- Haskell-Cafe - Haskell.org

Hoogle and Network.Socket
by Felix Martini 19 Feb '09

19 Feb '09

The Network.Socket module works fine on Windows. The original Winsock implementation was based on the Berkeley sockets api.

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Re: [Haskell-cafe] How to create an online poll
by gregg reynolds 19 Feb '09

19 Feb '09

I.e. war, plague.famine. etc. gregg reynolds <dev(a)mobileink.com> wrote: >But what about the side effects? > >Rick R <rick.richardson(a)gmail.com> wrote: > >>I'm sure Premier Election Solutions (formerly Diebold) can provide us with >>an online voting solution. >>Their value-add services allows us to set the outcome beforehand, so, in >>effect, the the voting process will be determinate. Which is certainly of >>interest to Haskell coders. >> >> >>On Wed, Feb 18, 2009 at 4:05 PM, Max Rabkin <max.rabkin(a)gmail.com> wrote: >> >>> On Wed, Feb 18, 2009 at 10:40 PM, Anton van Straaten >>> <anton(a)appsolutions.com> wrote: >>> > There's also the Condorcet Internet Voting Service: >>> > >>> > http://www.cs.cornell.edu/andru/civs.html >>> >>> This looks like exactly what we need! Any objections? >>> >>> --Max >>> _______________________________________________ >>> Haskell-Cafe mailing list >>> Haskell-Cafe(a)haskell.org >>> http://www.haskell.org/mailman/listinfo/haskell-cafe >>> >> >> >> >>-- >>We can't solve problems by using the same kind of thinking we used when we >>created them. >> - A. Einstein >>_______________________________________________ >>Haskell-Cafe mailing list >>Haskell-Cafe(a)haskell.org >>http://www.haskell.org/mailman/listinfo/haskell-cafe

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Re: [Haskell-cafe] Haskell.org GSoC
by Daniel Kraft 19 Feb '09

19 Feb '09

Hi, sylvain wrote: > In my humble opinion, Haskell presently fall short of its promises > because it does not embed theorem proving. Quickcheck-like testing is > truly great, but can not replace proofs to produce bug free software. > > With use of equational reasoning + induction, one can already prove a > huge amount of useful properties of an Haskell program [1]. this sounds like a really interesting project to me... Especially as I'm doing maths instead of CS as main subject (and it is simply inherently interesting :D). > theorem : ( xs :: [a], ys :: [a], f :: a -> b) => > length (map f (xs ++ ys )) = length xs + length yx > proof > length (map f (xs ++ ys )) = > length (xs ++ ys) = {- use length++ -} > length xs ++ length ys That's of course nice, but I'm at the moment not yet convinced something like this could be more or less easily implemented also for larger programs; and, I don't see from your example how the real implementation of the program should play in. Do you expect that Haskell figures out from the implementation that (map f) does not alter a lists length? Or should this be an already available theorem within the Prelude? I guess it should be the former, as otherwise the whole proofing seems to be just documentation, without real connection to the Haskell code. But in this case, I wonder whether something like that can be successfully done on more sophisticated code, and especially done as part of a GSoC project... But I guess with a competent mentor and clearly defined goals it should be possible. But all in all, as stated above, this could be really interesting :) Thanks for this suggestion and your ideas! Daniel -- Done: Arc-Bar-Cav-Ran-Rog-Sam-Tou-Val-Wiz To go: Hea-Kni-Mon-Pri

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Memory
by Jeff Douglas 19 Feb '09

19 Feb '09

Hello All, The kind people at #haskell suggested I come to haskell-cafe for questions about haskell performance issues. I'm new to haskell, and I'm having a hard time understanding how to deal with memory leaks. I've been playing with some network server examples and I noticed with each new connection, the memory footprint increases by about 7k However, the leaks don't seem to have anything to do with the networking code. Actually I get a huge leak just from using using 'forever'. > import Control.Monad > import System.IO > > main = forever $ putStrLn "hi" When I run it for a few seconds with profiling... > total time = 0.36 secs (18 ticks @ 20 ms) > total alloc = 54,423,396 bytes (excludes profiling overheads) Can this be right?

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Returned mail: see transcript for details
by malcolm.wallace＠cs.york.ac.uk 19 Feb '09

19 Feb '09

Message could not be delivered

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Re: permuting a list
by Okasaki, C. DR EECS 18 Feb '09

18 Feb '09

The discussion of randomly permuting a list comes up every few years. Here's what I wrote last time (2005): "Clearly, you can do a perfect shuffle in O(N) time using mutable arrays, using the standard imperative algorithm. You can also do it in O(N) expected time using *immutable* arrays, using Haskell's bulk array operations. 1. Start with a list of length N. If N < 2, stop. 2. Pair each element with a random index in the range [1,2N] (or [0,2N-1]). 3. Use "accum" to create an array of size 2N, where slot I contains a list of all the elements paired with I. 4. Map the shuffle function recursively across the array to re-shuffle any slots that got more than one element. 5. Append all the slots together into the result list. If you leave out step 4, you get an algorithm that runs in O(N) worst-case time, rather than expected time, but you no longer have a perfect shuffle (although it might be good enough). Upping the size of the array from 2N to 3N or 4N will help reduce collisions, but will not entirely eliminate them. With step 4, you can imagine pathological cases where everything gets put in the same slot, but with a reasonable random number generator, it is vanishingly unlikely that you will have enough collisions to drive the cost higher than linear. Again, upping the size of the array from 2N to 3N or 4N makes this even more unlikely." Now, you can consider it cheating to say this is O(N) expected time because it uses O(N log N) random bits. Fair enough. It is O(N) to the same extent that the ordinary imperative algorithm is O(N), albeit expected rather than worst case. -- Chris

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Re: [Haskell-cafe] How to create an online poll
by gregg reynolds 18 Feb '09

18 Feb '09

Perhaps you are a subversive functor, hmm? We have monadic ways of conrolling you, fiend! Tellus who your natural tansformations are, or else! Andrew Wagner <wagner.andrew(a)gmail.com> wrote: >Help! Help! I'm being suppressed!! > >On Feb 18, 2009, at 5:05 PM, Rick R <rick.richardson(a)gmail.com> wrote: > >> I can't comment on any quantitative side effects, but the some >> intangible side effects include Distrustful Populace and >> MaliciousDissenters. However, if ghc is run with the - >> XUnscrupulousPolitics flag, those can be suppressed. >> >> On Wed, Feb 18, 2009 at 4:33 PM, gregg reynolds <dev(a)mobileink.com> >> wrote: >> I.e. war, plague.famine. etc. >> >> gregg reynolds <dev(a)mobileink.com> wrote: >> >> >But what about the side effects? >> > >> >Rick R <rick.richardson(a)gmail.com> wrote: >> > >> >>I'm sure Premier Election Solutions (formerly Diebold) can provide >> us with >> >>an online voting solution. >> >>Their value-add services allows us to set the outcome beforehand, >> so, in >> >>effect, the the voting process will be determinate. Which is >> certainly of >> >>interest to Haskell coders. >> >> >> >> >> >>On Wed, Feb 18, 2009 at 4:05 PM, Max Rabkin <max.rabkin(a)gmail.com> >> wrote: >> >> >> >>> On Wed, Feb 18, 2009 at 10:40 PM, Anton van Straaten >> >>> <anton(a)appsolutions.com> wrote: >> >>> > There's also the Condorcet Internet Voting Service: >> >>> > >> >>> > http://www.cs.cornell.edu/andru/civs.html >> >>> >> >>> This looks like exactly what we need! Any objections? >> >>> >> >>> --Max >> >>> _______________________________________________ >> >>> Haskell-Cafe mailing list >> >>> Haskell-Cafe(a)haskell.org >> >>> http://www.haskell.org/mailman/listinfo/haskell-cafe >> >>> >> >> >> >> >> >> >> >>-- >> >>We can't solve problems by using the same kind of thinking we used >> when we >> >>created them. >> >> - A. Einstein >> >>_______________________________________________ >> >>Haskell-Cafe mailing list >> >>Haskell-Cafe(a)haskell.org >> >>http://www.haskell.org/mailman/listinfo/haskell-cafe >> >> >> >> -- >> We can't solve problems by using the same kind of thinking we used >> when we created them. >> - A. Einstein >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe

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Re: [Haskell-cafe] How to create an online poll
by gregg reynolds 18 Feb '09

18 Feb '09

Ok, that might protect us against the 7 plagues, so I'm not so worried about locusts. But what about Java, PHP etc. Is the monad sufficient protection against ultra-supernatural evil? Andrew Wagner <wagner.andrew(a)gmail.com> wrote: >Just wrap it in a ReallySafeWePromiseMonad > >2009/2/18 gregg reynolds <dev(a)mobileink.com> > >> I.e. war, plague.famine. etc. >> >> gregg reynolds <dev(a)mobileink.com> wrote: >> >> >But what about the side effects? >> > >> >Rick R <rick.richardson(a)gmail.com> wrote: >> > >> >>I'm sure Premier Election Solutions (formerly Diebold) can provide us >> with >> >>an online voting solution. >> >>Their value-add services allows us to set the outcome beforehand, so, in >> >>effect, the the voting process will be determinate. Which is certainly of >> >>interest to Haskell coders. >> >> >> >> >> >>On Wed, Feb 18, 2009 at 4:05 PM, Max Rabkin <max.rabkin(a)gmail.com> >> wrote: >> >> >> >>> On Wed, Feb 18, 2009 at 10:40 PM, Anton van Straaten >> >>> <anton(a)appsolutions.com> wrote: >> >>> > There's also the Condorcet Internet Voting Service: >> >>> > >> >>> > http://www.cs.cornell.edu/andru/civs.html >> >>> >> >>> This looks like exactly what we need! Any objections? >> >>> >> >>> --Max >> >>> _______________________________________________ >> >>> Haskell-Cafe mailing list >> >>> Haskell-Cafe(a)haskell.org >> >>> http://www.haskell.org/mailman/listinfo/haskell-cafe >> >>> >> >> >> >> >> >> >> >>-- >> >>We can't solve problems by using the same kind of thinking we used when >> we >> >>created them. >> >> - A. Einstein >> >>_______________________________________________ >> >>Haskell-Cafe mailing list >> >>Haskell-Cafe(a)haskell.org >> >>http://www.haskell.org/mailman/listinfo/haskell-cafe >> >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe >> >>

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Re: [Haskell-cafe] How to create an online poll
by gregg reynolds 18 Feb '09

18 Feb '09

But what about the side effects? Rick R <rick.richardson(a)gmail.com> wrote: >I'm sure Premier Election Solutions (formerly Diebold) can provide us with >an online voting solution. >Their value-add services allows us to set the outcome beforehand, so, in >effect, the the voting process will be determinate. Which is certainly of >interest to Haskell coders. > > >On Wed, Feb 18, 2009 at 4:05 PM, Max Rabkin <max.rabkin(a)gmail.com> wrote: > >> On Wed, Feb 18, 2009 at 10:40 PM, Anton van Straaten >> <anton(a)appsolutions.com> wrote: >> > There's also the Condorcet Internet Voting Service: >> > >> > http://www.cs.cornell.edu/andru/civs.html >> >> This looks like exactly what we need! Any objections? >> >> --Max >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe >> > > > >-- >We can't solve problems by using the same kind of thinking we used when we >created them. > - A. Einstein >_______________________________________________ >Haskell-Cafe mailing list >Haskell-Cafe(a)haskell.org >http://www.haskell.org/mailman/listinfo/haskell-cafe

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Haskell users in the Houston area??
by Galchin, Vasili 18 Feb '09

18 Feb '09

Hello, Are there Haskell users in the Houston area? Regards, Vasili

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