1000個の素数をファイルにカンマ区切りで各行10個ずつ出力するプログラム

prime.hs

isPrimeNumber :: Int -> [Int] -> Bool
isPrimeNumber n = not . any ((== 0) . (mod n)) . filter (<= sr)
  where
    sr = floor $ sqrt $ fromInteger $ toInteger n

createPrimeList :: Int -> [Int]
createPrimeList 0   = []
createPrimeList len = _create 3 [2]
  where
    _create n ps
      | len <= length ps   = reverse ps
      | isPrimeNumber n ps = _create (n + 2) (n : ps)
      | otherwise          = _create (n + 2) ps

mkString :: (Show a) => String -> [a] -> String
mkString _ [] = []
mkString d (x:[]) = (show x)
mkString d (x:xs) = (show x) ++ d ++ (mkString d xs)

make10 :: (Show a) => [a] -> [String]
make10 = _make . splitAt 10
  where
    _make (take10, [])   = (mkString "," take10) : []
    _make (take10, tail) = (mkString "," take10) : make10 tail

main :: IO()
-- main = putStrLn $ unlines $ make10 $ createPrimeList 1000
main = writeFile "prime.txt" $ unlines $ make10 $ createPrimeList 1000