练习1.8
(define (good-enough? old new)
(and (< (/ old new) 1.001) (> (/ old new) 0.999)))
(define (improve guess x)
(/ (+ (/ x (* guess guess)) (* 2 guess)) 3))
(define (cube-root guess x)
(if (good-enough? guess (improve guess x))
guess
(cube-root (improve guess x) x)))
(define (cuberoot x) (cube-root 1.0 x))
练习1.30
(define (sum a b term next)
(define (iter a result)
(if (> a b)
result
(iter (next a) (+ result (term a)))))
(iter a 0))
测试
> (sum 1 5 (lambda (x) x) (lambda (x) (+ x 1)))
15
> (sum 1.0 5.0 (lambda (x) (/ 1 x)) (lambda (x) (+ x 1)))
2.283333333333333
注意
(lambda (x) (x)) 错误写法
(lambda (x) x) 正确写法
练习1.34
理论上,(f f) 等价于 (f 2)等价于(2 2) 应该会报过程未定义的错
可见二者的报错是相同的