proposition: Lemma contains_app A B T : A ⊏ T -> B ⊏ T -> (A ++ B) ⊏ T.
proof: Proof. intros ? ? ? [] % in_app_or; auto with contains_theory. Qed.
imports: Undecidability.FOL.Syntax(Core Facts) Undecidability.Synthetic(Definitions DecidabilityFacts EnumerabilityFacts ListEnumerabilityFacts ReducibilityFacts) Undecidability(Shared.ListAutomation) Undecidability(Shared.Libs.PSL.Vectors.Vectors) Coq.Setoids.Setoid Arith Lia List