[Haskell-cafe] Re: How do I avoid stack overflows?
DavidA
polyomino at f2s.com
Sat Mar 17 04:01:49 EDT 2007
Hi,
Thanks for the suggestions. A few more questions.
The (<<*>>) function is just one of a number of lazy matrix arithmetic
functions that I have. If I need them to be evaluated strictly, is it best to
modify the matrix code, or the code that's calling it?
In this case, it looks like I can fix the problem by modifying the calling
code. For example:
test3 = iterate' (\m -> sum (map last m) `seq` m <<*>> id3) id3 !! 1000000
This works fine with the *unmodified* version of (<<*>>). However, note that
I've had to do some unnecessary work - sum (map last m). Is there a better way?
Or, is it better to modify the matrix code itself? Perhaps there's an argument
that matrix arithmetic should be strict - after all, integer arithmetic is
strict. But it seems potentially useful to have at least (<<+>>) as lazy, so
that I can add together infinite matrices.
Which is best?
Thanks in advance.
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