22 lines
694 B
Racket
22 lines
694 B
Racket
#lang racket/base
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(define (s-of-n-creator n)
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(define i 0)
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(define sample (make-vector n)) ; the sample of n items
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(lambda (item)
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(set! i (add1 i))
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(cond [(<= i n) ; we're not full, so kind of boring
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(vector-set! sample (sub1 i) item)]
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[(< (random i) n) ; we've already seen n items; swap one?
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(vector-set! sample (random n) item)])
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sample))
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(define counts (make-vector 10 0))
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(for ([i 100000])
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(define s-of-n (s-of-n-creator 3))
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(define sample (for/last ([digit 10]) (s-of-n digit)))
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(for ([d sample]) (vector-set! counts d (add1 (vector-ref counts d)))))
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(for ([d 10]) (printf "~a ~a\n" d (vector-ref counts d)))
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