yihuang/sum.hs

Created August 25, 2012 03:33

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sum

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sum.hs

	sum' :: Int -> Int
	sum' n = loop n 0
	where
	loop 0 x = x
	loop n x = loop (n-1) (x+n)

	main = print $ sum' 1000000000

metalman commented Aug 25, 2012

大哥，这个把几G的内存耗光了等了很久也没结果……
这个如何：

foldl' f z [] = z
foldl' f z (x:xs) = let z' = f z x in z' `seq` foldl' f z' xs

newsum = foldl' (+) 0

main = print $ newsum [1..100000000]

参照：
http://www.iteye.com/topic/366101

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