yanfeng42

;; 基于 https://cisco.github.io/ChezScheme/csug9.5/csug9_5.pdf 的 12.10. Times and Dates

(define (time-prime-test n)
    (newline)
    (display n)
    (start-prime-test n (current-time))
)

(define (start-prime-test n start-time)
    (if (prime? n)

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(define (miller-rabin-test n)
    (define (try-it a)
        ; 因为 1 小于n, 所以 a/n 的余数就是 1.
        (= (expmode a (- n 1) n) 1)
    )
    (try-it (+ 1 (random (- n 1))))
)

(define (expmod base exp m) 
   (define (squaremod-with-check x) 

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(define (sum term a next b)
    (if (> a b)
        0
        (+ (term a)
           (sum term (next a) next b)
        )
    )
)

; 结果逼近 Π/8

yanfeng42

(define (sum term a next b)
    (if (> a b)
        0
        (+ (term a)
           (sum term (next a) next b)
        )
    )
)

; 求立方.

yanfeng42

(define (product term a next b)
    (if (> a b)
        1
        (* (term a)
           (product term (next a) next b)
        )
    )
)

(define (product term a next b)

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(define (accumulate combiner null-value term a next b)
    (if (> a b)
        null-value
        (combiner (term a)
           (accumulate combiner null-value term (next a) next b)
        )
    )
)

(define (accumulate combiner null-value term a next b)

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(define (filtered-accumulate combiner null-value term a next b filter?)
    (if (> a b)
        null-value
         (combiner (if (filter? a) (term a) null-value)
                (filtered-accumulate combiner null-value term (next a) next b filter?)
            )
    )
)

(define (filtered-sum term a next b filter?)

yanfeng42

; 我的答案:
; 递归写法.
(define (cont-frac-full n d k calculator)
    (define (iterator i)
        (if (< i k)
            (/ (n i) (calculator (d i) (iterator (+ i 1))))
            (/ (n i) (d i))
        )
    )

yanfeng42

(define (newton-transform g)
    (lambda (x)
        (- x (/ (g x) ((deriv g) x)))))

(define (deriv g)
    (lambda (x)
        (/ (- (g (+ x dx)) (g x))
            dx)
    )
)   

yanfeng42

(define (png-size w h) (* w h 4.0 1/1024))