module Example8 where

import Prelude hiding (take)

from n = n : from (n + 1)

take 0 _              = []
take n []     | n > 0 = []
take n (x:xs) | n > 0 = x : take (n-1) xs

sieve :: [Integer] -> [Integer]
sieve (x:xs) = x : sieve [x' | x' <- xs, x' `mod` x /= 0]

primes :: [Integer]
primes = sieve (from 2)

first20Primes = take 20 primes

prime500 = primes !! 500