proposition: Lemma enc_stack_subst sigma B : (enc_stack B)`[sigma] = enc_stack B.
proof: Proof. induction B as [|[s t] B IH]; cbn; trivial. rewrite IH. unfold enc_string. now rewrite !prep_string_subst. Qed.
imports: Undecidability.FOL.Syntax.Facts Undecidability.FOL.Semantics.Tarski.FullFacts Undecidability.FOL.Deduction.FullNDFacts Undecidability.FOL.Sets.FST Undecidability.FOL.FST Undecidability.FOL.Reductions.PCPb_to_FST Undecidability.PCP(PCP Util.PCP_facts Reductions.PCPb_iff_dPCPb) Undecidability(Shared.ListAutomation)