anchor.diff:  safe_div(A, B) -> A / B.
   
   
  +-spec sort_non_null(variadic_metrics()) -> {variadic_metrics(), integer()}.
   sort_non_null(Values) ->
       sort_non_null(Values, [], 0).
   
  
positive.code:     safe_pow(Vs, math:pow(Current, Val)).
  
  
  safe_min(Vs) ->
      safe_min(Vs, null).
  
  
negative.code:          safe_square_root/1]).
  
  
  -type variadic_metric() :: metric_tuple() | metric_value().
  -type variadic_metrics() :: [variadic_metric()].
  
  
  -spec safe_average(variadic_metrics()) -> number().
  safe_average(Values) ->
      safe_average(Values, 1, 0.0).
  
  