[Haskell-cafe] GHC predictability

Andrew Coppin andrewcoppin at btinternet.com
Wed May 14 14:25:47 EDT 2008

Brandon S. Allbery KF8NH wrote:
> On 2008 May 13, at 17:01, Andrew Coppin wrote:
>> That definition of mean is wrong because it traverses the list twice. 
>> (Curiosity: would traversing it twice in parallel work any better?) 
>> As for the folds - I always *always* mix up
> It might work "better" but you're still wasting a core that could be 
> put to better use doing something more sensible.  It's pretty much 
> always best to do all the calculations that require traversing a given 
> list in a single traversal.

Yeah, you're probably right there. I mean, with sufficient inlining, 
maybe you would end up with a loop that doesn't even construct any 
heap-allocated list nodes, just adds up the integers as fast as it can 
generate them.

On the other hand, N(N+1)/2N is probably even faster! ;-) So I guess 
it's kinda of a daft example...

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