Filtering an infinite list in Haskell

Question

I have the following code that implements the Sieve of Eratosthenes:

primes :: [Int]
primes = primes\' [2..]

primes\' :: [Int] -> [Int]
primes\' [] = []
         


        

Answer 1

In cases like this where you know that once the predicate returns false for an element, it won't ever return true for a later element, you can replace filter with takeWhile, which stops taking elements as soon as the predicate returns false for the first time.