Data update

Task/Knuth-shuffle/Standard-ML/knuth-shuffle.ml

@@ -0,0 +1,23 @@
+val rng = ref (SplitMix64.init NONE)
+
+fun getRandInt max =
+  let
+    val (rng', next) = SplitMix64.nextRange (0, max)
+    val () = rng := rng'
+  in
+    Word64.toInt next
+  end
+
+fun knuthShuffle a =
+  let
+    val i = ref ((Array.length a) - 1)
+  in
+    while !i > 0 do
+      let
+        val a_i = Array.sub (a, !i)
+        val j = getRandInt !i
+        val a_j = Array.sub (a, j)
+      in
+        (Array.update (a, !i, a_j); Array.update (a, j, a_i); i := (!i - 1))
+      end
+  end