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kcsongor/primes-no-div.hs

Created April 7, 2016 13:42
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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, []))
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