Lazy list still results in stack overflow

[erikd@…]

Simple Sieve of Eratosthenes :

primes = sieve $ rangeInfIntL 2

sieve (p : xs) =

p : sieve [ x | x <- xs, x mod p > 0 ]

main =

print $ show $ take 30 primes

when run results in:

*** DDC RTS PANIC! Slot stack overflow. Aborted (core dumped)

[benl]

If you create an infinite list you have to be careful not to demand it all at once.

For this one, suspend the application of sieve to the list, and generate the list comprehension in a lazy way (not the <@- operator)

primes = sieve $ rangeInfIntL 2

sieve (p : xs)
	= p : sieve @ [ x | x <@- xs, x `mod` p /= 0 ]

main () =
	print $ show $ take 30 primes