anchor.diff:    ;
   
   row_list :
  -     (row) (row_separator+ row)*
  +     row (row_separator+ row)*
     ;
   
   row :
  -     element_list (element_separator+)?
  +     element_list element_separator*
     ;
   
   row_separator :
  
positive.code:   ;
  
  element_list :
       (element) (element_separator+ element)*
    ;
    
  element :
  
negative.code:   |  COLON
    ;
  
  literal :
       NUMBER
    |  STRING
  