anchor.diff:     : P T R
      ;
   
  -
  -NOT
  -   : N O T
  -   ;
  -
  -
  -
  -
   REGISTER
      : 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
     : opcode? expressionlist?
     ;
  
  lbl
  
negative.code:    ;
  
  STRING2
     :  '\u0027' ~ ['\u0027']* '\u0027'
     ;
  
  
  