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  1. isPerfect :: (Integral a) => a -> Bool
  2. isPerfect n = result
  3.   where limit  = ceiling (sqrt (fromIntegral n))
  4.         result = case filter (\k -> n`mod`k == 0) [2..limit] of
  5.           (d1:d2:_) -> n == d1*d2
  6.           [d1]      -> n`div`d1 /= d1
  7.           _         -> False
  8.  
  9. main = print (length (takeWhile (<=1000000) perfects))
  10.   where perfects = filter isPerfect [6..] :: [Int]
  11.  
Success #stdin #stdout 5.4s 6264KB
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https://ideone.com/htJGkZ
language:
Haskell (ghc 8.4.4)
created:
11 years ago
visibility:
secret

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