Data commit

Task/Ackermann-function/Haskell/ackermann-function-1.hs

@@ -0,0 +1,7 @@
+ack :: Int -> Int -> Int
+ack 0 n = succ n
+ack m 0 = ack (pred m) 1
+ack m n = ack (pred m) (ack m (pred n))
+
+main :: IO ()
+main = mapM_ print $ uncurry ack <$> [(0, 0), (3, 4)]

Task/Ackermann-function/Haskell/ackermann-function-2.hs

@@ -0,0 +1,10 @@
+import Data.List (mapAccumL)
+
+-- everything here are [Int] or [[Int]], which would overflow
+-- * had it not overrun the stack first *
+ackermann = iterate ack [1..] where
+	ack a = s where
+		s = snd $ mapAccumL f (tail a) (1 : zipWith (-) s (1:s))
+	f a b = (aa, head aa) where aa = drop b a
+
+main = mapM_ print $ map (\n -> take (6 - n) $ ackermann !! n) [0..5]