- Haskell-Cafe - Haskell.org

Video chair at ICFP
by Johan Jeuring 13 Apr '14

13 Apr '14

Dear people, We are busy organising ICFP 2014, which will happen together with the Haskell Symposium and many other events in Göteborg in Sweden from August 31 until September 6 2014. I am looking for a Video chair to organise the recording of the events on video. Tasks - prepare the video recording of the events: equipment (camera's, software, microphones?), required post-processing, ... - instruct student-volunteers in assisting the recording process - oversee the post-processing of the recordings, and the uploads Budget - we have some budget available for buying or renting equipment for the video recordings, or we can pay you for you bringing your own equipment - we will defray your costs for travelling to Göteborg, staying in Göteborg, and attending ICFP 2014 and affiliated events Please contact me if you are interested in this position/task, With kind regards, Johan Jeuring General chair for ICFP 2014

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warp vs scotty + some benchmark numbers
by Miro Karpis 13 Apr '14

13 Apr '14

Hi, I'm trying to make a small benchmarking for warp and scotty (later with json/no-json text performance test). My client is a Qt c++ application. I made a minimum code in both Haskell and C++. The problem is the numbers I'm getting. (Benchmark::pong-warp) - total requests: 10000 , send/received in msec: 3848 (Benchmark::pong-scotty) - total requests: 10000 , send/received in msec: 3814 Only sending 10k requests from my c++ client takes around 1 sec. What I don't understand is: a) how is it possible that scotty is so close to warp (in this run it even wins)? b) 10k requests I'm getting in approximately 4 seconds. Here<http://www.yesodweb.com/blog/2011/03/preliminary-warp-cross-language-benchm…>is one 2 years old benchmark with 80k/second. Why is there so big difference? I'm running on macbook-pro 16g, 2.3 GHz Scotty and warp is compiled with: -O2 -threaded --scotty import Web.Scotty import Data.Monoid (mconcat) main = scotty 3005 $ do get "/" $ do text "pong" --warp import Network.Wai(responseLBS, Application) import Network.HTTP.Types(status200) import Network.Wai.Handler.Warp (run) app :: Application app _ = return $ responseLBS status200 [("Content-Type", "text/plain")] "pong" main :: IO () main = do let port = 3000 putStrLn $ "Listening on port " ++ show port run port app --c++ client sample (Qt) simStart = QDateTime().currentMSecsSinceEpoch(); for(int i=0; i<requests; i++){ QNetworkReply *reply = manager->get(QNetworkRequest(url)); QEventLoop eventLoop; QObject::connect(manager, SIGNAL(finished(QNetworkReply *)), &eventLoop, SLOT(quit())); eventLoop.exec(); QObject::disconnect(manager, SIGNAL(finished(QNetworkReply *)), &eventLoop, SLOT(quit())); } qDebug() << "(Benchmark::pong) - total requests: " << requests << ", send in msec: " << (QDateTime().currentMSecsSinceEpoch()-simStart); cheers, miro

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Simple OverloadedLists question
by Konstantine Rybnikov 13 Apr '14

13 Apr '14

Hi! I wanted to check out great new OverloadedLists [0] feature, but got an error as in [1]. What am I doing wrong? Thanks. [0]: https://www.haskell.org/ghc/docs/7.8.1/html/users_guide/type-class-extensio… [1]: https://gist.github.com/k-bx/10574806

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OverloadedLists pattern-matching
by Konstantine Rybnikov 13 Apr '14

13 Apr '14

Continuing playing with OverloadedLists and GHC 7.8.2. For this code: ``` {-# LANGUAGE OverloadedLists #-} {-# LANGUAGE OverloadedStrings #-} {-# LANGUAGE TypeFamilies #-} import Data.Map import Data.Text import GHC.Exts instance (Ord k) => IsList (Map k v) where type Item (Map k v) = (k,v) fromList = Data.Map.fromList toList = Data.Map.toList main :: IO () main = do let m = [("foo", 1), ("bar", 2)] :: Map Text Int putStrLn "My map looks like this:" case m of [] -> putStrLn "impossible!" [x,_] -> putStrLn $ "ok, some random elem is: " ++ show x print m ``` I have this output from compiler: ``` root@b575c8a9c84b:~/overloaded_lists# cabal build --ghc-options="-fforce-recomp" Building overloaded-lists-0.1.0.0... Preprocessing executable 'overloaded-lists' for overloaded-lists-0.1.0.0... [1 of 1] Compiling Main ( src/Main.hs, dist/build/overloaded-lists/overloaded-lists-tmp/Main.o ) src/Main.hs:19:5: Warning: Pattern match(es) are non-exhaustive In a case alternative: Patterns not matched: _ src/Main.hs:9:10: Warning: Orphan instance: instance Ord k => IsList (Map k v) [1 of 1] Compiling Main ( src/Main.hs, dist/build/overloaded-lists/overloaded-lists-tmp/Main.o ) src/Main.hs:19:5: Warning: Pattern match(es) are non-exhaustive In a case alternative: Patterns not matched: _ src/Main.hs:9:10: Warning: Orphan instance: instance Ord k => IsList (Map k v) Linking dist/build/overloaded-lists/overloaded-lists ... ``` Couple things: 1. It shows same warnings two times. Is this a bug? 2. It doesn't seem to be that warning that pattern "_" wasn't matched should be there. Should I also create a bug report? Thank you!

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Docker image for GHC 7.8.2
by Konstantine Rybnikov 13 Apr '14

13 Apr '14

For people like me who would like to try out 7.8.2, but don't want to make new creative ways of making your system be able to handle multiple ghc/cabal/etc, I created a docker image. Source code, instructions how to build image yourself, or just pull/run it are here: https://bitbucket.org/k_bx/docker-ghc-7.8 Thanks. // I will make a github mirror once hg-git is fixed back by new dulwich lib release soon

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Dependencies (was Re: Patches for (abandoned?) pcre-light)
by Doug Burke 13 Apr '14

13 Apr '14

On Apr 12, 2014 9:10 PM, "Nikolay Amiantov" <nikoamia(a)gmail.com> wrote: > > Also, the second (unrelated) question would be: how can I find a package which depends on it in my project? I have found no way to dump a dependency tree in cabal. Is this the information that you want? http://packdeps.haskellers.com/ http://packdeps.haskellers.com/reverse Doug

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Feedback/Ideas for a Master Thesis about creating a Querying Tool for Hackage
by Victor Nithander 13 Apr '14

13 Apr '14

Hi, My name is Victor Nithander and I am currently doing my Master Thesis at the Computer Science and Engineering department at Chalmers in Gothenburg and would like to ask you for some help. My Master Thesis is about creating a querying tool for Hackage written in Haskell and I would like to know what kind of features you would like the querying tool to have. My plan is to design and implement an embedded language for queries to be expressed in and then implement a backend which accordingly takes care of those queries. I then plan to packet the tool as a package using Cabal and upload it to Hackage. Any feedback/ideas on features or other things about the tool would be greatly appreciated as I want to make a tool which benefits the community as much as possible. Examples of queries I'm thinking of to implement is: - Which language features (such as typeclass instances) does a certain package use? - How many packages uses a certain language feature? - Which packages does a certain package depend on? - Which packages depends on a certain package? Of course, this in no way limits what other type of queries could be made. I will also post this at the Haskell Section of reddit at http://www.reddit.com/r/haskell/, sorry for the redundancy. Feel free to respond to this either at this mailing list, at reddit, or as a personal email at nithande(a)student.chalmers.se though I think the best would be to have an open discussion about it. Thanks in advance! / Victor

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Re: [Haskell-cafe] Seems a wrong implementation of Graham Scan in Haskell Wiki
by Yang Leo 12 Apr '14

12 Apr '14

Ah so that’s how a mailing list works.. Sorry for my stupidness... On Apr 12, 2014, at 1:08 AM, Kim-Ee Yeoh <ky3(a)atamo.com> wrote: > > On Sat, Apr 12, 2014 at 12:01 AM, Yang Leo <jeremyrobturtle(a)gmail.com> wrote: > I’ve updated the Haskell wiki now. I haven’t learnt how to do unit tests in Haskell yet, > any tests on my implementations would be welcomed. > > wikipage: http://www.haskell.org/haskellwiki/Graham_Scan_Implementation > > Would you mind forwarding to the haskell-cafe mailing list as well? > > So that everyone else is kept updated? > > -- Kim-Ee

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Haddock markup questions
by Christiaan Baaij 11 Apr '14

11 Apr '14

Hello list, I have two questions regarding proper markup for my haddock documentation. I'm using the latest released haddock, version 2.14.2. The first is about deprecation pragma's and operators usint '<' and '>' I have the following deprecation message: > {-# DEPRECATED Comp "Use 'Applicative' interface and ('<^>') instead" #-} Haddock however generates the following: http://christiaanb.github.io/clash-prelude/CLaSH-Prelude.html#t:Comp Where 'Applicative' gets a proper link to the applicative type class... but '<^>' is translated to a link to '^'... which is a page that doesn't exists. I can get haddock to not generate a link using: > > {-# DEPRECATED Comp "Use 'Applicative' interface and ('\\<^\\>') instead" #-} But that's unwanted, as those backslashes show up in GHC(i) messages. So: how do I get haddock to not parse my '<^>' operator as a link/URL? My second question is again about getting links to operators in general. If you take a look at, e.g., http://hackage.haskell.org/package/base-4.7.0.0/docs/Control-Applicative.ht… You can see that proper documentation links are generated to the '<*>' and such operators. However, if you take a look at the documention I tried to generate for my library: http://christiaanb.github.io/clash-prelude/CLaSH-Signal-Implicit.html#v:-60… You can see that the referenced '^>' operator does not get a proper link. So my question: how do I get haddock to create proper links for my referenced operators. I should note that I create haddock docs using 'cabal haddock' instead of calling haddock directly. Best regards, Christiaan

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[ANN] Yi 0.8
by Mateusz Kowalczyk 11 Apr '14

11 Apr '14

We're pleased to announced Yi 0.8! While this isn't a huge release, there are some nice fixes and breaking changes compared to 0.7.0. Please note that 0.7.1 and 0.7.2 were just maintenance releases so these are lumped under this announcement. What I think is most notable is removal of Yi.Prelude, dropping GHC 7.4 support, making Yi work with GHC 7.8.1 (and soon 7.8.2 when that comes out sometime today), moving from data-accessor to lens and finally dropping the dead front-ends. Please visit us at https://github.com/yi-editor/yi Relevant part of the CHANGELOG: 0.8.0 ----- * This release works with GHC 7.8.1. * And doesn't work with GHC 7.4. * Lens is now used instead of data-accessor. Migration was mostly mechanical, patches for more idiomatic lens usage are welcome. * Yi.Prelude was getting complaints over the years so it's now gone. * Commandline flag for choosing config directory now works. * Vte and Cocoa (issue #481) frontends that were abandoned for years are removed. If you want to revive these or make new frontends (Qt, EFL, SDL, threepenny-gui, etc), patches are welcome! * Test files no longer make case sensitive filesystems mad (issue #458). * Yi no longer eats (20 x filesize) memory when opening a file. * Other bugfixes and usability tweaks here and there. Emacs-specific changes: * Dynamic reconfiguring yi with "M-x reload" now works (issue #515). * Cancel incremental search on cursor movement/return (issue #499). * Remove binding to cabal configure from emacs keymap (issue #522). * Bind M-{ and M-} to jump between paragraphs (issue #106). * Prompt the user for comment style when it's missing (issue #413). Vim2-specific changes: * C-n completion now uses words from all open buffer instead of just current one. * Introduced :buffer, :buffers and :bdelete commands and C-^ and C-6 normal mode bindings. * Meta modifier is now available for use in Vim2 bindings. * :s(ubstitute) now works with delimiters other than '/' (issue #461). * Introduced :cabal command. * More tests. 0.7.2 ----- * This is a maintenance release, upper bound set for QuickCheck. 0.7.1 ----- * This is a maintenance release, yi.cabal got cleaned up a little and dependencies got bumped, some problematic upper bounds were removed. Thanks! -- Mateusz K.

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