On Wed, 19 Oct 2011 21:21:48 +0200, Gregory Collins
<g...@gregorycollins.net> wrote:
On Wed, Oct 19, 2011 at 5:03 PM, Johan Tibell <johan.tib...@gmail.com>
wrote:
It does. You need to use evaluate to have ensure actually be evaluated.
I'm almost certain you're wrong about this. The bang pattern on the
return from ensure (!r1 <- ensure $ ...) forces r1 to WHNF, which goes
through deepseq, and thus the whole list is forced. See
https://gist.github.com/1299380 for a short counterexample.
G
You don't need the ensure function or the bang patterns if you do it like
this:
main =
deepseq testList $
do
putStrLn "we survived without evaluating testList"
let x = foldl' (+) 0 $ take 50 testList
putStrLn $ "x was " ++ show x
Regards,
Henk-Jan van Tuyl
--
http://Van.Tuyl.eu/
http://members.chello.nl/hjgtuyl/tourdemonad.html
--
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