anchor.diff:     | title
      | include
      | rw
  +   | rb
  +   | rs
      ;
   
   rw
      : name? RW expression
  +   ;
  +
  +rb
  +   : name? RB expression
  +   ;
  +
  +rs
  +   : name? RS expression
      ;
   
   cseg
  
positive.code:    | ptr expression
     | NOT expression
     | OFFSET expression
     ;
  
  ptr
  
negative.code:    ;
  
  
  RB
     : R B
     ;
  
  
  RS
     : R S
     ;
  
  
  LENGTH
     : L E N G T H
     ;
  
  
  COMMENT
     : ';' ~ [\r\n]*
     ;
  