anchor.diff:  
   %%--------------------------------------------------------------------
   %% @doc
  -%% 
  +%%
   %% @end
   %%--------------------------------------------------------------------
   -spec write(mfile(), pos_integer(), binary(), non_neg_integer(), binary()) ->
  
positive.code: 
  %%--------------------------------------------------------------------
  %% @doc
  %% 
  %% @end
  %%--------------------------------------------------------------------
  -spec fold(file:filename_all() | mfile(), pos_integer(), fold_fun(), pos_integer(), term()) -> term().
  
negative.code:     set_bitmap(R, I+1, B1).
  
  get_bitmap(Pos, M = #mfile{bitmaps = BMPs}) ->
      case maps:find(Pos, BMPs) of
          {ok, B} ->
              {B, M};
          error ->
  