- Haskell-Cafe - Haskell.org

I would like to add haskell-russian@ mailing list to "User groups" wiki page
by Alexander Alexeev 07 May '14

07 May '14

Hello. Could someone add https://groups.google.com/forum/#!aboutgroup/haskell-russian ... to this wiki page http://www.haskell.org/haskellwiki/User_groups#Russia ... please? Or I could do it by myself if someone would create me an account at Haskell Wiki. Username I would like to have - eax (like @ Hackege). -- Best regards, Alexander Alexeev http://eax.me/

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Splicious is now accepting applications for alpha user trials
by Greg Meredith 07 May '14

07 May '14

Dear Haskellians and CurriedOnes, Splicious is now accepting applications for alpha user trials<http://www.splicious.net/> . To learn more about splicious, apart from that it is written in a higher-kinded functional language and makes extremely cool use of delimited continuations, please check out these links. - splicious and distributed identity<https://www.youtube.com/watch?v=Tz2pmVGgrG4> - splicious, BitCoin, content creation, curation, and sharing<https://www.youtube.com/watch?v=f700b6IHZcc> - Vlad Patryshev's review of splicious<https://www.youtube.com/watch?v=nRmu9-AL2OM> - The specialK white paper<https://docs.google.com/document/d/1aM5OIJWOyW89rHdUg6d9-YVbItdtxxiosP_fXZQ…> - A link to our crowd funding site<http://www.rockethub.com/projects/42500-splicious> Love to all, --greg -- L.G. Meredith Managing Partner Biosimilarity LLC 1219 NW 83rd St Seattle, WA 98117 +1 206.650.3740 http://biosimilarity.blogspot.com

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Cabal exit codes when work to be done
by Andrew Cowie 06 May '14

06 May '14

Is there a way to run e.g. `cabal install --only-dependencies` and have it return a non-zero exit code if, for instance, there IS something to do? I tried `--dry-run` but the exit code is still 0 if something is missing. [or have it return non-zero if there isn't work to do, or...] AfC Sydney

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Questions about Functor, Applicative, Monad
by Corentin Dupont 05 May '14

05 May '14

Hi everybody! Two questions in one: - When you define and instance of a Monad, why don't you get the Applicative and Functor instances for free? I seem that you can mechanically write them. - Do you have examples of things that are Functors but not Applicative? Applicative but not Monads? Tchuss Corentin

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extensible records - Vinyl - alternatives?
by Peter Althainz 05 May '14

05 May '14

Dear All, I'm searching a handsome library for handling large amounts of configuration data in a flexible manner. So to speak I want to use some kind of inheritance of data fields. I think this is where the extensible records discussion is a proper description of my use case. I've found 2 libraries making this work, so far: HList Vinyl I currently prefer Vinyl due to the complex types in HList, lens compatibiliy, named labels. (I love the HList and OOHaskel papers, but for practical use, I currently prefer Vinyl). What do you think, what is the best way nowadays to use extensible records? Is Vinyl a good choice from your point of view? regards Peter

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ANN: hsqml-0.3.0.0 supports Qt 5
by Robin KAY 05 May '14

05 May '14

Dear All, I would like to announce version 0.3.0.0 of the HsQML graphics library, a Haskell binding to the Qt Quick framework. The library allows you to write graphical applications where the front-end is written in Qt Quick's QML language (incorporating JavaScript) and the back-end is written in Haskell. The two layers are coupled together via a facility to define custom JavaScript objects through which QML code can call into Haskell and vice versa. Documentation including a brief tutorial is available on my web-site [1]. HsQML requires an installation of Qt 5 (including Qt Quick) present on your path. This is the first release to support Qt 5 and it has been a much requested feature. Several other new features are also introduced in this release, including support for marshalling lists and signalling property notifications. For more information, please see the release announcement [2]. The release is available for download from Hackage [3] along with a demo application implementing Nine Men's Morris [4] and some other sample programs [5]. Linux, Windows, and Mac OS platforms should all be supported. [1] http://www.gekkou.co.uk/software/hsqml [2] http://blog.gekkou.co.uk/2014/05/hsqml-0300-released-now-with-qt-5.html [3] http://hackage.haskell.org/package/hsqml-0.3.0.0 [4] http://hackage.haskell.org/package/hsqml-demo-morris-0.3.0.0 [5] http://hackage.haskell.org/package/hsqml-demo-samples-0.3.0.0 Regards, -- Robin KAY

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Quick question on Lens
by Corentin Dupont 04 May '14

04 May '14

Hello! I have a record like this: data A = { _bs :: [B]} funcA :: State A () funcA = bs ??? funcB funcB :: State B () funcB = ... What lens operator should I use instead of ???, to update all my Bs? Cheers, Corentin

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Experimenting a new plotting library
by Kai Zhang 04 May '14

04 May '14

Hi cafe, I'm experimenting a new plotting library which makes use of the API of diagrams. I decided to start this work, because: 1. There is few plotting library written in pure Haskell 2. Haskell-chart, one of the most featured library, is hard to extend and there is no straightforward way to compose or modify the plots generated by this library. I had some ideas for the new library. You can get some feeling from here: https://github.com/kaizhang/haskell-plot I'm still relatively new to haskell and don't have much experience in making plots either. Hopefully I can get some suggestions from you guys and improve my programming skills through this process.

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[ANN] codex 0.0.2 - generate tags file from dependencies
by Alois Cochard 04 May '14

04 May '14

Hi, Just to let you know that I released a new version of 'codex' (a tool which allow to generate a tags[1] file for a given cabal project using the sources of all the dependencies of that project). The main new feature is the support of "workspace resolution", which basically mean that if you have the following projects: ~/projects/foo ~/projects/bar Where 'foo' have a dependency on 'bar'... when you run `codex update` in 'foo' directory it will generate tags using the sources available in the sibling directory 'bar' instead of taking it from hackage (as long as versions match). It's specially useful when working on multiple modules, kudos to Edward Kmett for the original idea. [1]Those tags file basically contain references to functions/types definition in source code and allow "jump to definition" like functionality in text editors. source: http://github.com/aloiscochard/codex hackage: http://hackage.haskell.org/package/codex -- *Alois Cochard* http://twitter.com/aloiscochard http://github.com/aloiscochard

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cabal repl fails with GHC 7.8.2
by Omari Norman 04 May '14

04 May '14

I have a package for which "cabal repl" works fine with cabal version 1.20 and GHC 7.6.3. The package has a lot of FFI bindings and uses hsc2hs, so getting a REPL without "cabal repl" is a pain. The package also comes with the C sources that get linked in. But with GHC 7.8.2, "cabal repl" fails with: Loading object (static) dist/build/decnumber/src/decDouble.o ... /usr/bin/ld: dist/build/decnumber/src/decDouble.o: relocation R_X86_64_32S against `DPD2BIN' can not be used when making a shared object; recompile with -fPIC Any idea on how to fix this? "cabal build" and "cabal install" work fine and I can even build and execute a test binary against the library. It seems the problem is just with "cabal repl". Thanks. Omari

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