undecidability.FOL.ZF Undecidability.FOL.Syntax.Facts Undecidability.FOL.Semantics.Tarski.FullFacts Undecidability.FOL.Sets(minZF ZF) Undecidability.FOL.Sets.ZF Undecidability.FOL.Reductions.PCPb_to_ZF Undecidability(Shared.ListAutomation)