-- sieve.hs — lazy sieve of Eratosthenes.
--
-- Each recursive call to `sieve` consumes one prime `p` off the front
-- of the input stream and produces an infinite stream of composites
-- filtered out via `filter`. Because cons is lazy, only as much of
-- the stream is forced as demanded by `take`.

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

primes = sieve [2..]

result = take 10 primes