On 7/12/20 11:52 AM, John Cowan wrote:
> Still trying to understand what Brad wants.

What I want is

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;;; Carefully step through the independent substreams of the i'th
;;; stream of random numbers.

(define (random-source-generator i)
   (let ((j 0))
     (lambda ()
       (let ((new-source (make-random-source))) ;; deterministic
         (random-source-pseudo-randomize! new-source i j)
         (set! j (+ j 1))
         new-source))))

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The following definitions from Arvydas's fork of SRFI 194 are OK with me:

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;;
;; Parameters & syntax
;;
(define current-random-source (make-parameter default-random-source))

(define-syntax with-random-source
   (syntax-rules ()
     ((_ random-source proc arg ...)
      (begin
        (unless (random-source? random-source)
          (error "expected random source"))
        (parameterize ((current-random-source random-source))
                      (proc arg ...))))))

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