poop wrote:

So I'm working my way thorough haskell, doing some programming problems, and I have this one so far:

Hi, I haven't spotted the problem in your code but there's an alternative solution to Euler Problem 14 on the wiki: http://www.haskell.org/haskellwiki/Euler_problems/11_to_20#Problem_14 -- it may be helpful as a comparison? Regards,

p14next n = if (mod n 2 == 0) then (div n 2) else (3*n + 1)

p14seqlen n = f' 1 n where f' accum n | n == 1 = accum | otherwise = f' (accum + 1) (p14next n)

sndmax a b = if snd a > snd b then a else b

p14 n = fst (f' (0,0) n) where f' maxTuple n | n == 0 = maxTuple | otherwise = f' (sndmax maxTuple (n, p14seqlen n)) (n-1)

the goal is to be able to run: p14 999999

and not get a stack overflow message. I read what was available on tail recursion and I think I have it working with tail recursion now, at least it gives me a stack overflow message really quickly compared to before :)

I have not been able to find any documentation on seq and ($!) which was also mentioned as a way to get rid of stack overflow messages so if those are what is required an explanation of those would be most helpful.

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