Bergervei/Zufallszahlen

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<language>Scheme</language>
== Zufallszahlen und -listen ==

<code id="4d4e5cf0ab781" hidden>
;-- M. Hielscher / Chr. Wagenknecht / V. Berger --
(define random-maker
  (let* ((multiplier 48271)
         (modulus 2147483647)
         (apply-congruence
          (lambda (current-seed)
            (let ((candidate (modulo (* current-seed multiplier) modulus)))
              (if (zero? candidate)
                  modulus
                  candidate))))
         (coerce
          (lambda (proposed-seed)
            (if (integer? proposed-seed)
                (- modulus (modulo proposed-seed modulus)) 19880214))))
  (lambda (initial-seed)
    (let ((seed (coerce initial-seed)))
      (lambda args
        (cond ((null? args)
               (set! seed (apply-congruence seed))
               (/ (- modulus seed) modulus))
              ((null? (cdr args))
               (let* ((proposed-top
                       (ceiling (abs (car args))))
                      (exact-top
                       (if (inexact? proposed-top)
                           (inexact->exact proposed-top)
                           proposed-top))
                      (top
                       (if (zero? exact-top)
                           1
                           exact-top)))
                 (set! seed (apply-congruence seed))
                 (inexact->exact (floor (* top (/ seed modulus))))))
              ((eq? (cadr args) 'reset)
               (set! seed (coerce (car args))))
              (else
               (display "random: unrecognized message")
               (newline))))))))

(require-library 'sisc/libs/srfi/srfi-19)
(import srfi-19)

(define random (random-maker (time-nanosecond (current-time))))
</code>

<code id="4d4dd7fc25664">
;(define RandomSeed 123456789)

(define zufallszahl
  (lambda (max)
    (+ 1 (randomint max))))

(define zufallsliste
  (lambda (max anz)
    (if (= anz 0)
        ()
        (cons (zufallszahl max) (zufallsliste max (- anz 1))))))
</code>

<run id="4d4dd7fc256c8">
(zufallsliste 100 20)
</run>