Re: [Haskell-beginners] list splitting - nice implementation?

For efficiency considerations, look at the "core" code generated. On Sun, Nov 18, 2012 at 2:06 AM, Emmanuel Touzery wrote:

That is EXACTLY the kind of answer i was hoping for! Great implementation, I'll be sure to reuse that trick of zipping with the tail of the list.. really really good.

I'm relieved it's not trivial (for me) to write since i could not come up with it, and happy i understand it :-)

Intuitively it's more expensive than what an imperative language would do (new list creations, going several times over the list -zip, spam, map - still O(n) though).

See first remark.

If it was in your project you'd use that, or would you use a more "straightforward" implementation and you came up with this one just because i asked explicitely for such a way?

On 18 Nov 2012 10:47, "Tobias Brandt" wrote:

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Here is a possible solution:

import Data.List

split xs = getSnds $ span (uncurry (<)) $ zip xs (tail xs) where getSnds (as, bs) = (map snd as, map snd bs)

firstPart xs = fst $ split xs

sndPart xs = snd $ split xs

This is a one pass algorithm, it works for infinite lists.

On 18 November 2012 08:45, Emmanuel Touzery wrote:

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-- -- Regards, KC