21 lines
838 B
Racket
21 lines
838 B
Racket
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#lang racket
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(define (feigenbaum #:max-it (max-it 13) #:max-it-j (max-it-j 10))
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(displayln " i d" (current-error-port))
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(define-values (_a _a1 d)
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(for/fold ((a 1) (a1 0) (d 3.2))
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((i (in-range 2 (add1 max-it))))
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(let* ((a′ (for/fold ((a (+ a (/ (- a a1) d))))
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((j (in-range max-it-j)))
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(let-values (([x y] (for/fold ((x 0) (y 0))
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((k (expt 2 i)))
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(values (- a (* x x))
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(- 1 (* 2 y x))))))
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(- a (/ x y)))))
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(d′ (/ (- a a1) (- a′ a))))
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(eprintf "~a ~a\n" (~a i #:width 2) (real->decimal-string d′ 8))
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(values a′ a d′))))
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d)
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(module+ main
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(feigenbaum))
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