anchor.diff:  %% @doc get keys and versions in a range
   get_range_with_version(DB, Interval) ->
       F = fun ({Key, {Value, WriteLock, ReadLock, Version}}, Data) ->
  -                case intervals:in(Key, Interval) andalso Value =/= empty_val of
  -                    true ->
  -                        [{Key, Value, WriteLock, ReadLock, Version} | Data];
  -                    false ->
  -                        Data
  +                case  Value =/= empty_val
  +                    andalso intervals:in(Key, Interval) of
  +                    true -> [{Key, Value, WriteLock, ReadLock, Version} | Data];
  +                    false -> Data
                   end
           end,
       ?ETS:foldl(F, [], DB).
   
   get_range_only_with_version(DB, Interval) ->
       F = fun ({Key, {Value, WLock, _, Version}}, Data) ->
  -                case WLock == false andalso intervals:in(Key, Interval) andalso Value =/= empty_val of
  -                    true ->
  -                        [{Key, Value, Version} | Data];
  -                    false ->
  -                        Data
  +                case WLock == false
  +                    andalso Value =/= empty_val
  +                    andalso intervals:in(Key, Interval) of
  +                    true -> [{Key, Value, Version} | Data];
  +                    false -> Data
                   end
           end,
       ?ETS:foldl(F, [], DB).
  
positive.code: %%      sized groups
  get_middle_key(DB) ->
      case (Length = ?ETS:info(DB, size)) < 3 of
          true ->
              failed;
          false ->
              {ok, nth_key(DB, Length div 2 - 1)}
      end.
  
  nth_key(DB, N) ->
  
negative.code:                             ReadLock == 0 andalso
                              OldVersion < Version of
                              true ->
                                  ?ETS:insert(DB, {Key, {Value, WriteLock,
                                                         ReadLock, Version}}),
                                  DB;
                              false -> DB
                          end
                  end
          end,
  