simple toy example of shuffling numbers around

examples/shuffling.rkt

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+#lang planet dyoo/whalesong
+
+
+
+;; shuffle: vector -> vector
+;; Reorders the contents of a vector according to the Fisher-Yates shuffling algorithm.
+(define (shuffle! a-vec)
+  (letrec ([iter (lambda (i)
+                   (cond
+                    [(<= i 0)
+                     a-vec]
+                    [else
+                     (let* ([index (random (add1 i))]
+                            [t (vector-ref a-vec i)])                       
+                       (vector-set! a-vec i (vector-ref a-vec index))
+                       (vector-set! a-vec index t)
+                       (iter (sub1 i)))]))])
+    (iter (sub1 (vector-length a-vec)))))
+ 
+(shuffle! (vector))
+(shuffle! (vector 'one))
+(shuffle! (vector 1 2))
+(shuffle! (vector "red" "white" "blue"))
+(shuffle! (list->vector (string->list "abcdefghijklmnopqrstuvwxyz")))