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