28 lines
708 B
Racket
28 lines
708 B
Racket
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#! /usr/bin/racket
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#lang racket/base
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(define (product term a next b)
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(define (iter a result)
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(if (> a b)
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result
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(iter (next a) (* (term a) result))))
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(iter a 1))
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(define (numerator pre-applying n)
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(* pre-applying (product (lambda (x) (* x x)) 4 (lambda (x) (+ x 2)) n)))
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(define (denominator pre-applying n)
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(* pre-applying (product (lambda (x) (* x x)) 3 (lambda (x) (+ x 2)) n)))
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(define (fourth-of-pi n)
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(cond ((< n 1) 0)
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((even? n) (/ (numerator (* 2 (+ n 2)) n)
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(denominator 1 ( + n 1))))
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(else (/ (numerator 2 (+ n 1))
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(denominator (+ n 2) n)))))
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(fourth-of-pi 1)
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(fourth-of-pi 2)
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(fourth-of-pi 3)
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(fourth-of-pi 60)
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