[Haskell-cafe] Can Haskell outperform C++?

[Thomas DuBuisson]

On Mon, May 21, 2012 at 7:53 AM, Yves Parès <yves.pares at gmail.com> wrote:
>> Not necessarily.  For example the 'nub' function from Data.List could be
>> much faster.  Unfortunately this would also change its type.  O(n²)
>> complexity is really the best you can get with the Eq constraint.
>
> Why not in that kind of cases provide a second function (named differently),
> together with the original function, and specify they're differences (i.e.
> wrt performances) in the doc?
> It seems like a pretty quick and honest trade-off to me.


WRT nub, Bart Massey did exactly this in his "nubOrd" proposal.  He
obtained consensus then failed to finish the ticket [1].  If this
particular case is of interest to you or anyone else then I suggest
you take the patches, re-propose and see it finished.  If you are
interested in this general category of issue, I think this is a case
study in how costly even our seemingly light weight proposals process
is in terms of proposer time investment.

Cheers,
Thomas

[1] http://hackage.haskell.org/trac/ghc/ticket/2717

>
> 2012/5/21 Ertugrul Söylemez <es at ertes.de>
>>
>> Ryan Newton <rrnewton at gmail.com> wrote:
>>
>> > I do think we have the opposite problem, however, in much Haskell code
>> > -- people are using the clean, obviously correct, but inefficient code
>> > even in standard library functions that really should be optimized
>> > like crazy!
>>
>> Not necessarily.  For example the 'nub' function from Data.List could be
>> much faster.  Unfortunately this would also change its type.  O(n²)
>> complexity is really the best you can get with the Eq constraint.  You
>> have to change to Ord for better performance.
>>
>> In other words:  Some optimizations change the semantics, and semantics
>> is taken very seriously in Haskell, for which I'm grateful.
>>
>>
>> Greets,
>> Ertugrul
>>
>> --
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