anchor.diff:  add_guards([Elem|Path], Guards, Cnt) ->
      add_guards(Path, [guard(Elem, Cnt) | Guards], Cnt+1).
   
  -guard(Elem, Cnt) when is_atom(Elem), Cnt > 0 ->
  +guard(Elem, Cnt) when Cnt > 0 ->
       {'==', {element, Cnt, '$1'}, Elem}.
   
   -spec size_guard(pos_integer()) -> tuple().
  
positive.code: 
  %% BAD uses internl knowledge of folsom metrics record
  %% This is a callback function used by
  %% riak_core_stat_calc_proc when it calculates a stats
  %% current value.
  calc_stat({Name, {metric, _Tags, gauge, _HistLen}}) ->
      GuageVal = folsom_metrics:get_metric_value(Name),
  
negative.code: %% some crazy people put funs in folsom gauges
  %% so that they can have a consistent interface
  %% to access stats from disperate sources
  calc_guage({function, Mod, Fun}) ->
      Mod:Fun();
  calc_guage(Val) ->
      Val.
  