proposition: Lemma enc_stack_spec R s t : s/t el R -> FSTeq ⊢ opair (enc_string s) (enc_string t) ∈ enc_stack R.
proof: Proof. induction R as [|[u v] R IH]; cbn; auto. intros [[=]| H]; subst. - apply FST_adj; auto. apply DI1. apply FST_refl'. auto. - apply FST_adj; auto. 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)