anchor.diff:  avg([], Sum, Count)      -> float(Sum) / float(Count);
   avg([H | R], Sum, Count) -> avg(R, Sum + H, Count + 1).
   
  +float_round(X) -> float(trunc(1000.0 * X)) / 1000.0.
  +
   -ifdef(EUNIT).
   
   test() ->
  
positive.code:     ?assertEqual(0.0, avg([])),
      ?assertEqual(5.0, avg([5])),
      ?assertEqual(5.0, avg([5, 5, 5])),
      ?assertEqual(5.0, avg([1, 5, 10])),
      ok.
  
  -endif.
  
  
negative.code:     Samples6 = [{hit_ratio,
                   lists:zipwith(fun(undefined, _) -> 0;
                                    (_, undefined) -> 0;
                                    (Hits, Gets)   -> float_round(Hits / Gets)
                                 end,
                                 proplists:get_value("get_hits", Samples5),
                                 proplists:get_value("cmd_get", Samples5))} |
  