proposition: Lemma eq_chain_test : forall x1 x2 x3 x4 s1 s2 s3 s4, Empty s1 -> In x2 (add x1 s1) -> In x3 s2 -> ~ In x3 (remove x2 s2) -> ~ In x4 s3 -> In x4 (add x3 s3) -> In x1 s4 -> Subset (add x4 s4) s4.
proof: Proof. fsetdec. Qed.
imports: Decidable Setoid DecidableTypeEx MSetFacts