30 lines
795 B
Plaintext
30 lines
795 B
Plaintext
(lib 'math) ;; Σ aka (sigma f(n) nfrom nto)
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(define (f-count N (times 100000))
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(define count 0)
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(for ((i times))
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;; new random f mapping from 0..N-1 to 0..N-1
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;; (f n) is NOT (random N)
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;; because each call (f n) must return the same value
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(define f (build-vector N (lambda(i) (random N))))
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(define hits (make-vector N))
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(define n 0)
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(while (zero? [hits n])
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(++ count)
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(vector+= hits n 1)
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(set! n [f n])))
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(// count times))
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(define (f-anal N)
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(Σ (lambda(i) (// (! N) (! (- N i)) (^ N i))) 1 N))
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(decimals 5)
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(define (f-print (maxN 21))
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(for ((N (in-range 1 maxN)))
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(define fc (f-count N))
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(define fa (f-anal N))
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(printf "%3d %10d %10d %10.2d %%" N fc fa (// (abs (- fa fc)) fc 0.01))))
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