anchor.diff:  
   meta(Line, Counter) -> [{counter,Counter}|meta(Line)].
   meta([Line, Column, EndColumn]) when is_integer(Line), is_integer(Column), is_integer(EndColumn) -> [{line, Line}];
  -meta(Line) when is_integer(Line) -> [{line, Line}];
   meta(Node) -> meta(?line(Node)).
   
   %% Operators
  
positive.code: Erlang code.
  
  -define(id(Node), element(1, Node)).
  -define(line(Node), hd(element(2, Node))).
  -define(exprs(Node), element(3, Node)).
  -define(rearrange_uop(Op), (Op == 'not' orelse Op == '!')).
  
  
negative.code: 
  %% Errors
  
  throw(Line, Error, Token) ->
    throw({error, {Line, ?MODULE, [Error, Token]}}).
  
  