list comprehension - Haskell Does Not Evaluate Lazily takeWhile -

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isqrt :: integer -> integer isqrt = floor . sqrt . fromintegral  primes :: [integer] primes = sieve [2..]  sieve (p:ps) = p : sieve [x | x <- ps, x `mod` p > 0]  primefactors :: integer -> [integer] primefactors n = takewhile (< n) [x | x <- primes, n `mod` x == 0]

here code. think guessed trying do: list of prime factors of given number using infinite list of prime numbers. code not evaluate lazily.

when use ghci , :l mycode.hs , enter primefactors 24, result [2, 3 ( , cursor flashing there) there isn't further prelude> prompt. think there problem there. doing wrong?

thanks.

takewhile never terminates composite arguments. if n composite, has no prime factors >= n, takewhile sit there.

apply takewhile primes list , filter result n mod x, this:

primefactors n = [x | x <- takewhile (<= n) primes, n `mod` x == 0]

(<= used instead of < maximum correctness, prime factors of prime number consist of number).


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