anchor.diff:     ;
   
   opcode
  -    : OPCODE
  -    | '[' OPCODE ']'
  -    ;
  +   : OPCODE
  +   ;
   
   comment
      : COMMENT
  
positive.code: grammar asm8086;
  
  prog
     : (line? EOL) +
     ;
  
  line
     : lbl? (instruction| directive)? comment?
     ;
  
  instruction
     : opcode expressionlist?
     ;
  
  directive
  
negative.code:    ;
  
  argument
     : number
     | DOLLAR
     | REGISTER
     | name
     | string
     | ('(' expression ')')
     | ('[' expression ']')
     | NOT expression
     | OFFSET expression
     ;
  
  string
     : STRING
  