[Haskell-cafe] Re: GHC predictability

Andrew Coppin andrewcoppin at btinternet.com
Wed May 14 14:29:02 EDT 2008

Richard A. O'Keefe wrote:
> On 14 May 2008, at 8:58 am, Andrew Coppin wrote:
>> What I'm trying to say [and saying very badly] is that Haskell is an 
>> almost terrifyingly subtle language.
> Name me a useful programming language that isn't.
> Simply interchanging two for-loops, from
>     for (i = 0; i < N; i++) for (j = 0; j < N; j++)
> to    for (j = 0; j < N; j++) for (i = 0; i < N; i++)
> when marching over an array, can easily slow you down
> by nearly two orders of magnitude in C.
> [Hint: read "What every computer scientist needs to know
> about memory".] 

OK, well *that* is news... :-o

I would suggest that for heap-allocated data that isn't an array, both 
cases will be equally unperformant. I can't prove that though...

> "Unexpectedly slow" is better than "inexplicably buggy".

+184   o_O

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