guile-risk-calculator/random.scm

(define-module (random))


(use-modules
 ;; SRFI-27 for random number utilities
 (srfi srfi-27))


(define-public make-random-integer-generator
  (lambda* (#:key seed)
    "Get a procedure for generating uniformly distributed
random integers from 0 up to a not included bound, which is
seeded by the keyword argument seed, which must be a
positive integer."
    (cond
     [seed
      (let ([rand-src (make-random-source)])
        ;; Set the given seed to guarantee same results for
        ;; same invokations.
        (random-source-pseudo-randomize! rand-src 0 seed)
        ;; Obtain a procedure, which gives uniformly
        ;; distributed integers.
        (random-source-make-integers rand-src))]
     [else
      (let ([rand-src (make-random-source)])
        ;; Try to make the random source truly random. How
        ;; this works depends on the specific implementation
        ;; of SRFI-27.
        (random-source-randomize! rand-src)
        (random-source-make-integers rand-src))])))