tasks a-s

Task/Run-length-encoding/Oz/run-length-encoding.oz

@@ -0,0 +1,37 @@
+declare
+  fun {RLEncode Xs}
+     for G in {Group Xs} collect:C do
+	{C {Length G}#G.1}
+     end
+  end
+
+  fun {RLDecode Xs}
+     for C#Y in Xs append:Ap do
+	{Ap {Replicate Y C}}
+     end
+  end
+
+  %% Helpers
+  %% e.g. "1122" -> ["11" "22"]
+  fun {Group Xs}
+     case Xs of nil then nil
+     [] X|Xr then
+	Ys Zs
+        {List.takeDropWhile Xr fun {$ W} W==X end ?Ys ?Zs}
+     in
+        (X|Ys) | {Group Zs}
+     end
+  end
+  %% e.g. 3,4 -> [3 3 3 3]
+  fun {Replicate X N}
+     case N of 0 then nil
+     else X|{Replicate X N-1}
+     end
+  end
+
+  Data = "WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW"
+  Enc = {RLEncode Data}
+in
+  {System.showInfo Data}
+  {Show Enc}
+  {System.showInfo {RLDecode Enc}}