(define-syntax if-not
  (syntax-rules ()
    ((_ c t f) (if (not c) t f))
    ((_ c t) (if (not c) t))))

(write (macroexpand-1 '(if-not #t 123 456)))

(define (main)
  (let loop ((datum (read)))
    (unless (eof-object? datum)
      ())))