anchor.diff:  
   %% gen_server implementation.
   
  -init([]) -> {ok, dict:new()}.
  -terminate(_Reason, _Dict) -> ok.
  -code_change(_OldVsn, Dict, _Extra) -> {ok, Dict}.
  -handle_info(_Info, Dict) -> {noreply, Dict}.
  -handle_cast(_Msg, Dict) -> {noreply, Dict}.
  +init([]) -> {ok, #dmgr{curr = dict:new()}}.
  +terminate(_Reason, _DMgr) -> ok.
  +code_change(_OldVn, DMgr, _Extra) -> {ok, DMgr}.
  +handle_info(_Info, DMgr) -> {noreply, DMgr}.
  +handle_cast(_Msg, DMgr) -> {noreply, DMgr}.
   
  -handle_call({monitor, Addr}, _From, Dict) ->
  -    {Dict2, #mbox{pid = Pid}} = make_mbox(Dict, Addr),
  +handle_call({monitor, Addr}, _From, DMgr) ->
  +    {DMgr2, #mbox{pid = Pid}} = make_mbox(DMgr, Addr),
       Reply = {ok, erlang:monitor(process, Pid)},
  -    {reply, Reply, Dict2};
  +    {reply, Reply, DMgr2};
   handle_call({send, Addr, Op, NotifyPid,
  -             ResponseFun, CmdModule, Cmd, CmdArgs}, _From, Dict) ->
  -    {Dict2, #mbox{pid = Pid}} = make_mbox(Dict, Addr),
  +             ResponseFun, CmdModule, Cmd, CmdArgs}, _From, DMgr) ->
  +    {DMgr2, #mbox{pid = Pid}} = make_mbox(DMgr, Addr),
       Pid ! {Op, NotifyPid, ResponseFun, CmdModule, Cmd, CmdArgs},
  -    {reply, ok, Dict2}.
  +    {reply, ok, DMgr2}.
   
   % ---------------------------------------------------
   
   % Retrieves or creates an mbox for an Addr.
  -make_mbox(Dict, Addr) ->
  +make_mbox(#dmgr{curr = Dict} = DMgr, Addr) ->
       case dict:find(Addr, Dict) of
  -        {ok, MBox} -> {Dict, MBox};
  +        {ok, MBox} -> {DMgr, MBox};
           _ -> MBox = create_mbox(Addr),
                Dict2 = dict:store(Addr, MBox, Dict),
  -             {Dict2, MBox}
  +             {#dmgr{curr = Dict2}, MBox}
       end.
   
   create_mbox(Addr) ->
  
positive.code: -compile(export_all).
  
  -record(mbox, {addr, pid, history}).
  
  %% API for downstream manager service.
  
  
negative.code: %
  mbox_test() ->
      D1 = dict:new(),
      M1 = #dmgr{curr = D1},
      A1 = mc_addr:local(),
      {M2, B1} = make_mbox(M1, A1),
      ?assertMatch({M2, B1}, make_mbox(M2, A1)).
  
  