すごいHaskell読書会 #15 - 練習問題復習 @ #1

goodnumber.hs

scanDigits :: Int -> Int -> (String, String)
scanDigits a x = (take a $ show x, drop a $ show x)

calcTuple :: (String, String) -> Int  
calcTuple (x, y) = (read x) + (read y)

calc :: Int -> (Int, Int)
calc x = (calcTuple (scanDigits 1 x), calcTuple (scanDigits 2 x))

checkCalc :: Int -> (Int, Int) -> Bool
checkCalc x (y, z) = ((x `mod` y) == 0) && ((x `mod` z) == 0)

check :: Int -> Bool 
check x = checkCalc x $ calc x

main = do 
    print $ take 4 $ filter (\x -> (x `mod` 10) /= 0) $ filter check [100..999]