langs a-z

Task/Knuth-shuffle/REBOL/knuth-shuffle.rebol

@@ -0,0 +1,18 @@
+REBOL [
+    Title: "Fisher-Yates"
+    Purpose: {Fisher-Yates shuffling algorithm}
+]
+
+fisher-yates: func [b [block!] /local n i j k] [
+    n: length? b: copy b
+    i: n
+    while [i > 1] [
+        if i <> j: random i [
+            error? set/any 'k pick b j
+            change/only at b j pick b i
+            change/only at b i get/any 'k
+        ]
+        i: i - 1
+    ]
+    b
+]