proposition: Lemma app_eq_nil_iff : forall {A} s1 s2, @nil A = s1 ++ s2 <-> ([] = s1 /\ [] = s2).
proof: Proof. intros; split; intro H. - symmetry in H; apply app_eq_nil in H; intuition. - intuition; subst; intuition. Qed.
imports: Fiat.Common.Coq__8_4__8_5__Compat Coq.ZArith.ZArith Coq.Lists.List Coq.Lists.SetoidList Coq.Bool.Bool Fiat.Common Fiat.Common.List.Operations Fiat.Common.Equality Fiat.Common.List.FlattenList Fiat.Common.LogicFacts