proposition: Lemma in_hd_tl X n (v : vec X (S (S n))) : Vector.In (Vector.hd (Vector.tl v)) v.
proof: Proof. apply (Vector.caseS' v). intros ? w. apply (Vector.caseS' w). constructor. constructor. 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