On Wed, Oct 19, 2011 at 12:21 PM, 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. I should have paid more attention; I missed the bangs on the bindings. I still recommend the pattern I linked in my previous email. If you want to do it they way you currently do use let !foo = xs `deepseq` xs no return needed.
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