Ltac select_left n :=
  repeat match goal with
 | |- context [(_ * mark ?i _ * mark n _)] =>
      rewrite (swap_mark1 i n); [ | solve [simpl; auto]]
 | |- context [(mark ?i _ * mark n _)] =>
      rewrite (swap_mark0 i n); [ | solve [simpl; auto]]
end.Ltac select_all n := match n with
                                | O => idtac
                                | S ?n' => select_left n; select_all n'
                              end.Ltac markem n P :=
   match P with
   | (?Y * ?Z) =>
        (match goal with H: mark _ Z = Z |- _ => idtac end
        || assert (mark n Z = Z) by auto); markem (S n) Y
   | ?Z =>  match goal with H: mark _ Z = Z |- _ => idtac end
                || assert (mark n Z = Z) by auto
  end.Ltac prove_assoc_commut :=
 clear;
 try (match goal with |- ?F _ -> ?G _ => replace G with F; auto end);
  (repeat rewrite <- sepcon_assoc;
   match goal with |- ?P = _ => markem O P end;
   let LEFT := fresh "LEFT" in match goal with |- ?P = _ => set (LEFT := P) end;
  match goal with H: mark ?n _ = _ |- _ =>
     repeat  match goal with H: mark ?n _ = ?P |- _ => rewrite <- H; clear H end;
     select_all n;
     reflexivity
   end).

Lemma test_prove_assoc_commut {T}{NA: NatDed T}{SA: SepLog T} : forall A B C D E : T, D * E * A * C * B = A * B * C * D * E.