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16 lines
425 B
Haskell
16 lines
425 B
Haskell
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module Util.Primes where
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is_prime :: (Integral a) => a -> Bool
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is_prime n
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| n == 1 = False
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| n < 4 = True
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| n `rem` 2 == 0 = False
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| n < 9 = True
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| n `rem` 3 == 0 = False
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| otherwise = do
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let f = sqrt (fromIntegral n)
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let checkprime x = (n `rem` x == 0 || n `rem` (x + 2) == 0)
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not (or (map checkprime (takeWhile (<= floor f) [5,11..])))
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primes = filter is_prime (2:[3,5..])
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