proposition: Lemma eval_plus_inv: forall n m x y z, eval n m (RegExp.plus x y) z -> exists x', exists y', z=x'+y' /\ eval n m x x' /\ eval n m y y'.
proof: Proof. intros. dependent destruction H. eauto. Qed.
imports: ATBR(Common) ATBR(Classes) ATBR(Graph) ATBR(SemiLattice) ATBR(SemiRing) ATBR(KleeneAlgebra) ATBR(MxGraph) ATBR(Reification)