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aeson-utils: aeson-0.9 compatibility package
by Adam Bergmark 26 May '15

26 May '15

Hi folks, aeson-0.9 was released today. It changes the behavior of `decode` and `eitherDecode`: They now both allow atomic values on the top level. Previously the behavior was inconsistent, `encode 1 = "1"` but `decode "1" :: Maybe Int = Nothing`. aeson-utils[1] has the functions `decodeV` and `eitherDecodeV` that work like aeson-0.9's `decode` and `eitherDecode` respectively, also with older aeson versions. If you want to stay backwards compatible without having varying semantics based on dependencies, check it out! [1] http://hackage.haskell.org/package/aeson-utils Regards, Adam

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Any recommendations on how to interact with the running state of a program?
by Anatoly Yakovenko 26 May '15

26 May '15

I am playing around with some deep learning algorithms and I need a way to periodically read the intermediate result and change some of the system variables. Any ideas on how to best approach this problem? I was thinking of something basic, like having the program periodically read and write from some files. Thanks, Anatoly

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New Functional Programming Job Opportunities
by Functional Jobs 26 May '15

26 May '15

Here are some functional programming job opportunities that were posted recently: Clojure/Erlang backend engineer/architect at Zoomo http://functionaljobs.com/jobs/8831-clojure-erlang-backend-engineer-archite… Cheers, Sean Murphy FunctionalJobs.com

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ANN: Leksah 0.15
by Hamish Mackenzie 25 May '15

25 May '15

Hi Everyone, The new leksah package is in Hackage and the installers for Windows and OS X are available for download at: https://github.com/leksah/leksah/wiki/download (remember to choose the one that matches your GHC version) Nw in this release: * Support for GHC 7.10.1. * Uses Gtk+ 3.16 on Windows and OS X. * GtkInspector works on all platforms (Ctrl+Shift+I). * Updated build instructions https://github.com/leksah/leksah (OS X and Windows builds are fairly easy now). * Underlining of doctest failures. * Lots of bug fixes. Things that are new since 0.14.0: * Support for using GHCJS. https://www.youtube.com/watch?v=zQnExdDL63c * GtkInspector https://wiki.gnome.org/Projects/GTK%2B/Inspector. * Web Inspector pane (right click on output pane to bring it up. https://trac.webkit.org/wiki/WebInspector * Cabal commands executed by Leksah show up in the log pane. I remain optimistic about the future of Leksah. GTK+ has improved hugely in the last couple of years. Also WebKitGTK+ and GHCJS mean integrating tools into Leksah will be easier than ever. A great many people contribute (mostly indirectly) to Leksah, it is much appreciated and I hope that number will grow. As always, please help! Hop on #leksah or file and issue at https://github.com/leksah/leksah/issues, even if it is just to vent your displeasure with Leksah (every bug report helps). Here are some fun ideas you might like to try working on if you are looking for a way to contribute to Leksah: * Try using Leksah and fix the thing that annoys you most about it. * Figure out if/how ide-backend can be used in Leksah. * Create an XMonad like manager for <div> based panes. Ideally it would work for both GTK+ and GHCJS. * Migrate existing UI components from Gtk+ to GHCJS. * Anything GHCJS based and then add support in Leksah for it. * GHCJS based scripting (make it work for Leksah like elisp for Emacs). * Improve Yi integration. What we have is unusably incomplete. * Add GHCJS backend for Yi (replacing the Pango one). * Improve JavaScript based editor support (currently only CodeMirror is supported and not very well). * Add support for using SoH and/or FPView within Leksah. If you are interested in any of these please let me know and I will do what I can to help you get started. Hamish PS. I am kind of sad Eclipse FP has stalled for now and I hope it restarts soon. Integrating Haskell into existing IDEs (especially those with large user bases) will help sell Haskell to the world. I wish JP well and I am sure he will find something interesting and challenging to work on next.

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Increasing parallelism in a frequency counter
by Andreas Pauley 25 May '15

25 May '15

Hi everyone, I've started playing with some parallel programming in Haskell, mostly by applying the first few examples from Simon Marlow's book to my own toy problem: https://github.com/apauley/parallel-frequency I'm quite pleased with the speedup I have so far, the fastest parallel implementation is just over twice as fast as its sequential counterpart. But looking at the threadscope images from the generated event logs I can see that there are still significant portions of my program that runs on only one core. Is anyone interested to see if we can increase the parallelism in this frequency counter? Kind regards, Andreas -- https://keybase.io/apauley http://za.linkedin.com/in/apauley http://www.meetup.com/lambda-luminaries http://www.meetup.com/Bitcoins-Baby-Bitcoins GPG Public Key: https://keybase.io/apauley/key.asc

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Fwd: Abandoning String = [Char]?
by David Feuer 25 May '15

25 May '15

Performance will go utterly out the window if you use pattern synonyms and the like to pretend that Text is [Char]. It would probably work fine (great, even) when matching, but code that assumes String=[Char] would be completely killed on the construction side, because building Text by consing, or repeatedly prepending small chunks, is ridiculously inefficient. These are the very things that are *efficient* with [Char], and that people have assumed to be efficient when writing code that uses it. On May 22, 2015 5:58 PM, "Carter Schonwald" <carter.schonwald(a)gmail.com> wrote: > > one direction that this thread has *COMPLETELY* overlooked is the following: > > could we use pattern synonyms or something along those lines to make the migration to Text or the like more seemless?

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Munich Haskell Meeting, 2015-05-25 @ 19:30
by Christian Neukirchen 23 May '15

23 May '15

Dear all, Next week, our monthly Munich Haskell Meeting will take place again on Monday, May 25 at Cafe Puck at 19h30. For details see here: http://www.haskell-munich.de/dates If you plan to join, please add yourself to this dudle so we can reserve enough seats! It is OK to add yourself to the dudle anonymously or pseudonymously. https://dudle.inf.tu-dresden.de/haskell-munich-may-2015/ Everybody is welcome! cu, -- Christian Neukirchen <chneukirchen(a)gmail.com> http://chneukirchen.org

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open gl type conversions
by briand＠aracnet.com 23 May '15

23 May '15

Following code GLFW.setWindowSizeCallback w (Just (\window w h -> do GL.viewport $= (GL.Position 0 0, GL.Size w h) emo1.hs:42:50: Couldn't match type ‘Int’ with ‘Foreign.C.Types.CInt’ Expected type: GLsizei Actual type: Int In the first argument of ‘Size’, namely ‘w’ In the expression: Size w h I can never seem to figure out if i really need to do a type conversion, or just the make the appropriate type declarations. Sometimes it seems to be a combination of both. Part of the complication here is that w and h are, in fact, `Int` because that's there type in the type signature of WindowSizeCallback (Window -> Int -> Int -> IO () ). GL.Size really needs a CInt so it seems like I have to do some sort of explicit conversion, but I can never seem to figure out exactly how to find the necessary function. Humorously i tried putting Int->CInt in hoogle, and the only thing that looked like it might be useful was unsafeCoerce, but I'm pretty sure that's not the right answer. I was wondering if someone could enlighten me on exactly how you can trace out the solution to this sort of problem because it seeems to come up often (see, for example my confusion over FFTW r). Brian

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Abandoning String = [Char]?
by Andrew Gibiansky 23 May '15

23 May '15

Hey all, In the earlier haskell-cafe discussion of IsString, someone mentioned that it would be nice to abandon [Char] as the blessed string type in Haskell. I've thought about this on and off for a while now, and think that the fact that [Char] is the default string type is a really big issue (for example, it gives beginners the idea that Haskell is incredibly slow, because everything that involves string processing is using linked lists). I am not proposing anything, but am curious as to what already has been discussed: 1. Has the possibility of migrating away from [Char] been investigated before? 2. What gains could we see in ease of use, performance, etc, if [Char] was deprecated? 3. What could replace [Char], while retaining the same ease of use for writing string manipulation functions (pattern matching, etc)? 4. Is there any sort of migration path that would make this change feasible in mainline Haskell in the medium term (2-5 years)? Thanks! I would welcome any references or links that my cursory googling has failed to find. -- Andrew

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Installing ghc-mod on Windows
by Anakreontas 23 May '15

23 May '15

I tried to instal ghc-mod on Windows with cabal. Two dependencies fail to compile because of missing native libraries. ansi-terminal requires kernel32 and lifted-base requires inlinable.h. Have you solved a similar problem? In Linux it would be easy to install the native libraries but in Windows I do not know which programs I should install and where to find them.

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