generate prime list with sieve and unfoldr

prime.hs

import System.Environment
import Data.List

prime :: [Int]
prime = unfoldr (\(x:xs) -> Just (x, sieve x xs)) [2..]

prime' :: Int ->  [Int]
prime' limit = unfoldr con [2..limit] where
      con [] = Nothing
      con (x:xs) = Just (x, sieve x xs)


sieve :: Int -> [Int] -> [Int]
sieve n xs = filter (\x -> (x `mod` n) > 0) xs

main = do
  [limit] <- map read `fmap` getArgs
  putStr $ show $ takeWhile (< limit) prime