[Haskell-cafe] Re: GHC predictability

Richard A. O'Keefe ok at cs.otago.ac.nz
Wed May 14 01:35:16 EDT 2008

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".]  For a real shock, take a look at what
your C++ templates are doing...

There's one big difference between Haskell and language T (my other
preferred language).  Seemingly insignificant changes in Haskell can
kill performance, but seemingly insignificant changes in language T
can take you into territory the library designers never thought of
where there are lions, tigers, and bears in abundance.  "Unexpectedly
slow" is better than "inexplicably buggy".

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