anchor.diff:                     true             -> ok end,
                   {Proj2, tango:add_back_pointer(StreamNum, BackPs, LPN)}
           end,
  -    {_Px, BackPs} = Res = lists:foldl(F, {Proj0, InitialBackPs}, Pages),
  -    io:format(user, "BackPs ~w\n", [BackPs]),
  +    {_Px, _BackPs} = Res = lists:foldl(F, {Proj0, InitialBackPs}, Pages),
  +    %% io:format(user, "BackPs ~w\n", [_BackPs]),
       Res.
   
   scan_backward_test() ->
  
positive.code:     BackPs0 = [{StreamNum, []}],
      {P2, BackPs1} = write_stream_pages(P1, Pages, PageSize, BackPs0, StreamNum),
      LastLPN = hd(proplists:get_value(StreamNum, BackPs1)),
      io:format(user, "\nLastLPN ~p\n", [LastLPN]),
  
      LastLPN=LastLPN,
      [begin
  
negative.code:          %% oldest -> newest (i.e. smallest LPN to largest LPN) order
           %% together with the actual page data.
           ShouldBePages = tango:scan_backward(P2, StreamNum, BackwardStartLPN,
                                               true),
           ok
       end || BackwardStartLPN <- lists:seq(1, NumPages)],
  
      ok.
  