(load "lab2x.ss")

(define reduce-count
  (lambda (exp continuation)
    ;applies continuation to answer and count
    (define loop
      (lambda (exp prior-reductions-count)
        (reduce-once-appl exp
                          (lambda (reduced-exp)
                            (loop reduced-exp
                                  (+ prior-reductions-count
                                     1)))
                          (lambda ()
                            (continuation exp 
                                  prior-reductions-count)))))
    (loop exp 0)))

(define repl
  (lambda ()
    (display "-> ")
    (let ((exp (parse (read))))
      (reduce-count 
       exp
       (lambda (answer count)
         (display "After ")
         (write count)
         (display " reductions, reached ")
         (write (unparse answer))
         (newline))))
    (repl)))