本章主要内容在于将基础计算的过程抽象出来成为一个普遍流程，以此增加函数应用的普遍性，提高后续使用时的上限。
练习1.29 辛普森积分
辛普森积分的数学性比较强，重点在于抽象积分过程，对积分系数进行分类讨论。
(define (even? x)( = (remainder x 2) 0))
(define (cube x)( * x x x))
(define (sum term a next b)(if ( > a b)0(+ (term a)(sum term (next a) next b))))
(define (simpsons f a b n)(define h ( / (- b a) n))(define (y k) (f (+ a (* k h))))(define (factor k)(cond ((or (= k 0) ( = k n)) 1) ((even? k) 2)(else 4)))(define (term k) (* (factor k)(y k)))(define (next k) (+ k 1))(* ( / h 3) (sum term next n))
)1.30 将抽象中的递归过程改写为迭代过程，练手题。
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(define (sum term a next b)(define (iter a result)(if ( > a b)result(iter (next a) ( + (term a) result))))(iter a 0))
1.31 对pi值的乘法展开过程的抽象
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(define (even? x)(= (remainder x 2.0) 0))
(define (next x) (+ x 2))
(define (f a b k n)(cond ((> k n) 1.0)((even? k) (* (/ a b) ( f (next a) b (+ k 1) n)))(else (* (/ a b) ( f a (next b) (+ k 1) n)))))
(define (f 2 3 0 100))
同1.30 将乘法过程做一个迭代的改写
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(define (product term a next b)(define (iter a result))(if ( > a b)result(iter (next a) (* (term a) result)))(iter a 1))
1.32 引入combiner和null-value，将乘法和加法过程统一抽象为一个过程。
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(define (accmulate combiner null-value term a next b)(if (> a b)null-value(combiner (term a)(accumulate combiner null-value (next a) next b))))
1.33中的一个实例，通过accmulate的过程结合一定的筛选方式（如prime筛选素数）进行特定范围的计算。
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(define (prime? n)( = n (smallest-divisor n)))
(define (smallest-divisor n)( find-divisor n 2))
(define (find-divisor n test-divisor)(cond ((> (* test-divisor test-divisor) (* n n)) n)((divisor? test-divisor n) test-divisor)(else (find-divisor n (+ test-divisor 1)))))
(define (divisor? a b)( = (remainder b a) 0))
(define (ori a) a)
(define (next a) (+ a 1))
(define (filtered-accmulate prime? combine null-value term a next b)(cond ((> a b) null-value)((prime? a) (combine (term a) (filtered-accmulate prime? combine null-value term (next a) next b)))(else (filtered-accmulate prime? combine null-value term (next a) next b))))
(define (prime-sum a b)(filtered-accmulate prime? + 0 ori a next b))