练习2.4 2.5

#lang racket
#|
;: 练习2.4
(define (cons x y)
(lambda (m) (m x y)))

(define (car z)
(z (lambda (p q) p)))

(define (cdr z)
(z (lambda (p q) q)))

(define z (cons 'a 'b))
z
(car z)
(cdr z)

|#

;: 练习 2.5
(define (cons a b)
(* (expt 2 a)
(expt 3 b)))
;:
(define (car z)
(if (= 0 (remainder z 2)) ;: 整除则+1
(+ 1 (car (/ z 2)))
0))
;:
(define (cdr z)
(if (= 0 (remainder z 3))
(+ 1 (cdr (/ z 3)))
0))
;: 测试
(define z (cons 9 8))
(car z)
(cdr z)