anchor.diff:  -export([ add/2
           , new/0
           , new/1
  +        , setopts/1
           ]).
   
   % DEBUG:
  
positive.code: char_in_ranges(C, [{_Min, _Max} | Rest]) -> char_in_ranges(C, Rest).
  
  %% order of magnitude for integers and floats
  mag(X) -> trunc(math:log10(abs(X))).
  
  
  %% Tests
  
negative.code: 
  %% Initialize, immediately adding one data term
  new(Data) -> add(Data, new()).
  
  
  %% Add an instance of Data to Spec.
  %% If Spec already contains Data, do nothing.
  