anchor.diff:     : '||'
      ;
   
  -
  -DELIM
  -   : 'delim'
  -   ;
  -
  -
   ASTROOT
      : 'astroot'
      ;
  
positive.code:    ;
  
  post_event
     : post_event_sub delim
     ;
  
  exit_statement_sub
  
negative.code:    ;
  
  assignment_statement
     : assignment_sub SEMI? 
     ;
  
  lvalue_sub
  