proposition: Lemma star_plus_but_one: forall a b: regex, (plus_but_one a b) # == (a + b)#.
proof: Proof. intros. unfold plus_but_one; RegExp.destruct_tests; fold_regex. rewrite star_plus_one. reflexivity. rewrite plus_com. rewrite star_plus_one. reflexivity. reflexivity. Qed.
imports: ATBR(Common) ATBR(Classes) ATBR(Graph) ATBR(SemiLattice) ATBR(Monoid) ATBR(SemiRing) ATBR(KleeneAlgebra) ATBR(Model_RegExp) Coq(Bool)