anchor.diff:  
   
   REGISTER
  -   : A X | B C | C X | D X | C I | D I | B P | S P | I P | C S | D S | E S | S S
  +   : A X | B X | C X | D X | C I | D I | B P | S P | I P | C S | D S | E S | S S
      ;
   
   
  
positive.code:    ;
  
  line
     : lbl? (assemblerdirective | instruction)? comment?
     ;
  
  instruction
  
negative.code: argument
     : number
     | DOLLAR
     | register
     | name
     | string
     | ('(' expression ')')
  