anchor.diff:  unary_expr -> unary_op unary_expr :
   #unary_op{
     line=?line('$1'),
  -  type=op('$1'),
  +  type=?op('$1'),
     val='$2'
   }.
   unary_expr -> call_expr : '$1'.
  
positive.code:       end;
      {error, {Line, _, {Message, Token}}, _} ->
        {error, {Line, lists:flatten(io_lib:format("~p ~p", [Message, Token]))}}
    end.
  
  %% Extract operators from op tokens
  op({Op, _Line}) ->
    Op.
negative.code: -export([string/1]).
  -include("reia_nodes.hrl").
  -define(line(Node), element(2, Node)).
  -define(op(Node), element(1, Node)).
  -define(identifier_name(Id), element(3, Id)).
  
  %% Parse a given string with nicely formatted errors
  