anchor.diff:    |  cell_array
     |  access
     |  t_AT t_FILLER? name
  +  |  t_END //really only applies in args, but let Natlab handle that
     ;
   
   access :
  
positive.code:   ;
  
  arg_list :  
       (arg) (t_FILLER? t_COMMA t_FILLER? arg)*
    ;
    
  arg :
       expr
    |  t_COLON
    ;
  
  literal :
  
negative.code:   ;
  
  colon_expr :
       plus_expr  ;
    
  plus_expr :
       binary_expr
    ;
  
  binary_expr :
  