anchor.diff:      case ?ETS:lookup(DB, Key) of
           [{Key, {_Value, WriteLock, ReadLock, Version}}] ->
               {DB, {WriteLock, ReadLock, Version}};
  -        [] ->
  -            {DB, failed}
  +        [] -> {DB, failed}
       end.
   
   %% @doc reads the version and value of a key
  
positive.code:     case ?ETS:lookup(DB, Key) of
          [{Key, {_Value, _WriteLock, _ReadLock, Version}}] ->
              {ok, Version};
          [] ->
              failed
      end.
  
  %% @doc returns the number of stored keys
  
negative.code: %% @doc get keys and versions in a range
  get_range_with_version(DB, Interval) ->
      F = fun ({Key, {Value, WriteLock, ReadLock, Version}}, 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 Value =/= empty_val
                      andalso intervals:in(Key, Interval) of
                      true -> [{Key, Value, Version} | Data];
                      false -> Data
                  end
          end,
      ?ETS:foldl(F, [], DB).
  