[Haskell-cafe] Being impure within a 'pure' function

[Daniel K.]

Well, thanks to all of you.

Daniel

2009/4/23 Daniel Fischer <daniel.is.fischer at web.de>

> Am Donnerstag 23 April 2009 14:15:16 schrieb Max Rabkin:
> > On Wed, Apr 22, 2009 at 10:38 AM, Daniel K. <anmeldemails at gmail.com>
> wrote:
> > > Dijkstra's algorithm ... relies heavily on mutating arrays
> >
> > Well, the imperative implementation does.
> >
> > > Not mutating the underlying arrays would probably result in poor
> > > performance.
> >
> > Indeed. Non-mutable arrays are not very performant for mutations.
> > Tree-like data structures Are Your Friend.
> >
> > I've never compared the performance of an ST-based implementation with
> > a set/map based algorithm, but I've often found the latter usably
> > performant.
>
> I have occasionally, and I can confirm that often set/map based algorithms
> give quite
> usable performance. But usually ST-based implementations are significantly
> faster.
> If the algorithm demands a lot of updates and performance is important, I
> recommend
> sacrificing the ease and elegance of coding with sets/maps for ST's uglier
> but faster code
> (but verify that set/map performance is unsatisfactory first).
>
> >
> > --Max
>
>
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