On Sat, Sep 30, 2006 at 04:36:02PM +0100, Neil Mitchell wrote:
(if you can't be bothered to do that, the answer is "lines" ;)
although this wasn't the original problem, i like it, too :). but now i am stuck in finding an optimal implementation for lines. the following implementation is slightly slower than the built-in function, and i suspect this to stem from the occurrance of reverse for each line: cut1 :: String -> [String] cut1 = f "" where f x "" = [reverse x] f x ('\n':xs) = reverse x : f "" xs f x (c:xs) = f (c:x) xs i vaguely remember having seen a CPS trick here before, but all i can come up with is the yet a little slower cut2 :: String -> [String] cut2 = f id where f k "" = [k ""] f k ('\n':xs) = k "" : f id xs f k (c:xs) = f k' xs where k' cs = k (c:cs) also, i think both implementations are line-strict, that is, each line is fully evaluated once touched in the first character. is there a similar implementation, with CPS or not, that is lazy in the lines and more efficient? thanks, matthias