16 Feb
2011
16 Feb
'11
6:09 p.m.
On 16 February 2011 22:48, Daniel Fischer
The problem with that is that under certain circumstances the list is shared in nested loops, which was what caused the thread (it was mapM_ and not forM_, but I'd be very surprised if they behaved differently with -O2).
Yep - d'oh! Thinking about it some more, this example is actually quite interesting because if you *prevent* the list from being floated the forM gets foldr/build fused into a totally listless optimal loop. It really does seem like a shame to disable that optimisation because of the floating... if only the fusion hit before float-out was run. Max