Number classification in Haskell

Classifier.hs

data Classification = Perfect | Abundant | Deficient deriving (Eq, Show, Ord)

squareRoot :: Int -> Int
squareRoot = floor . sqrt . fromIntegral

isFactor :: Int -> Int -> Bool
isFactor a b = a `mod` b == 0

factors :: Int -> [Int]
factors n = lowFactors ++ highFactors
    where lowFactors = filter (isFactor n) [1..limit]
          limit = squareRoot n
          highFactors = map (n `div`) lowFactors

classify :: Int -> (Int, Classification)
classify n
    | sumOfFactors == n'  = (n, Perfect)
    | sumOfFactors < n'   = (n, Deficient)
    | sumOfFactors > n'   = (n, Abundant)
    where n' = 2 * n
          sumOfFactors = sum $ factors  n

perfectNumbers = filter (\(n, c) -> c == Perfect) $ map classify [1..]

Do you have a link to the talk? I'd be interested.

http://www.infoq.com/presentations/Functional-Thinking