primes.hs

import System.Environment

isPrime :: Int -> Bool
isPrime a =
  let isOddBy x = a `mod` x /= 0
      gtSqr x = x * x <= a
  in  all isOddBy $ takeWhile gtSqr primes

primes :: [Int]
primes = 2 : filter isPrime [3..]

main = do
  args <- getArgs
  if length args == 0 then
    print "not enough arguments"
  else
    let count = read $ head args
    in print $ show $ take count primes