Wednesday, December 10, 2014

Using Ansi console for nicer console output in EclipseFP

A little tip from the trenches (-:. I use the Ansi Console plugin in EclipseFP to be able to see a nice color output from my Haskell executable runs.

For example, the Tasty example:

Works also for Yesod applications, etc.

Note that some support for Tasty is being added in EclipseFP 2.6.3, to at least provide some templates for the cabal test-suite section and test modules. I'm not too sure if it's worth to develop a runner for it, since contrary to HTF we won't have a link to the source, so the standard output is probably nice enough.

Happy Haskell Hacking!

Wednesday, December 03, 2014

Circling through ideas

I can't make my mind up about what to do in my free time (I have some, yes yes). I keep circling between the same ideas, thinking "that would be good", then jumping to the next one.

  • Keep on working on EclipseFP and other Haskell IDE related ideas. I would like for example to unify the storage of metadata between buildwrapper, scion-browser and eclipsefp, to have one database to would keep library information (definitions, documentations) like scion-browser, AST with types like buildwrapper, usage references like the usage DB in EclipseFP. It could be interesting to try to use that database to drive an IDE and have a clear repository of metadata. But then I'm tired of working on my own on EclipseFP, and when I see that Leksah really has also one active maintainer, I think people are really not interested in advancing Haskell IDEs, they must be happy with Emacs/vi and ghc-mod at a push, so why bother?
  • Then I think working on games is fun! I had fun writing Mazes of Monad, and other little games, and I do enjoy playing role playing or adventure games (I can really recommend the last one I've completed, the Longest Journey), so maybe writing a game the reactive way or even for Android like the guys at Keera Studios do would be a good use of my time. Then I remember I'm a programmer that sucks at graphics design and would probably suck as much at game design.
  • Games are too trivial, let's do something that will change the world, like work on AI! A few books I've read like Kurzweil's and Hawkins' have been truly inspirational, so maybe I could write some HMM neural temporal gizmo that would become sentient over night!! Then I wake up. People smarter than me and with more time than me are already working on that, so I would not contribute anything anyway. Why don't I help these people by providing a better programming experience, for example a Haskell IDE? Back to idea 1!
Ah well, I'll go back to browsing Reddit!

Sunday, November 23, 2014

EclipseFP 2.6.2 released!

I've just released EclipseFP 2.6.2. This is mainly a bug fixing release with a better handling of cabal sandboxes and related functionality. It wraps also an important change in scion-browser, which should now mean that Hoogle uses all the packages present in your sandbox, so should give better results.

Browse the release notes!

Install by pointing your eclipse to

This release is brought to you by me, myself and I. I would love to see more people contribute, even if only to install the development versions to provide some testing before the release, or write some documentation. There's work that can be done on the Haskell side, on the Java side, etc. Contact me if you're not sure, or send me pull requests! The code is at and

Happy Haskell Hacking!!

Friday, September 19, 2014

A new Haskell IDE!

Well, that title is click-bait. It's only a proof of concept, so far (-:, sorry!

I wanted to play with Threepenny-GUI since it allowed to do UI the FRP way, without having the troubles of getting a proper UI library to work. And I was going through a period of frustration with EclipseFP, so I thought about something else for a while... It's got the romantic name of HWIDE!

So in fact, this is a very simple integration of CodeMirror and Threepenny-GUI, to be able to edit Haskell sources inside your browser. When you save your buffer, the data is written to disk, and if a cabal file could be found for that source file, a cabal build (in a sandbox) is attempted (with a configure if needed). The output is then parsed by code ripped off BuildWrapper, and the errors/warnings are displayed, so you can click on them and see the offending line in the code.

That's all, really, and even that is not 100% perfect, but it's a start. I could get to play a bit with Events and Behaviors, develop some little widgets. If some FRP experts want to have a look at the code and offer some advice, I'd be all ears!

I probably won't have much time to turn this into the next generation Haskell IDE, but please fork and hack to your heart's content! The repository is at

Happy Haskell Hacking!

Thursday, September 18, 2014

Learning Scala via unit tests

Last month I followed a big data training session, and we used Scala to write algorithms for Spark. I had looked at Scala some years ago but I think at the time the Eclipse support wasn't very good (the pot calling the kettle black, eh?), and it piqued my curiosity again. So I started looking at tutorials, and found Scala Labs. The idea is interesting: you get a project with sources and tests, and you need to make all the tests pass. The source code for both the code to change and the unit tests is heavily documented, and guides you through the language nicely. And seeing the green ticks appear always triggers the proper reward areas of my brain (-:

I had a little issue getting the code to compile using Eclipse, since there's a sbt-launch-0.13.0.jar library at the root of the project, and Eclipse used that as the top library, and it had a weird version of the List class, that wasn't genericized! I removed that jar from the class path and everything worked fine.

I'm not aware of a similar tutorial for Haskell, but that would be a good idea!

Monday, August 18, 2014

Fame at last!

I was reading the book "Haskell Data Analysis Cookbook" when suddenly, my name pops up! Funny to see a link to a 7 year old blog entry, who knew I would go down in history for a few line of codes for a perceptron? It's deep in Chapter 7, for those interested. Maybe this is a sign that I should abandon everything else and spend my time on AI, since it's obviously where fame and riches abound! Right...

Tuesday, July 22, 2014

EclipseFP 2.6.1 released!

I've just released EclipseFP 2.6.1. EclipseFP is a set of Eclipse plugins for Haskell development. This is a bug fixing release, mainly for GHC 7.8 support.

Release notes can be found here.

As usual, download from

Happy Haskell Hacking!

Sunday, July 20, 2014

BuildWrapper/EclipseFP and GHC 7.8

I've been working on some issues related to GHC 7.8 in BuildWrapper and EclipseFP. On the EclipseFP side, mainly the quickfixes are affected, because EclipseFP parses the GHC error messages to offer them, and the quotes characters have changed in the GHC 7.8 messages.

On the BuildWrapper side, things are more complex. Adapting to API changes wasn't a big deal, but it seems that GHC bugs involving the GHC API, static linking and other unknowns cause some things to break. The solution I've found was to build BuildWrapper with the -dynamic flag. But I couldn't upload this to hackage because Cabal thinks that -dynamic is a debug flag (it starts with d). I've sent a bug fix to Cabal, so in the next release that'll be fixed. So if you're using GHC 7.8 and BuildWrapper, you may want to rebuild the executable with -dynamic (uncomment the relevant line in the cabal file).

Note: BuildWrapper comes with a comprehensive test suite (90 tests covering all aspects). So you can always build the tests and run them to ensure everyting is OK on your system.

Happy Haskell Hacking!

Saturday, June 28, 2014

EclipseFP reaches 100 stars!

This week, the EclipseFP github project reached a hundred stars! Thanks to all users and contributors!! I know still a lot of work is needed to make EclipseFP even better (and faster (-:), so please do not hesitate to participate, on the Eclipse side, on the Haskell side, or on the documentation!

Happy Haskell Hacking!

Tuesday, June 10, 2014

EclipseFP 2.6.0 released!

It's my pleasure to announce the release of EclipseFP 2.6.0. EclipseFP is a set of Eclipse plugins for Haskell development.
The full release notes can be found here. Of particular interest is :

  • Support for cabal 1.18 sandboxes
  • Worksheet for live programming (like GHCi expressions but automatically refreshed on save)
As usual, just install by pointing your Eclipse to

Happy Haskell Hacking!

Tuesday, March 11, 2014

Reflecting on Ubuntu

It's been a while now since I moved to Ubuntu as my Haskell development OS. On the whole working in Ubuntu is a pleasant experience. I adapted easily to the UI, the support groups have loads of answers when I have an issue, and things usually install well, be it Haskell libraries or additional tools. I like that 99% of the time the upgrades do not require a restart. I have a few gripes, though.

  • Eclipse is not always stable and crashes from time to time (a couple of times a week), say. I haven't found any fix for that yet. It seems to be a UI library issue, maybe something to do with SWT. 
  • Maybe it's linked, but I've had some cases where Eclipse seemed to starve the machine of resources, and it was a huge pain to kill it. In Windows I go Ctrl-Alt-Del and kill the process via the task manager, and that's not an issue. On Ubuntu going Ctrl-Alt-F1 to go to another session, login, find the process and kill it tooks ages. I tried to change to setting to forbid an application to take to much resources but I don't think it helped. There's maybe another way to kill a misbehaving application that I'd love to know...
  • There are still some rough edges for things that should be simple. I can't get my printer to work (a run of the mill Canon printer), and there's a limit to the number of hours I'm willing to spend on getting something stupid like that to work. The other day RhythmBox (the software that apparently tries to play my CDs) crashed repeatedly after the first song on a CD that plays fine on Windows (maybe RhythmBox doesn't like Michael Schenker?). Seriously? Playing a CD is too hard?
So in the end, after hearing for years that Windows was not a great OS, I don't find Ubuntu that more stable or solid. I love not to be on a third-grade OS for Haskell libraries, don't get me wrong, so I'll stick with it, and hopefully the issues will go away!

Friday, February 14, 2014

Hidden Markov Models for Natural Language Tagging, in Haskell

I became intrigued in Hidden Markov Models after reading Kurzweil, who claims they can be used to model the thinking process in the brain. There is much debate about that, but these are interesting AI structures. This page I think has a good introduction.

I was working though the (partial) online book on Natural Language Processing with Haskell, and thought of combining the two. I used Mike Izbicki's hmm library for a one order Hidden Markov Model implementation. Once I initialized the model properly using the training data, I got around 91% accuracy on tagging, which is on par with the rules based approach presented in the nlpwp book.

I used the strategy outline in this paper to deal with unknown words (words in the test set not met in the training set): replace these words with a token that is also used for low frequency words in the training set. So far I've used only one token but I suppose being a bit more fined grained (to distinguish words starting with a capital letter, currency amounts, numbers) will improve results.

Performance is not very good even with some parallelism, so I think I need to spend more time on it, but it's definitely encouraging. It'll be a little bit of time till I have a thinking brain, though, but there is hope!

Sunday, February 02, 2014

Beginning Haskell: the Book!

It's my pleasure to relay the news of the publication of a new Haskell book, Beginning Haskell. It's written by one of EclipseFP contributors, Alejandro, and I've had the pleasure to be a technical reviewer of the book. I learned a lot, so I can heartily recommend it! It takes the reader from the very basics of functional programming to some intermediate and advanced Haskell techniques. Alejandro of course talks about it better than me.

Happy Haskell Reading! Thanks Alejandro for the great work!

Friday, January 24, 2014

Haskell Worksheet in EclipseFP 2.6

A sneak preview of the worksheet functionality in the upcoming EclipseFP release. I have a Haskell module with a few functions, and the worksheet displays some results using different rendering modes:

  • Simple text: shows the result of the expression as GHCi would
  • HTML/SVG: renders HTML markup and SVG images in a SWT Browser element. In the screenshot there's Blaze HTML and Diagrams SVG
  • JSON: display JSON objects and arrays in a tree
We use BuildWrapper and the GHC API to execute the expressions every time the file is saved. The expressions are persistent and hence survive restarting Eclipse.

I don't know when EclipseFP 2.6 will be released, but you can of course get the current code from github.

Thursday, January 09, 2014

Cabal sandbox support in EclipseFP 2.6

I seem to have managed to free myself a bit of time, which means I can work a bit on EclipseFP 2.6.  I've added support for cabal sandboxes, so you'll be able to use sandboxing with cabal 1.18 in pretty much the same way cabal-dev was supported. You can have a per project or per workspace sandbox, and the fact that add-source is dynamic simplifies the internal code somehow. Cabal-dev is still supported.

A nice side effect of supporting Cabal 1.18 (thanks again to dynamic-cabal) is that we can use a sandbox to install the executables we need, like buildwrapper and scion-browser. Up to now, if you hadn't installed them, you'd get a dialog box asking you if you wanted to. Users have complained that this was an unnecessary step, but I didn't want to install executables with many dependencies into the user's package database without a notice. Now, executables get installed into a specific sandbox, so the install may be a bit longer if you already had some dependencies, but we don't mess up anything on your system.
The only issue is that inside a cabal sandbox, all packages need to be coherent: you cannot have two different versions of the same library. This shouldn't normally be an issue, but it is at the moment, because we try to install HLint and SourceGraph, that both require a different version of haskell-src-exts. I have sent a patch to Ivan Lazar Miljenovic so that SourceGraph can support the latest version of haskell-src-exts so hopefully this will be sorted by the time EclipseFP 2.6 hit the metaphorical shelves.

So hopefully EclipseFP 2.6 will be easier to install and will take advantage of the latest Cabal functionality!