This code was taken from the book "Haskell Road to Logic, Math and Programming". It implements sieve of eratosthenes algorithm and solves Project Euler Problem 10.
sieve :: [Integer] -> [Integer]
sieve (0 : xs) = sieve xs
sieve (n : xs) = n : sieve (mark xs 1 n)
where
mark :: [Integer] -> Integer -> Integer -> [Integer]
mark (y:ys) k m | k == m = 0 : (mark ys 1 m)
| otherwise = y : (mark ys (k+1) m)
primes :: [Integer]
primes = sieve [2..]
-- Project Euler #10
main = print $ sum $ takeWhile (< 2000000) primes
Actually it runs even slower then the naive prime test. Can someone explain this behaivour?
I suspect it has something to do with iterating each element in the list in the mark function.
Thanks.