proposition: Lemma one_step_union_assoc : forall l r, one_step (union _ (union _ R1 R2) R3) r l <-> one_step (union _ R1 (union _ R2 R3)) r l.
proof: Proof. intros l r. apply one_step_equiv. clear. intros l r. rewrite union_assoc. reflexivity. Qed.
imports: Coq(Relations List Setoid) CoLoR(weaved_relation closure equational_theory_spec dp modular_dp terminaison)