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Ideas for an opensource project

Haskell on Reddit - Sun, 02/15/2015 - 10:05am

We're a bunch of Haskell enthusiasts that get together weekly to talk about and discuss all things Haskell. It's a small group for now. But we anticipate it growing larger in the near future. And as the group becomes bigger, we'll have folks with varying skill levels. Beginner to Advanced.

We would like to get started with some opensource idea. Something that we can implement in Haskell, and learn as we go. Something that would allow us to participate in a coding marathon of a few hours every weekend or so and be able to see some measureable progress. Being able to measure the progress is important so that we can feel motivated to carry on.

So far we've thought about, * a docker web frontend to manipulate containers and visualize connections between containers * a haskell version of "pydoc". basically a documentation server that serves documentation of the packages installed in your sandbox.

There were a few other ideas thrown around. But the ones mentioned above were noteworthy.

What we would like to know is if there is any other idea worth pursuing/considering? Anything, that the haskell community would like, that does not exist at the moment, perhaps!.

submitted by desijays
[link] [16 comments]
Categories: Incoming News

ANN: New Homepage Now Live

haskell-cafe - Sun, 02/15/2015 - 9:50am
I’m pleased to announce that has received its first significant design update since 2010! More significantly, for the first time since 2006 it is not a wiki, but an actual language homepage. More significantly still, for the first time ever, the Haskell homepage now runs on a fully Haskell-powered stack. I suppose some people might also be interested in the fact that it looks quite nice, and has significantly cleaned up the information it presents, so as to provide a more focused experience for newcomers looking to explore the language. The page is now includes the collective work of over 230 commits by 17 contributors. First and foremost among those is Chris Done, who conceived the vision, wrote the bulk of the code, and executed the design. Also thanks to our many admins, including Austin Seipp, Ricky Elrod, et al., who managed the deployment, and have been working behind the scenes to continue to modernize and update our creaking infrastructure. Onto a few key things to remember
Categories: Offsite Discussion

Code review. API Guidance.

haskell-cafe - Sun, 02/15/2015 - 3:54am
Hello everyone. I have an application (a calculator repl [1]) and I'm looking to convert it into an package that provides both library and executable. I'm looking for suggestions for what might be a good API for such a library. I'm not looking for an extended code review, just the placement of functions in modules, and which functions to export. The current source tree looks like this. src/ $ tree . . ├── Calculator │ ├── Color.hs -- Colored output │ ├── Evaluator │ │ ├── Base.hs -- Common evaluation functions │ │ ├── Cmd.hs -- Evaluate special commands │ │ ├── Expr.hs -- Expression evaluation │ │ ├── Func.hs -- Convert specification for a function into a mathematical function │ │ └── Statement.hs -- Evaluate either expression or command │ ├── Help.hs -- Help message │ ├── Parser │ │ ├── Bas
Categories: Offsite Discussion

Exception safe resource management with dynamic regions, call for review

haskell-cafe - Sat, 02/14/2015 - 11:36pm
Hello, I'm asking for code and design review for `io-region` library. It is already on Hackage for convenience and easy access to haddock: Manual exception handling in Haskell almost never is a good idea, except probably trivial cases where `bracket` is enough. A number of special libraries where created to help with exception handling. `io-regions` is one of them. Initially it was an attempt to solve the double-throw issue, but I found it unsolvable in library without changes in language itself. So now it is an attempt to design easy to use API with a bit different set of trade-offs. The library is based on idea of regions that own resources. The resources are released when the region is closed. Early releasing and ownership transferring are supported. Types are *not* used to prevent use-after-free errors. The API is not monadic, and it is the biggest difference from other libraries. Regions are first-class citizens, so you can manipulate them, pass as arg
Categories: Offsite Discussion

New Haskell Homepage is Live

Haskell on Reddit - Sat, 02/14/2015 - 10:55pm finally has the result of the design that Chris Done first proposed last May. If you do not yet see it, the DNS should propagate soon, and then you will.

I think it looks pretty cool. There has been a long period of asking for feedback and pull-requests (you can find a link to the github repo at the bottom of the page). The page is now includes the collective work of 260 commits by 16 contributors. Thanks to everyone who tested it, commented on it, patched it, and otherwise helped get us to this point!

We imagine that now that this is the new official page, there will be more pull requests and issues, and the page will get even better. Note there is an issue tracker associated with the github repo, so we can log anything anyone wants to raise.

A lot of the work by our crack (but beleaguered) admin team has been in making sure all the "other stuff" transitions smoothly. So there are many subdirs like /ghc and they all should still work. If they don't, please let us know. Mailing lists have been moved to a new home at Redirects should be in place, and everything should work as before. If it doesn't, let us know.

If you're missing the old content -- it is all still there at and one of our first orders of business will be making it more prominent from the new page too.

As always, the way to contact your friendly neighborhood admin team is, or the #haskell-infrastructure channel on freenode, or -- in this case -- file a ticket (or better yet a pull request) on github.

submitted by gbaz1
[link] [116 comments]
Categories: Incoming News

ANN: ZuriHac 2015

haskell-cafe - Sat, 02/14/2015 - 10:15pm
We am glad to announce ZuriHac 2015, a annual three-day Haskell hackathon in Zurich. This year it's sponsored by Google. When: May 29th - May 31st Where: Google office, Zurich, Switzerland ZuriHac is an international Haskell hackathon: a grassroots, collaborative coding festival with a simple focus, to build and improve Haskell libraries, tools, and infrastructure. This is a great opportunity to meet your fellow Haskellers in real life, find new contributors for your project, improve existing libraries and tools, or even start new ones! I am happy to announce that Edward Kmett will give a talk. We are still in progress of nailing down the details, they will be available at the wiki page: Registration is not yet open, we will send an additional announcement email when it's open. We look forward to seeing you there!
Categories: Offsite Discussion

Inspecting functions

Haskell on Reddit - Sat, 02/14/2015 - 6:25pm


I dabble with Haskell every now and then and was wondering if anyone could suggest a good way to inspect the content of a function. C# has a system called an expression tree wherein a lambda expression is automatically converted by the compiler into a tree of objects, which can be inspected to generate code for other systems such as SQL in the case of Entity Framework; record => record.X > 3 && record.Y < 4 compiles to something like: And ( GreaterThan ( Member ( Parameter "record" ) "X" ) ( Constant 3 ) ) ( LessThan ( Member ( Parameter "record" ) "Y" ) ( Constant 4 ) ) which can be recursed to make a SQL query like: WHERE (X > 3) AND (Y < 4)

I see people making types which appear to work in a similar way, but this seems to me as though it would limit the flexibility and ease of use of "proper" functions; things like scope would be much harder to do.

My particular use case is that I have fairly complex distance field functions currently written as C# expressions which I want to be able to compute both on the CPU for physics and on the GPU for rendering as GLSL. I currently have a (quite shaky) proof-of-concept in C# but was wondering if Haskell could do this in another way.

Thank you.

submitted by JamesWildDev
[link] [5 comments]
Categories: Incoming News

How should I indent my code in Emacs?

Haskell on Reddit - Sat, 02/14/2015 - 3:59pm

I've been struggling with this ever since I started, and the more I try to configure my Emacs config, the worse it gets.

I've tried using hident, but out of the three available styles only the gibiansky one seems to work for the kind of code I write (the others split expressions way too much), but it still kills all the whitespace I've intentionally added, so I only rarely use it.

Out of the three indentation modes in Emacs, haskell-indent-mode, haskell-indentation-mode and haskell-simple-indent-mode, I can't find one that would just work. Most of the time I stick with haskell-indentation-mode, but recently it seems as if it went crazy and started indenting things differently.

Now I understand that it is really difficult to get indentation right in a language like Haskell, but I'm not looking for something to re-format my code, I only want proper indentation.

What do you guys use for indenting your Haskell code?

submitted by progfu
[link] [14 comments]
Categories: Incoming News

Changes to Haskell Weekly News: In with the Old,In with the New

haskell-cafe - Sat, 02/14/2015 - 3:56pm
Dear Reader, A few days ago Daniel Santa Cruz stepped down from the helm of Haskell Weekly News. With others that read HWN regularly, I thank him for his long service and wish him and his family godspeed. Did you know John Goerzen started HWN in August 2, 2005? Now a week from today, February 21, 2015, Simon and Simon shall close your window of opportunity to opine on drastic changes to the prelude. By sheer coincidence, the very first issue of HWN links to a thread on Updating the Haskell Standard. John himself started the thread. Today the talk is about the Foldable and Traversable type classes. Back then it was about Overlapping and Undecidable instances, the FFI, and a Hierarchical namespace. But these are all features we take for granted today. What sweeping changes took hold over the last ten years. There was no hackage. Only in September 2005 did Isaac Jones and David Himmelstrup announce beta-testing of a cabal prototype. Imagine life without hackage. Today there are 7664 packages all ready to
Categories: Offsite Discussion

ANN: ZuriHac 2015

Haskell on Reddit - Sat, 02/14/2015 - 2:43pm
Categories: Incoming News

type checker plugin does not affect inferred type signatures

glasgow-user - Sat, 02/14/2015 - 12:31pm
Hello, Using ghc-7.10 rc1, I am trying to write a type checker plugin that adds wanted constraint which helps ghc to infer more types. However, it seems that the wanted constraints I add don't get added to the inferred type of the declaration, so that I get a type error like: a.hs:1:1: Warning: Could not deduce (SameLength y x) arising from an application from the context (HLength x ~ HLength y) bound by the inferred type of p :: (HLength x ~ HLength y) => Proxy '(y, x) at a.hs:11:1-69 I think ghc should be able to figure out p :: (SameLength x y, HLength x ~ HLength y) => Proxy '(x,y). The code is self-contained: git clone cd HListPlugin/ex make Is this approach supposed to be possible, or am I supposed to rewrite things such that I only produce CtGivenS from the plugin? Regards, Adam
Categories: Offsite Discussion

Any recommendations on what GUI library I should use?

Haskell on Reddit - Sat, 02/14/2015 - 10:45am

Looking to make a basic GUI and was wondering what library would be best for this. It would be preferable if it ran on multiple operating systems :)

submitted by Apterygiformes
[link] [39 comments]
Categories: Incoming News

ANN: rasterific-svg & asciidiagram

Haskell on Reddit - Sat, 02/14/2015 - 7:39am

Single reddit submition for two new hackage packages:

submitted by heafiheihfaeiefh
[link] [1 comment]
Categories: Incoming News

GLUT + VSync?

Haskell on Reddit - Sat, 02/14/2015 - 7:23am

I am trying to make my first game in Haskell, a top-down space-craft shooter (how original!). Making good progress so far, but there is some horrible flickering going on as my background (a white grid so far) moves. I have already enabled Double Buffering, which stopped my ship from flickering, but the background issue is persistent. "Hmm", I thought to myself, "probably VSync". Some quick googling confirmed my thesis, but even after quite some more googling, I did not find a satisfying answer on how to enable VSync in GLUT. There was one comment stating it "needed to be hacked in", but didn't specify how. All the other solutions had nothing to do with the Haskell GLUT library. Can anyone please help me?

submitted by WSBoonami
[link] [10 comments]
Categories: Incoming News