#lang racket
(require racket/trace)

(define fac
  (lambda (n)
    (letrec ([foo (trace-lambda (n accu)
		    (if (zero? n)
			accu
			(foo (- n 1) (* n accu))))])
      (foo n 1))))

(define my-and
  (lambda (x y)
    (if x
        y
        #f)))

(define my-and-lambda
  (lambda (x y)
    (if (x)
        (y)
        #f)))