29 Jan
2011
29 Jan
'11
9:16 a.m.
Hi everybody, after reading a post by Don Stewart on http://cgi.cse.unsw.edu.au/~dons/blog/2008/05/16#fast, I was not really satisfied with the necessity to rewrite mean xs = sum xs / fromIntegral (length xs) to an explicitly recursive function. I investigated a bit further and got really confused after the following GHCi session: Prelude> length [1..10^8] + length [1..10^8] 200000000 Prelude> let xs = [1..10^8] Prelude> length xs + length xs <interactive>: out of memory Can someone explain this and give a simple, reasonable rule by which I can predict such things in the future? Isn't it a pitfall? Tim