proposition: Lemma sat_sshift2 (rho : nat -> V) x y z (phi : form) : (z .: y .: x .: rho) ⊨ phi[sshift 2] <-> (z .: rho) ⊨ phi.
proof: Proof. erewrite sat_comp, sat_ext. reflexivity. now intros []. Qed.
imports: Undecidability.FOL.Syntax.Facts Undecidability.FOL.Syntax.Asimpl Undecidability.FOL.Semantics.Tarski.FullFacts Undecidability.FOL.Deduction.FullNDFacts Undecidability.FOL.Sets(binZF ZF) Undecidability.FOL.Reductions.PCPb_to_ZF Undecidability(Shared.ListAutomation) Morphisms Undecidability.FOL(Reductions.PCPb_to_ZFeq)