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September 2017 Update

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Ingy döt Net 2017-09-23 10:01:46 +02:00
parent bba7bfd280
commit ba8067c3b7
14570 changed files with 153136 additions and 63871 deletions
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28
Task/Perfect-numbers/Haskell/perfect-numbers-2.hs
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@ -1,15 +1,19 @@
perfect = map (\x -> (2^x - 1) * (2^(x - 1))) $
filter (\x -> isPrime x && isPrime (2^x - 1)) maybe_prime where
maybe_prime = scanl1 (+) (2:1:cycle [2,2,4,2,4,2,4,6])
isPrime n = all ((/=0).(n`mod`)) $
takeWhile (\x -> x*x <= n) maybe_prime
perfect =
(\x -> (2 ^ x - 1) * (2 ^ (x - 1))) <$>
filter (\x -> isPrime x && isPrime (2 ^ x - 1)) maybe_prime
where
maybe_prime = scanl1 (+) (2 : 1 : cycle [2, 2, 4, 2, 4, 2, 4, 6])
isPrime n = all ((/= 0) . (n `mod`)) $ takeWhile (\x -> x * x <= n) maybe_prime
isPerfect n = f n perfect where
f n (p:ps) = case compare n p of
EQ -> True
LT -> False
GT -> f n ps
isPerfect n = f n perfect
where
f n (p:ps) =
case compare n p of
EQ -> True
LT -> False
GT -> f n ps
main :: IO ()
main = do
mapM_ print $ take 10 perfect
mapM_ print $ map (\x -> (x, isPerfect x)) [6,27,28,29,496,8128,8129]
mapM_ print $ take 10 perfect
mapM_ (print . (\x -> (x, isPerfect x))) [6, 27, 28, 29, 496, 8128, 8129]