May 2009 - Haskell-Cafe

Re: A problem with par and modules boundaries...
by John Lato 22 May '09

22 May '09

Hi Mario, It looks like the parallelize function is getting inlined when it's in the same file, but not when it's in a separate file. Adding a {-# INLINE parallelize #-} pragma to the module with parallelize recovers all the performance for me. You could probably see exactly what's happening in more detail by going through the Core output. John Lato > Message: 23 > Date: Thu, 21 May 2009 22:59:51 -0400 > From: Mario Bla?evi? <mblazevic(a)stilo.com> > Subject: [Haskell-cafe] A problem with par and modules boundaries... > To: <haskell-cafe(a)haskell.org> > Message-ID: <.1242961191(a)magma.ca> > Content-Type: text/plain; charset="utf-8" > > I'll cut to the chase. The short program below works perfectly: when I compile it > with -O2 -threaded and run with +RTS -N2 command-line options, I get a nearly 50% > real-time improvement: > > $ time ./primes-test +RTS -N2 > 5001 > > real 0m9.307s > user 0m16.581s > sys 0m0.200s > > However, if I move the `parallelize' definition into another module and import > that module, the performance is completely lost: > > $ time ./primes-test +RTS -N2 > 5001 > > real 0m15.282s > user 0m15.165s > sys 0m0.080s > > I'm confused. I know that `par` must be able work across modules boundaries, > because Control.Parallel.Strategies is a module and presumably it works. What am > I doing wrong? > > >> module Main where >> >> import Control.Parallel >> import Data.List (find) >> import Data.Maybe (maybe) >> >> --import Parallelizable >> parallelize a b = a `par` (b `pseq` (a, b)) >> >> test :: Integer -> Integer -> Integer >> test n1 n2 = let (p1, p2) = parallelize >> (product $ factors $ product [1..n1]) >> (product $ factors $ product [1..n2]) >> in p2 `div` p1 >> >> factors n = maybe [n] (\k-> (k : factors (n `div` k))) >> (find (\k-> n `mod` k == 0) [2 .. n - 1]) >> >> main = print (test 5000 5001) >

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haskellnet
by Robert Wills 22 May '09

22 May '09

Hello, Yesterday I found myself wanting to clear out a spam-ridden pop account without downloading all the messages. Rather than just using Python's poplib, I thought I might look for a haskell solution and came across Haskellnet: http://darcs.haskell.org/SoC/haskellnet/ I ended up spending much of the afternoon getting it to compile and much of last night trying to get the pop library to actually work (the 'strip' method produced exceptions). It was a good learning experience (this was helpful: http://donsbot.wordpress.com/2007/11/14/no-more-exceptions-debugging-haskel…) I'm writing here because I'm wondering whether it would be worthwhile putting it up on hackage? From searching this list, there seem to have been a few times when people have stumbled across it but got frustrated when it didn't compile. If so, what's the protocol? Is the original author, Jun Mukai, still around? Thanks, Rob

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Putting unit tests in cabal files (Was Re: [Haskell-cafe] HUnit)
by Magnus Therning 22 May '09

22 May '09

On Fri, May 22, 2009 at 12:13 AM, Vasili I. Galchin <vigalchin(a)gmail.com> wrote: > Hello, > > I have some code with several test cases that use HUnit. I added hunit > as one of my cabal dependencies but cabal complained with: > > Setup: At least the following dependencies are missing: > hutil -any > > What am I doing incorrectly? Would you mind posting your .cabal file too? The reson I'm asking is that I've so far _never_ put any information about unit tests or quickcheck tests in my .cabal file, simply because I don't want the executables to be picked up by automatic package converters such as cabal2arch. Instead I have a makefile for building my test programs. If you have some way of keeping information about building of tests in your .cabal I'd be very interested in seeing it. /M -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus＠therning．org http://therning.org/magnus identi.ca|twitter: magthe

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HUnit
by Vasili I. Galchin 22 May '09

22 May '09

Hello, I have some code with several test cases that use HUnit. I added hunit as one of my cabal dependencies but cabal complained with: Setup: At least the following dependencies are missing: hutil -any What am I doing incorrectly? Thanks, Vasili

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ANN: TxtSushi 0.1
by Keith Sheppard 22 May '09

22 May '09

Hello Haskell Cafe I have released the first version of TxtSushi which is a collection of command line utils (written in haskell of course) for processing tab-delimited and CSV files. It includes a util for doing SQL SELECTs on flat files. This is my first haskell project and feedback of all kinds is appreciated. Home Page: http://www.keithsheppard.name/txt-sushi Darcs Repository: http://patch-tag.com/r/txt-sushi/home Issue Tracking: http://code.google.com/p/txt-sushi I would like to say thanks to the haskell-beginners contributors, the author of "Learn you a Haskell" and the author of the parsec library all of which were very helpful. Regards Keith

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Function Returning Type?
by jrw4 21 May '09

21 May '09

I wrote this function as I am just learning Haskell. What it does is it generates a list of all rational numbers between 0 and 1, but I only have it show the first 20. rationals n :: Integer -> String rationals n = (putStr . unlines . map show) (take n (nub [x % y | y <- [1..], x <- [1..y], x < y])) Now my problem is the type declaration, the first line. I get the error "Invalid type signature". I googled this error and I was not able to find out why it is giving it to me. I have also tried: rationals n :: Integer -> [Ratio] but it gives me the same error. Please someone point me in the right direction. Thanks. -- View this message in context: http://www.nabble.com/Function-Returning-Type--tp23658819p23658819.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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ANN: feed2twitter 0.2 & hackage2twitter 0.2.1
by Tom Lokhorst 21 May '09

21 May '09

To all the cool kids using the Twitter (and to anyone else): I'm happy to announce the first release of feed2twitter. Build on top of the excellent feed and hs-twitter packages, feed2twitter sends posts from a news feed to Twitter. The hackage2twitter executable is build on top of the feed2twitter library. It `tweets' the releases of new Hackage-packages. In the 3 days it has been running, it has already posted 70+ releases: http://twitter.com/Hackage - Tom Lokhorst http://hackage.haskell.org/cgi-bin/hackage-scripts/package/feed2twitter http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hackage2twitter

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Re: [Haskell-cafe] Haskell in 3 Slides
by Kalman Noel 21 May '09

21 May '09

Joe Fredette schrieb: > 3-4 slides imply 3-4 topics, so the question is what are the 3-4 biggest > topics in haskell? I would think they would be: > > * Purity/Referential Transparency > * Lazy Evaluation > * Strong Typing + Type Classes > * Monads If the goal is to be able to talk about different examples of Haskell code in the rest of the presentation, the big topic I'd choose would be called »How function definitions look like in Haskell«. Kalman

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Haskell philosophy question
by Vasili I. Galchin 21 May '09

21 May '09

Hello, I am confused between Haskell as delineated in the Haskell Report VS ghc "pragmas" which extend Haskell beyond the Haskell Report. I am sure I am not the first to ask. Caveat: on my part, I am not against innovation/extensions, but I don't like to see language "bloat". This is not a negative/pegorative statement .... just a challenging one. Kind regards, vasili

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Re: Re: [Haskell-cafe] what's the definition of "satisfy" and "<?>" ?
by Lee Duhem 21 May '09

21 May '09

On Thu, May 21, 2009 at 6:48 PM, z_axis <z_axis(a)163.com> wrote: > Sorry! I am a haskell newbie. then i will have a look at > Text.ParserCombinators.Parsec.Char Don't forget to CC your reply to the list, so other people on the thread will see your reply. lee

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