2016-12-05 22:15:40 +01:00
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import Data.List (mapAccumL)
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2013-04-10 12:38:42 -07:00
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-- everything here are [Int] or [[Int]], which would overflow
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-- * had it not overrun the stack first *
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ackermann = iterate ack [1..] where
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ack a = s where
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2016-12-05 22:15:40 +01:00
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s = snd $ mapAccumL f (tail a) (1 : zipWith (-) s (1:s))
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f a b = (aa, head aa) where aa = drop b a
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2013-04-10 12:38:42 -07:00
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main = mapM_ print $ map (\n -> take (6 - n) $ ackermann !! n) [0..5]
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