方案：R5RS:: 使其成为万位值

Question

(define m (expt 2 32))
(define a 22695477)
(define c 1.0)

(define (integers-starting-from n)
    (stream-cons n (integers-starting-from (+ n 1))))

(define (prng seed)
  (define xn (remainder (+ c (* a seed)) m))
  (define prn (/ (remainder (+ c (* a seed)) m) m))
  (stream-cons prn
               (prng xn)))

当我运行这段代码时，我当前的输出是

(stream->list (prng 3) 5)
> (0.015852607786655426 0.4954120593611151 0.998752823099494 0.7253396362066269 0.03071586787700653)

但输出必须是

(stream->list (prng 3) 5)
> (0.01585 0.4954 0.9988 0.7253 0.0307)

如何输出到万位值？

Answer 1

这是一种方法，如果您使用的是 Racket：

(define (prng seed)
  (define xn (remainder (+ c (* a seed)) m))
  (define prn (/ (remainder (+ c (* a seed)) m) m))
  (stream-cons (truncate prn 4)
               (prng xn)))

(define (truncate num precision)
  (string->number (~r num #:precision precision)))

现在输出将是：

'(0.0159 0.4954 0.9988 0.7253 0.0307)