primes-no-div.hs

module Main where

import Data.Functor.Foldable
import Data.Maybe

g :: (Ord a, Num a) => (a, [[a]]) -> Prim [Maybe a] (a, [[a]])
g (n, xs)
  | n `elem` concatMap (take 1) xs'
    = Cons Nothing (n + 2, xs')
  | otherwise
    = Cons (Just n) (n + 2, iterate (+ (2 * n)) (n * n) : xs')
  where xs' = map (dropWhile (< n)) xs

primes :: [Int]
primes = 2 : catMaybes (ana g (3, []))