Exercise 3.9 · 习题

Exercise 3.9: In 1.2.1 we used the
substitution model to analyze two procedures for computing factorials, a
recursive version

(define (factorial n)
(if (= n 1)
1
(* n (factorial (- n 1)))))

and an iterative version

(define (factorial n)
(fact-iter 1 1 n))

(define (fact-iter product
counter
max-count)
(if (> counter max-count)
product
(fact-iter (* counter product)
(+ counter 1)
max-count)))

Show the environment structures created by evaluating (factorial 6)

using each version of the factorial procedure.

练习 3.9：在 1.2.1 中，我们用代换模型分析了两个计算阶乘的过程，一个是递归版本

(define (factorial n)
(if (= n 1)
1
(* n (factorial (- n 1)))))

另一个是迭代版本

(define (factorial n)
(fact-iter 1 1 n))

(define (fact-iter product
counter
max-count)
(if (> counter max-count)
product
(fact-iter (* counter product)
(+ counter 1)
max-count)))

请画出用两个版本的 factorial 过程分别对 (factorial 6) 求值时所创建的环境结构。