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Stackage Haddocks extremely slow
by aditya siram 19 Oct '17

19 Oct '17

Hi all, I've noticed that lately Stackage's Haddock searches have been extremely slow; for example https://www.stackage.org/haddock/lts-9.9/base-4.9.1.0/Prelude.html#v:foldl took almost 8 seconds to pull up on my machine. Is anyone else seeing this? Thanks! -deech

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Re: [Haskell-cafe] [Haskell] Hack “Importify” by Serokell During #Hacktoberfest!
by Henning Thielemann 18 Oct '17

18 Oct '17

On Wed, 18 Oct 2017, Gints Dreimanis wrote: > All of us love to read explicit import lists (especially in an unknown > module), but we all hate to write and maintain them. You won't have many explicit import lists if you design the function names for qualified imports.

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Unused type-classes triggering a recompilation?
by Saurabh Nanda 18 Oct '17

18 Oct '17

Hi, We're trying to optimise the way lenses are built and imported in our project (there are 500+ of them!) . In the simplified version that I have presented below, whenever a new HasX class is added to the LensClasses module, both User & Main end up getting recompiled even though they have nothing to do with the newly added type-class. I've read and re-read "Recompilation Avoidance" [1], but haven't been able to figure out why this would be happening. PS: To work-around this issue we've had to give each HasX class an independent module of its own. We specifically import only those which are required (all of this is done via a code-gen tool). This has resulted in an explosion of modules and is probably causing slow-down of our build process [2] *LensClasses.hs:* {-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances #-} module LensClasses where import Control.Lens class HasName s a | s -> a where name :: Lens' s a class HasEmail s a | s -> a where email :: Lens' s a class HasAge s a | s -> a where age :: Lens' s a *User.hs (which defines a few lenses for the User record):* {-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, TypeSynonymInstances, FlexibleInstances #-} module User ( module User , HasName(..) , HasEmail(..)) where import LensClasses(HasName(..), HasEmail(..), HasVariantName(..)) data User = User { _userName :: String , _userEmail :: String } deriving (Eq, Show) instance HasName User String where {-# INLINE name #-} name fctor (User name_ email_) = fmap (\dragon -> User dragon email_) (fctor name_) instance HasEmail User String where {-# INLINE email #-} email fctor (User name_ email_) = fmap (\dragon -> User name_ dragon) (fctor email_) *Main.hs (the final call site/s):* module Main where import Control.Lens import User main :: IO () main = do let u = User "saurabh" "saurabhnanda(a)gmail.com" putStrLn $ u ^. name [1] https://ghc.haskell.org/trac/ghc/wiki/Commentary/Compiler/RecompilationAvoi… [2] https://www.reddit.com/r/haskell/comments/76zljl/hotswapping_haskell_at_fac…

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NYC Haskell Developer Position
by Christopher Lewis 18 Oct '17

18 Oct '17

Karamaan Group, is an investment firm based in Manhattan. We are looking for an outstanding software developer to develop tools for financial analysis and knowledge management. Since we are investors and not traders, our focus is not on building trading systems, but on business and data analysis. We strongly value people who take pride in their work and have a craftsman’s dedication to building bespoke products. Our ideal candidate is an experienced software developer with a penchant for abstraction and analysis, a solid sense of organization, and an ability to communicate and persuade. While we are looking for a candidate who demonstrates an intense focus on quality, she also needs a master engineer’s intuition on how to make trade offs that are a necessary part of day-to-day software development. Candidates should have some formal training in a quantitative field and a keen interest in building robust and elegant software. This is a high-impact, high-visibility position where successful candidates will be entrusted with a lot of responsibility for products that have a direct effect on the P&L of the firm and influence on our workflow. The ideal candidate will have production experience with Haskell or another functional language, relational databases and relational data modeling, Python, and Java. Additionally, as this is a startup environment, the ideal candidate will be comfortable filling many different technology roles, and contributing to the success of the firm wherever they can, not just in agreement with their job description. Remote work is not an option for this position. Karamaan Group is an investment adviser and manager catering to family offices and institutional investors. We value innovative thinking, encourage an entrepreneurial atmosphere, and enjoy spirited discussions. Please send your CV and cover letter to recruitment at karamaan dot com. Please do not reply to the original poster.

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ANN: New Full Platform Build of Haskell Platform 8.2.1 for Mac
by Gershom B 18 Oct '17

18 Oct '17

Thanks to some intrepid sleuthing by Albert Y. C. Lai, we realized there was a serious problem in the full (not core) builds of HP for Mac and Linux (not Windows). If you've seen lots of "unusable due to shadowed dependencies" errors on packages that came with full 8.2.1 platform installs on those systems, this is likely why. We should have tested better and caught this, and I'm sorry for the trouble it has caused. I've released a new build of the full mac installer, and updated the hash on the site. A new generic-linux build should follow soon. Regards, Gershom P.s. For those interested, the technical details are at https://github.com/haskell/haskell-platform/issues/285 -- in brief, the platform had done builds using inplace conf files but deployed using proper target package-conf files. This worked just fine until the new abi-depends machinery was introduced for better computing dependency mismatches (https://phabricator.haskell.org/D2846 is one place to start reading about that). That new machinery then recognized that different abis were generated for the inplace conf than the target conf, and things went screwy. But the problem here isn't with those changes -- it's with our inadequate testing that should have caught when things went wrong and alerted us that we needed to step back and fix things earlier, and the responsibility for that is all on me.

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Re: [Haskell-cafe] [Call for Contributions] Haskell Communities and Activities Report, November 2017 edition (33rd edition)
by Karim Salah 17 Oct '17

17 Oct '17

Asteroids Name: Kareem salah (FCIH) status: stable, actively developed participants: mostafa hazem, khaled hesham, belal ibrahim Asteroids is Haskell version of the known asteroids game which was developed with many programing languages as startup project the main aim of the game is to score the highest score by shooting the coming asteroids while avoiding them (just remember u have only three spaceships) the game is simulating the space physics so don't think it is so easy. the game following up the original game rules beside that we added a multi-player system to invite your friends to join your campaign. our team found it a good opportunity to develop a version using Haskell and by using the lazy programming techniques in our favor we were able to provide a stable fps a stable version of the game was released and it's free to download and play we are looking forward for active contributions in order to add versus system, rewarding system and progression system so, forward contributions related to code refinement or adding features is welcomed url : https://github.com/kareem2048/Asteroids

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[Announce] ZuriHac 2018 - 8-10 June in Zurich, Switzerland
by Jasper Van der Jeugt 17 Oct '17

17 Oct '17

It is our pleasure to announce that, like in previous years, ZuriHac will also take place in 2018 -- from Friday June 8th to Sunday the 10th. It will be hosted at the Hochschule Rapperswil right besides the beautiful lake Zurich, like last year. The Zurich Haskell Hackathon is a free (as in beer), international, grassroots collaborative coding festival whose goal is to expand the community and to build and improve Haskell libraries, tools, and infrastructure. This is already the 7th Haskell Hackathon in Zurich! This year, we will enjoy keynotes from: - Niki Vazou - Edward Kmett - Stephen Diehl More keynote speakers will be announced. This event is open to any experience level, from beginners to gurus. This year, Julie Moronuki, co-author of Haskell Programming from first principles [1], has kindly agreed to teach a beginners course in one of the classrooms we have available. Additionally, there will be mentors on site whom you can directly approach during the whole event with any Haskell-related question you have. This is a great opportunity to meet your fellow Haskellers in real life, find new contributors for your project, improve existing libraries and tools or even start new ones! We will have space for 300 attendees. Registration will open on 6th of December. You can find more information on our website [2]. We would also like to thank our sponsors Digital Asset [3] and HSR [4] for supporting this great event! Looking forward to see you there, the Zurich HaskellerZ meetup group [1]: https://www.goodreads.com/book/show/25587599-haskell-programming [2]: https://zurihac.info/ [3]: https://digitalasset.com/careers.html [4]: https://www.hsr.ch/

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Exposing a GADT-provided dictionary
by Kosyrev Serge 17 Oct '17

17 Oct '17

Good day, cafe! I found a way to expose a GADT-provided dictionary, but I don't quite like it: > {-# LANGUAGE GADTs, RankNTypes #-} > > import Data.Function ((&)) > > class HasDict a where > > data GADT a where > G1 :: HasDict a => a -> GADT a > -- ... > Gn :: HasDict a => a -> GADT a > > -- | Execute @body with the dictionary for HasDict extracted from the > -- GADT. > withGADTDict :: > (forall b. (b ~ a, HasDict b) => GADT b -> c) -> GADT a -> c > withGADTDict body x = x & case x of > G1 _ -> body > -- ... > Gn _ -> body The problem is in withGADTDict's proportionality to the number of GADT's clauses, as it is somewhat anti-modular. Is that the only light-weight option? I can imagine there is a way to leverage generic programming, but that's a bit heavy.. -- с уважениeм / respectfully, Kosyrev Serge PGP Key ID: 3F62F118E38BED6D -- “Most deadly errors arise from obsolete assumptions.” -- Frank Herbert, Children of Dune

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Re: [Haskell-cafe] Network Connect Timeouts
by Chris Wong 16 Oct '17

16 Oct '17

Hi Mark, >From reading the source code for *runTCPClient* [1], it looks like a thin wrapper around *getSocketFamilyTCP* and *close*. It should be sufficient to copy that definition into your project and wrap the *getSocketFamilyTCP* call in a *timeout*. You might need to import *Data.Streaming.Network.Internal* to get access to the *AppData* constructor. Hope this helps! [1] https://hackage.haskell.org/package/streaming-commons-0.1.18/docs/src/Data-… On Sun, Oct 15, 2017 at 9:08 AM, Mark Fine <mark.fine(a)gmail.com> wrote: > Hi Chris, > > In my application, I'm using *Data.Conduit.Network* from *conduit-extra* directly > (*Data.Streaming.Network* from *streaming-commons* indirectly). The > timeout I'm interested in managing is the connection establishment timeout > - how long does the connect call wait to establish a connection. I haven't > been able to figure out how to control this outside of applying a > non-conditional timeout to the connect call (which is a timeout on the > lifetime of a connection, not a timeout on the establishment of a > connection). Thanks! > > Mark > > On Sat, Oct 14, 2017 at 3:09 AM, Chris Wong <lambda.fairy(a)gmail.com> > wrote: > >> Hi Mark, >> >> What networking library are you using? >> >> There should be a lower level interface which allows for managing the >> lifetime of a connection by hand. >> >> Chris >> >> On Oct 14, 2017 15:17, "Mark Fine" <mark.fine(a)gmail.com> wrote: >> >>> I'd like a configurable network connect timeout. Has anyone solved this >>> reasonably? >>> >>> *System.Timeout.timeout* times out connections, but works on the >>> granularity of the life of the connection. Is there a reasonable way to >>> configure a timeout around just establishing the connection? Maybe >>> something like a conditional timeout that enables an action to disable the >>> timeout once it expires? >>> >>> As a workaround, I'm spinning trying to successfully connect first >>> before trying to connect for real: >>> >>> -- | Try the TCP connection and see if you can connect... >>> -- >>> tryTCPClient :: Int -> ClientSettings -> IO () >>> tryTCPClient microseconds settings = do >>> ok <- newIORef False >>> void $ timeout microseconds $ runTCPClient settings $ const $ >>> writeIORef ok True >>> ok' <- readIORef ok >>> unless ok' $ >>> tryTCPClient microseconds settings >>> >>> -- | Wrap runTCPClient with a connect timeout. >>> -- >>> -- Tries the TCP connection first, and the runs the regular runTCPClient. >>> -- Of course, this only enforces a TCP connect timeout on the first >>> connect. >>> -- The second TCP connect has no timeout :( >>> -- >>> runTCPClient' :: Int -> ClientSettings -> (AppData -> IO a) -> IO a >>> runTCPClient' microseconds settings action = do >>> tryTCPClient microseconds settings >>> runTCPClient settings action >>> >>> I've also tried running the *tryTCPClient* in its own thread >>> concurrently with *runTCPClient* and throwing an exception if it can't >>> connect in *microseconds*. None of these offer an actual true >>> connection establishment timeout. >>> >>> Has anyone found a way to solve this? Thanks! >>> >>> Mark >>> >>> >>> >>> _______________________________________________ >>> Haskell-Cafe mailing list >>> To (un)subscribe, modify options or view archives go to: >>> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe >>> Only members subscribed via the mailman list are allowed to post. >>> >> > -- Chris Wong (https://lambda.xyz) "I had not the vaguest idea what this meant and when I could not remember the words, my tutor threw the book at my head, which did not stimulate my intellect in any way." -- Bertrand Russell

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Re: [Haskell-cafe] Your haskell-cafe message [Was: random library]
by jpaugh＠gmx.com 16 Oct '17

16 Oct '17

Ian, Thanks for the note. I work for a secondary school, so that explains the block. I'll keep that in mind, and send mail from home. Thanks, Jon On October 14, 2017 12:29:03 PM CDT, Ian Zimmerman <itz(a)very.loosely.org> wrote: >On 2017-10-10 22:46, jpaugh(a)gmx.com wrote: > >> Interesting library! Here's a link: >> >http://hackage.haskell.org/package/DRBG-0.5.5/docs/Crypto-Random-DRBG.html > >The address from which you posted this is listed by spamhaus: > > ahiker!2 itz$ rblcheck 172.56.6.158 >172.56.6.158 not listed by sbl.spamhaus.org >172.56.6.158 listed by xbl.spamhaus.org >172.56.6.158 listed by pbl.spamhaus.org >172.56.6.158 not listed by bl.spamcop.net >172.56.6.158 not listed by psbl.surriel.com >172.56.6.158 not listed by dul.dnsbl.sorbs.net > >This often happens when people post from cafes and similar, and if this >is the case here not much can be done, unfortunately - other than >perhaps trying a different cafe next time :-) > >-- >Please don't Cc: me privately on mailing lists and Usenet, >if you also post the followup to the list or newsgroup. >Do obvious transformation on domain to reply privately _only_ on >Usenet. -- Sent from my Android device with K-9 Mail. Please excuse my brevity.

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