Data commit

Task/Look-and-say-sequence/Oz/look-and-say-sequence.oz

@@ -0,0 +1,30 @@
+declare
+  %% e.g. "21" -> "1211"
+  fun {LookAndSayString S}
+     for DigitGroup in {Group S} append:Add do
+        {Add {Int.toString {Length DigitGroup}}}
+        {Add [DigitGroup.1]}
+     end
+  end
+
+  %% lazy sequence of integers starting with N
+  fun {LookAndSay N}
+     fun lazy {Loop S}
+        {String.toInt S}|{Loop {LookAndSayString S}}
+     end
+  in
+     {Loop {Int.toString N}}
+  end
+
+  %% like Haskell's "group"
+  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
+in
+  {ForAll {List.take {LookAndSay 1} 10} Show}