#lang racket
(require racket/trace)

(define cont #f)

(define fac
  (lambda (n)
    (if (eq? n 0)
        (call/cc (lambda (k) (set! cont k) 1))
        (* n (fac (- n 1))))))
(trace fac)

(define fac2
  (lambda (n)
    (if (eq? n 0)
        1
        (if (eq? n 3)
            (begin (call/cc (lambda (k) (set! cont k)))
                   (* n (fac2 (- n 1))))
            (* n (fac2 (- n 1)))))))
(trace fac2)

;;; (+ 3 (call/cc (lambda (k) (+ 12 (k 42) 88))) 101)