17 lines
422 B
Haskell
17 lines
422 B
Haskell
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import Data.List (find)
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isqrt :: (Integral n) => n -> n
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isqrt = floor . sqrt . fromIntegral
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isPrime :: (Integral n) => n -> Bool
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isPrime n = (n >= 2) && all ((/= 0) . (n `mod`)) [2 .. isqrt n]
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goldbach :: (Integral n) => n -> (n, n)
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goldbach n =
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if odd n
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then error "Odd number was given"
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else (p, n - p)
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where
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Just p = find (\p -> (n - p) `elem` primes) primes
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primes = filter isPrime [2 .. n - 1]
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