anchor.diff:      | (term (LT | GT | EQUALS) term)
       ;
   
  -comment
  -    : SEMICOLON ~(CR)*
  -    ;
  -
   identifier
       : IDENTIFIER
       ;
  
positive.code: subproc
      : identifier (LPAREN paramlist? RPAREN)? (SPACE* command)+
      ;
          
  command
      : set_
      | for_
  
negative.code:     ;
  
  write_
      : (WRITE) SPACE* arglist
      ;
  
  quit_
  