Scheme shuffle

Scheme

Public Domain

returns a list of numbers from one to n (inclusive) in a random order

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scheme shuffle 
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; shuffled: nat -> list
; returns a list of numbers from one to n (inclusive) in a
; random order
(define (shuffled n)
  (local
    [(define l (build-list n add1))
     (define (pull new old)
       (if (empty? old)
           new
           (local
             [(define rand (list-ref old (random (length old))))]
             (pull 
              (cons rand new)
              (filter (lambda (x) (not (= x rand))) old)))))]
    (pull empty (build-list n add1))))