[Haskell-beginners] Re: [Haskell-begin] Maximum of a List?
Niels Aan de Brugh
nielsadb at gmail.com
Mon Jul 28 12:15:36 EDT 2008
Steve Klabnik wrote:
> I think you're onto something with the Int/Integer thing....when using
> a type signature of "Integer", "f 1 113383" gives "248" immediately.
> Compiling and running the code with "Integer" types on my home machine
> yields "525".... which Euler says isn't the right answer?
Because you're not providing the right number. :-)
> Also, on the strictness annotations: Do you put them in the type
> declaration? Or in the pattern match on the lhs of the declaration?
I've tested your code with strictness annotations and it appears to not
make a difference. GHC employs several optimization techniques, one of
those being strictness analysis, so maybe it is already using a strict,
The real speed-up (a non-linear one) here is not to re-calculate every
sequence over and over again, but keep it in a map/array (as suggested
by Rafael and me). I've found some Euler puzzles are impossible to solve
without this technique.
P.S.: If you're really going for speed, compile (not interpret) the code
(using -O -fvia-C, and there's some more stuff in the manual) using the
latest greatest version of GHC.
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