Friday, December 30, 2011

EclipseFP and "the future of programming"

Paul Chiusano's essay "The Future Of Programming" has sparkled a lot of debate, for example on Reddit. His points on IDEs remind me somewhat on what Luke Palmer has to say on them. And he's strongly in favor of lazy, statically-typed, functional languages.

I suddenly find myself in a strange (good?) position: as a maintainer of an IDE (ok, plugins) for Haskell, I can somehow participate towards fulfilling that dream. I know, I know, we're far from it, and EclipseFP has not yet reached the ease of use and power of the JDT in Eclipse. But maybe we can achieve success by doing things differently, not by trying to mimic what's already there and anyway applies to a different language.

We've already started to take some steps in the right direction: for example, Alejandro is working on a version of scion-browser that stores its data in a database. It's not such a big leap to envision that a lot of information about the developer's projects and modules could be kept in that database, to give accurate and fast searching and refactoring operations. We'll also need to think about providing an editor that is a lot more structured than the standard text-with-foldable-sections editor we have now, but it's not clear now if

  • the benefits of a structured editor justify developing an interface programmers are not used to
  • people would take the plunge even if we could prove tangible benefits

I can already see a clear advantage in having an editor that always force you to have valid code: EclipseFP loses a lot of functionality (thingAtPoint for example doesn't work) if the module you're working on has errors, because the GHC API can provide a lot more info once the module can be analysed correctly. With things like "undefined" and type-directed autocomplete support we could have modules that are always correct. I'm not sure myself that having a compiling module with loads of undefined that fails miserably at run-time is such a great proposition, but hey... In Java, Eclipse let you run a file with errors and only throws a run-time error when you access the incorrect code.

So we'll have to overcome usability and performance issues, deal with GHC limitations and programmers' expectations, but we're in the position to at least try, and see if we can move forward a little bit!

Wednesday, December 28, 2011

Lego Mindstorms and Haskell?

Santa brought me a Lego Mindstorms kit! Suddenly the time I'm going to have available for EclipseFP is greatly reduced (I joke). I'm having fun building my first little models and fiddling with the graphical interface for programming the little beasts, but I was wondering if I could use Haskell to control the robots. Things look bleak:
- the NXT library on Hackage looks good, but requires unix... Maybe getting it to work on Windows would be easy, but I wonder...
- the fantom development kit (fantom is the low level communication API for Mindstorms, if I understand correctly) comes with a Windows version that will only work with Visual C++. It uses C++ lib and dll files whose name mangling is not compatible with MinGW.

So as a Windows and MinGW user, I'm in a bit of a ditch. I'm wondering now about the Urbi platform, that seems to be open source and to have a module for Mindstorms. It seems to provide a C++, Java and scripting interfaces, so it may be possible to get a Haskell wrapper on top of it. I wonder has anybody worked on Haskell bindings for Urbi? Might be interesting...

Monday, December 26, 2011

Buildwrapper 0.2.2 released

Hello all, I've just released a new version of buildwrapper, which is one of the backend Haskell executables used in EclipseFP. This is a bug fixing release, addressing some of the issues reported by people. Just install the new version via cabal install or via the EclipseFP cabal packages views.
There is ongoing work on EclipseFP and scion-browser, so a new version of both should hit the shelves pretty soon, in a matter of weeks!

Happy Haskell Hacking!

Saturday, November 12, 2011

EclipseFP helper executables for Windows

Since people had sometimes problems building Haskell executables we use in EclipseFP, I thought I'd help by putting versions of the current Windows executables on sourceforge. So in you run Windows and have trouble building scion-browser or buildwrapper, you can grab them from here.

I know this isn't really in the spirit of "build from sources so you can check them yaddi yadda", but since even Cabal does it...

As usual, use at your own risk, etc.

Happy Haskell Hacking!

Friday, November 11, 2011

EclipseFP 2.2.0 released!

I'm glad to announce that EclipseFP 2.2.0 has been released. EclipseFP is a set of Eclipse plugins for Haskell development.

The minor version increase is justified by the replacement of the Scion library for the backend by the BuildWrapper executable. I appreciate that lots of work went and is still going into Scion, but I decided that building my own Haskell backend was better for EclipseFP. It calls cabal directly for building, which allows EclipseFP to support things like new style component dependencies (the executable in a project depends on its own library), c files (now my HJVM project, which call Java from Haskell can build, and even report errors in the C code), etc. Note the the haskell code is not bundled with EclipseFP anymore but gets downloaded and installed from Hackage.

This version also comes with a new view, allowing the installation of cabal packages from Hackage. There are also bug fixes and small enhancements all round.

To install, just use the built-in Eclipse install/update functionality. The update site URL is The release notes can be found here.

Happy Haskell Hacking with EclipseFP!

Thursday, October 20, 2011

GUI Testing using OCR: project Sikuli

I had a great idea this morning... and then realized that there was an open source project already doing it.
I thought: instead of using specific testing frameworks for each UI technology I have (a tool for the web, a tool for SWT UIs, etc) what about a tool that could recognize the text on screen and click or type in the proper places. The same technology for everything type of UI, and something that doesn't rely on pixel perfect positioning to work! Turns out (surprise!) I'm not the first one that had the idea, and looking around I stumbled on Project Sikuli. This looks great: it uses images to find "interesting" parts of your UI and there's also support for text recognition. So potentially you could say "click on the button that says 'Submit'"! It integrates with Java code so you can easily have JUnit tests using it.
Unfortunately, for my own purposes I couldn't get very far easily because of lack of support for transparent images (or, more precisely, it takes into account transparent areas for images, so it doesn't recognize an image if the background changes, which happens if your desktop theme changes, if you use the same icon in different contexts in your UI, etc). But it still looks like a promising tool!

Thursday, October 13, 2011

Manage Cabal packages from inside EclipseFP

I'm thinking the new version of EclipseFP will not bundle the Haskell code we use, but will download it from Hackage, which would make sense: we would be able to update the Haskell side without requiring a EclipseFP upgrade, and vice versa. I would expect Haskell developers would be quite used to install packages from Hackage using cabal install. However, let's try to minimize the number of things that a user would need to go outside of EclipseFP to do on a normal Haskell project. So I've added another view:

This view lets you see the list of packages you've installed, with their version, or the full list from Hackage, that you can filter by typing the prefix of the name you're looking for. From there you can install the packages as either Global or User, see the package information, or click on the "More Information" link to open the Hackage page directly.
You can also update the list. This GUI is only a wrapper above the cabal list and cabal info commands.
Hopefully this will be useful to people! Should I add a text field somewhere to be able to specify more options to cabal install, or is that overkill for a GUI?

Friday, October 07, 2011

New backend for EclipseFP

A while ago I was wondering how I could enhance EclipseFP, regarding things like memory usage, support for multi components projects, etc. I now have a working version for adventurous testers!

The main thing is the removal of Scion. EclipseFP now uses another backend component called "buildwrapper". There is no server, buildwrapper is only an executable that can be launched with flags, and writes a JSON result on the standard output. This means no more huge memory usage, and less synchronization headaches.

Buildwrapper uses a copy of the project inside a hidden folder. This means that when we want to get say build errors on a dirty editor content, we can write the dirty content to the file inside the hidden folder, and launch a build process on these files, thus avoiding the limitations that the GHC API has on building from a StringBuffer (doesn't work for files requiring preprocessing, etc).

We only use the GHC API to get the types of things in a source file, but we use Cabal to build the project. Buildwrapper actually launches the cabal executable and parses the results. I know, sounds crude compare to an API only approach, but I have the feeling it just works better. Basically the IDE will now behave a lot close to what you get if you were building your project from the command line. And then you get additional goodies, like multi component support (so you can have the executable of your project reference the library in the same project, and it works!).

Buildwrapper uses haskell-src-exts for outline. I've actually seen cases where it needed language pragmas to parse correctly that GHC didn't need, but such is life.

Performance seems to be quite good, except for things that use the GHC API, where there's a little lag. Hopefully the fact that we don't use gigs of memory any more will make up for it.
I'm also thinking about distribution. EclipseFP came with Scion and Scion-browser bundled, if only because we used a different version of scion than the one on Hackage. I think that moving forward we'll rely on cabal install and Haskage. I'm going to add a simple interface to run cabal install inside EclipseFP, so you shouldn't have to go outside to install a package. So the EclipseFP preferences will just ask the user for the path to the buildwrapper and scion-browser executables, with an option to install them from hackage.

If people want to start testing, just go on github, and grab the BuildWrapper repository (main branch) and the EclipseFP project (buildwrapper branch). For the moment, BuildWrapper probably only builds on GHC 7.0. Once I have the feeling it's robust enough and there's no big flaw in the new architecture, I can work on enhancing portability.

Friday, September 02, 2011

EclipseFP 2.1.0 released!

It's been a little while, but finally a new version of EclipseFP has been released! This version is mainly the work of Alejandro Serrano, who has worked on EclipseFP (and the underlying utilities) during his GSoC project. There are lots of new features in that version, mainly :

  • A package/module browser
  • Hoogle integration
  • Support for running tests
  • HLint warnings
  • Support for running executables and get profiling graphs
  • SourceGraph generation
  • Better auto completion information

Lots, I'm telling you. There are also fixes and internal enhancements that hopefully should make your life easier.
You can just run the update from your Eclipse IDE. You can find the full release notes there.
Note that Alejandro has also created a new web site for EclipseFP, that you can find there. Alejandro, big thanks for your hard work and your dedication!

Any feedback is welcome, and of course bug reports and requests for enhancements!

Happy Haskell hacking in Eclipse!

Wednesday, August 31, 2011

Hoogle Command Line on Windows

The new upcoming version of EclipseFP will feature Hoogle integration, thanks to the work of Alejandro Serrano, so I was doing some testing on one of my Windows machine (yes, I'm a Haskell hacker and a Windows user, so what?)... No real problem using Hoogle via the command line, but since it does require some other things to be installed, I though I'd post them there for reference.

Unlike Cabal, Hoogle uses external tools for some of its operations. These tools are I'd say part of any self-respecting Unix distribution, but not of Windows. So you'll need:

At time of writing, the download page is

At time of writing, the download page is

At time of writing, the download page is

Install everything in the same directory and put the bin subdirectory in your PATH. hoogle data should run fine.

Note also that since it's using wget, if you have an HTTP proxy you need to configure wget to use it (Cabal uses the internet explorer connection settings and finds the proxy settings from that). The files is etc\wgetrc in the directory you installed wget, find the http_proxy entry and adapt to your settings.

Friday, June 24, 2011

EclipseFP: the way forward??

This is not the usual "hey I managed to get some code to work, check it out" blog post. Bear with me as I'm just thinking out loud. This is about EclipseFP and how we can move it forwards.

At the moment EclipseFP works pretty well for simple, smallish Haskell projects. People have noted some performance issues on large projects, and part of it is the huge memory footprint of GHC when used through its API. After a couple of hours of working on a yesod project (so we're talking quasi quotation, template haskell, etc), the scion server takes 1Gb of memory... Restarting brings it back to reasonable levels, which seems to point to memory leaks in the GHC API.
Maybe more critically, people are now asking for features that get increasingly harder to implement using Scion:
- static GHC flags like -threaded (Nominolo's working on a version of Scion that could handle these)
- C or HSC sources (or other kind of stuff requiring a preprocessor)
- Having executables or test suites referencing the library component directly in the Cabal file

The main thing with these is that Cabal handles them fine, so basically typing cabal build at the command prompt solves these issues, which undermines the usefulness of having an IDE in the first place... But they require more than just calling the GHC API: building and linking a library in-place, calling a c compiler, hsc2hs, etc...
Of course Cabal publishes an API. So for example the code used by Cabal to build an in-place version of the library I could access, in theory, from Scion. But then Cabal calls the ghc executable, so the Cabal API gives me no easy way to get back errors from GHC, etc...

What does accessing the GHC API gives us? An AST, that can be generated from an unsaved file (so you don't need to save your haskell source file to see your errors, our up to date outline, etc). All the rest (syntax highlighting, jump to definition, etc) could probably be done from the AST.

So I'm wondering now if scrapping scion totally would not be a good idea. A rough outline of how things could work would be:
- create a temp folder in which we will work, copy in it all the project files (sources, etc)
- use cabal to build in that folder
- parse cabal output to get errors and their location
- unsaved files in the EclipseFP editor could have their unsaved contents copied into that folder (that folder represent the current state of the project, which may not be what is really saved on disk)
- have only a simple Haskell executable that given a module file, loads it using all the built files in the temp folder, and return the AST in some easy to parse format. Firing and getting the result would ensure GHC cannot grab loads of memory and not release it
- the IDE code then gets the AST and does all it needs to it
- the AST could even be saved in that temp folder in some format, so that the Java code would only request it when the original file is more recent, which would allow easy parsing of dependent modules AST (for example to retrieve all the symbols exported, etc)

There are a lot of ugly bits in there, maybe, but that would solve my problems... I suppose all of that could be written in Haskell and we could keep a similar enough API to scion, so that the Java code wouldn't need change too much...

For the moment I'm not going to reach into things anyway, but if anybody has some feedback, I'll gladly take any opinion on board!

Sunday, May 22, 2011

Haskell + FFI + Java + SWT: crazy, maybe, but working!

A few years ago I noted that being able to mix Haskell code and a Java GUI might be a good idea, since Java UIs have matured enormously, and Haskell UI library are still struggling to gain wide adoption, a recent thread on cafe being proof. SWT bindings were mentioned, so I had a look at both the Java and the C SWT code, for windows. Two immediate things sprang to view:
1. The SWT C library is using JNI, duh. It relies on JNI for some operations so you can't just use the SWT.dll in your haskell code that easily
2. The SWT C bindings are very low level, and there is a wealth of Java code on top of that to provide a lot ow glue and boilerplate code for all kind of widgets, and it would be long and painful to rewrite it all in Haskell.

My Java to Haskell code converter only being a dream at the moment (one day...), the next reasonable (ahem) option was then obvious: start a few blown JVM from Haskell and use it to drive SWT classes.
I'm a Java expert, I can say, and my Haskell is slowly coming on, but the glue in between has to be C, so it wasn't a smooth ride, but I finally got it working! So what's happening is this:
- The Haskell applications starts as they all do, in a main :: IO() function
- Haskell invokes some C code that starts a new JVM, passing it a classpath. The C code acts then as a facade hiding some of the intricacies of accessing the JVM
- Haskell uses the foreign C functions to create ands manipulate the SWT Java objects
- I even got callbacks working, meaning you can register a Haskell listener on a SWT button, and hence have Haskell code calculate the results of that button click.

And I have proof! Here's a simple SWT Shell with one button:
When you click the button:

And the handler for the button click is written in Haskell (I have a MVar called count for the number of times the user clicked):
    modifyMVar count (\c->do
        let nc=c+1
        let s=if nc==1 then "once." else ((show nc)++ " times.")
        text3<-toJString ("Clicked "++s)
        voidMethod button "setText" "(Ljava/lang/String;)V" [JObj text3]

You can see here the invocation of the setText method of the SWT Button, which for the moment requires knowing the exact JNI signature, and the translation from Haskell strings to Java strings.

Of course, there is still loads to do. I probably need to automatically generate bindings to the Java objects to simplify greatly their manipulation, wrap stateful operations in a monad, etc. But this may open a new way for Haskell GUI. Or it may just be a crazy idea that has already taught me a lot about FFI and JNI...

Monday, April 18, 2011

Pirates 0.2: fixes and a chat interface

I released a little update to my Pirates Yesod/Canvas game. Nothing too dramatic, but the new version, still at boasts:

  • Fixes in the collision detection code
  • A chat interface, so you can talk to the other ship you're fighting with. Stock up on pirates insults!
  • Fixes in handling of games when a ship leaves the game before it's finished
As I said, nothing too fancy, but I find that polishing off bugs and adding unplanned features is often a good exercise, especially for personal projects where the temptation is great to just move to something else when it kinda works. The chat interface was interesting: the server side code was done in a few minutes, using the same event system as the rest, but I struggled longer with the HTML to get the right positions for everything, as usual... Now it's on the right hand side, outside of the canvas area, which makes the full game area much bigger than the original 800x600, but I don't think I get a lot of mobile users anyways (-;.

I could probably make the game more appealing long term by having a bigger area where more than 2 ships could battle, and have more of a RPG feel to it (maybe be able to log in and out so you keep your ship, be able to repair it in harbours, etc...). I'll see what I have time to do. Any suggestions welcome!

Friday, April 08, 2011

Pirates!! A multi-player browser game with Yesod and Canvas

I can finally open to the public a little game I've made! You can now go to and play!
The game is simple: you're sailing a pirate ship, and you have to sink your opponent. You can use cannons, ram the other ship, board it with your blood-thirsty crew. Your speed depends of course on the direction and strength of the wind. You can play alone versus a very dumb AI (mainly to get the hang of the controls), against a friend in a private game, or against any dog on the internet. 
The technology stack is as follows:

  • Hosting is on a free Amazon EC2 instance. Performance is probably not going to be great, but should be sufficient I hope for the traffic I'll be getting!
  • Server side is Yesod 0.7. Coming from the Java/JSP/Struts world it was such a pleasure to work in Haskell, with type safe templates. I have no web server, just warp, since there are very few static files (a few sprites and the tile image).
  • Client side uses Canvas with a sprinkling of JQuery.

As you can see, no database. Information about current games is purely in memory, and I don't keep any long term information about players. I suppose that allowing players to log in with their Google or Facebook id, and keep statistics on their battles would be good, but I'm not sure this little game will get enough traction to warrant it, really... 
The AI also is not great shake, there are only two bots: The Sitting Duck turns to face the wind and stays there. The Drunken Sailor just goes randomly through all possible actions. But hey, it's a multi-player game!
I'm not too sure if I chose the best route for concurrency. I use MVars and modifyMVar.
In fact the more difficult bit was to design the control. I didn't want to a do a full 3D environment, and opted for a top view, but the velocity of the ships was essential, and so providing just direction keys as in more static games wouldn't have worked. Hopefully the way the control works, being disposed on a copy of the boat icon at the top of screen, that turns when you boat turns, will work well. The icons are probably a bit small, it's fine for a mouse but I don't think it could work on a touch screen, unless you have tiny fingers.

A little bit of personal info: inspiration from this game comes from the French magazine "Jeux et Strat├ęgies", that my dad used to get when I was young, and that got me into games. We have still kept all the issues, and issue 22 from August 1983 describes a simple ship battle game, rules written by Michel Brassinne (French warning!). Thanks!

Still it was fun to do!! Hope you enjoy playing it a little!

Friday, April 01, 2011

Install GHC7 and Yesod on Amazon Linux

I've been working lately on a multi-player web game, to actually get to know HTML Canvas (on the client) and Yesod (on the server) properly. I have a first fully functional version of the game, so now is the time to think about hosting. Michael initiated a discussion about it, and in the meantime I decided to investigate Amazon since they offer free instances now on EC2.
The free AMIs (images) come with a version of Linux specific to Amazon, but apparently binary compatible with CentOS, on which GHC and the Haskell Platform have been reported to successfully build.
These are the steps I followed to get everything working, hopefully they can be useful to somebody else. So as per the Amazon Getting Started guide, you connect to your instance with the ec2-user.
First we install through the package manager some useful packages:

sudo yum install make
sudo yum install gcc
sudo yum install zlib-devel
sudo yum install glut
sudo yum install glut-devel

I didn't find gmp, so I downloaded and installed in the default location:

curl -O
tar -xjvf gmp-4.3.2.tar.bz2
cd gmp-4.3.2
sudo make install

But afterwards I had issues building some Haskell packages because it didn't like the default install folder of /usr/local/lib, it preferred /usr/lib, so I did:
sudo cp /usr/local/lib/libgmp.* /usr/lib/
But I suppose ./configure --prefix=/usr/lib/ would be the preferred way to do that.

Libbsd is also required otherwise unix-compat fails:

curl -O
tar -xzvf libbsd-0.2.0.tar.gz
cd libbsd-0.2.0
sudo make install

Then for GHC, I just downloaded the generic binary and installed that. I decided to install Haskell under my home folder.

curl -O
tar -xjvf ghc-7.0.2-i386-unknown-linux.tar.bz2
cd ghc-7.0.2
./configure --prefix=/home/ec2-user/haskell
make install

Make sure we know how to find it:
export PATH=$PATH:/home/ec2-user/haskell/bin

Then get the Haskell Platform source and build that, since there is no binary (yet) for our platform:

curl -O
tar -xzvf haskell-platform-2011.2.0.0.tar.gz
cd haskell-platform-2011.2.0.0
./configure --prefix=/home/ec2-user/haskell
make install

Once you're there, it's back to familiar ground:

cabal update
cabal install yesod

And there we are!! My deployment platform is ready!

Monday, March 21, 2011

EclipseFP 2.0.4 released: supports GHC 7!

Hello, the demand was HUGE (well, everything is relative :-)) for a version of EclipseFP that could build and run on GHC7. Since the 2.0.3 release there is now a Haskell Platform release that contains GHC7, so we had no excuse... And there it is! Thanks have to go mainly to Alejandro Serrano, for getting Scion to compile with GHC7 and to Thomas Schilling and Matti Niemenmaa, who upgraded their libraries for GHC7.

So what we have is a scion backend that should build both with 6.12 and 7.0, and hopefully work the same on both. We now support test-suite sections in Cabal files, with limited support for running test suites (running just cabal test with no options).

On my To Do list are full support for test-suites (having full launch configurations for Cabal defined tests) and HLint integration. But I'd also like to work on my own project, so don't expect that a release every two weeks is going to be our normal cruising speed.

As usual, just install from the Eclipse update site:, and bug reports or feature requests should go to the SourceForge forum or the development mailing list.

Happy Haskell Hacking!

Monday, March 07, 2011

EclipseFP 2.0.3 released

It's my pleasure to release EclipseFP version 2.0.3. EclipseFP is a set of Eclipse plugins for Haskell development. Scooter and I have tried to add a few features and hopefully to fix the bugs that were reported by users.

Main things in this version are code completion templates, which enables you to code even quicker!! We also enhanced the Cabal support (you can now set Cabal flags from the project properties, run Cabal install on the project) and simplified the installation (more settings are auto detected).

EclipseFP is alive and well (I use it for all my Haskell work) so please send us all your feedback, bug reports, feature requests!

Use the standard Eclipse Updates Site  or download files. Enjoy!

Friday, January 21, 2011

Evolving a computer with TECS and Genprog

I've started reading The Elements of Computer Systems since it was recommended on Reddit and it's a great read. After the section on boolean gates I decided to have a quick go at build the gates in Haskell. Just implement Nand with pattern matching, and implement all the other gates just in term of functions calls to previously defined gates. The book mentioned "think positive" about implementing Not, so I just T as the second parameter, did't think more about it, even though I wasn't sure having a constant value was OK.

Then I moved on to the other gates. It was interesting to think about boolean logic without Or, for example, after years of only reasoning in terms of And Or and Not. But at some stage I thought "why am I doing this by hand?". I remembered a thread about a new genetic programming library on an Haskell group. Surely generating the gates would be simple enough?
So I got genprog from hackage, and adapted the example for my needs. I started with a very simple system to determine the implementation of Not:

And of course, the result came quickly enough: not a=nand(a,a). No need for a Const at all! Evolution has beaten me! (OK, I'm only a not-so-intelligent designer, I suppose...)
Now, I'm going to see if this approach can take me all the way to the arithmetic unit...