February 2013 - Haskell-Cafe

Summer school on Applied Functional Programming at Utrecht University; deadline for registration May 15
by Doaitse Swierstra 02 May '13

02 May '13

Again we will teach an "Applied Functional Programming Summer in Haskell" school this year at Utrecht University. In the previous four occasions students were all very happy with the school and we plan to repeat this success this year. Among the intended audience are prospective master students who gained an interest in Functional Programming, e.g. by taking a general course on programming languages, and want to learn more about Haskell and its typical programming patterns. In previous years we have taught an introductory part (advanced bachelor level), an advanced part (beginning master level) and a shared part for both groups. Topics covered are, besides some examples of domain specific languages, also monads, monad transformers, arrows, parser combinators and self-analysing programs, underlying principles, type inferencing, etc. Half of the course time is spent on a larger programming exercise; you can also come with a problem of your own if you want, and get help from the Utrecht University Software Technology group in finding the proper Haskell idioms, tools and libraries, for solving it. Important links: -- our own page where we supply information based on questions asked http://www.cs.uu.nl/wiki/USCS/ -- on this page you can find the poster you can print and hang somewhere (why not your office door): Furthermore we ask for your cooperation to bring this announcement under the attention of potential participants. Best, Doaitse Swierstra, Atze Dijkstra and Johan Jeuring

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Ticking time bomb
by Edward Z. Yang 23 Mar '13

23 Mar '13

https://status.heroku.com/incidents/489 Unsigned Hackage packages are a ticking time bomb. Cheers, Edward

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Maintaining lambdabot
by Jan Stolarek 21 Mar '13

21 Mar '13

Hi all, as some of you may have noticed Lambdabot doesn't build on GHC 7.6.1 due to OldException being removed (and a few other changes). I updated the code so that it builds on latest GHC release. The updated code is available here: https://github.com/killy9999/lambdabot/tree/upstream It builds on Linux, but I am not 100% certain that it will build on Windows. If it doesn't I will be grateful for reporting this (and any other) issues on the bug tracker: https://github.com/killy9999/lambdabot/issues The changes required to make the code run weren't as small as I initially thought they will be. In some places this resulted in a bit ugly code, but aside from that I think that everything should work correctly. Now I would like to do a bit of maintanance on the project, since the code is a bit of a mess and it could use some cleanup. My plans are: - clean up the package namespace by placing existing modules in Lambdabot module - integrate lambdabot-utils into lambdabot (already done) - reformat the code so that it's easier to read ans if time allows: - cleanup some messy code - update the package dependencies so that lambdabot relies on maintained libraries (e.g. I thought about replacing readline with haskeline). This changes would be quite invasive and code wouldn't be compatible with the lambdabot repo on haskell.org. So before I start making any of them I would like to hear from the community if such changes in the source code of lambdabot would be considered helpful and acceptable. Janek

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Some aggregation of Haskell content
by Christopher Done 18 Mar '13

18 Mar '13

Is there a page somewhere that aggregates all of Haskell's community output into one place? As a consumer of Haskell content I neither have the time nor inclination to follow haskell-cafe and other various mailing lists, the reddits, the google+ community, planet haskell, hackage releases, twitter, youtube and whatever other submission places I haven't heard of. I made this page for the Lojban community some years ago: http://jbotcan.org/hub/ Lojban doesn't have much community activity (tho this doesn't include mailing list posts), but Haskell's community is much larger and more active, it would be far more useful. I may write such a page for Haskell content, if not for the community then at least for myself, as I keep missing out on cool things because I didn't happen to check out that particular medium of exchange. For example, even this message will be lost on a thousand people who doesn't follow the mailing list but maybe follows G+ or reddit. Kind of like a Haskell Weekly news, except more like "Haskell news right now or in some adjustable time frame." And the option to toggle between chronological order or categorized. Ciao!

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ANN: Nomyx 0.1 beta, the game where you can change the rules
by Corentin Dupont 03 Mar '13

03 Mar '13

Hello everybody! I am very happy to announce the beta release [1] of Nomyx, the only game where You can change the rules. This is an implementation of a Nomic [2] game in Haskell (I believe the first complete implementation). In a Nomyx game you can change the rules of the game itself while playing it. The players can submit new rules or modify existing ones, thus completely changing the behaviour of the game through time. The rules are managed and interpreted by the computer. They must be written in the Nomyx language, which is a subset of Haskell. At the beginning, the initial rules are describing: - how to add new rules and change existing ones. For example a unanimity vote is necessary to have a new rule accepted. - how to win the game. For example you win the game if you have 5 rules accepted. But of course even that can be changed! Here is a video introduction and first tutorial of the game: http://vimeo.com/58265498 The game is running here: www.nomyx.net:8000/Nomyx I have set up a forum where players can learn about Nomyx and discuss the rules they intend to propose: www.nomyx.net/forum As this is the first beta release of the game, I'm looking for beta testers :) Although I tested it quite a lot, I'm sure a lot of bugs remains, especially in multiplayer. So if you are interested in testing Nomyx, please go to this forum thread and we'll set up a small team to start a match! http://www.nomyx.net/forum/viewtopic.php?p=5 Comments/contributions are very highly welcome! There is still a lot to do. As for now, the game is not completely securised. It is easy to break it by submitting rules containing malicious code. I'm working on it. If you'd like to do security testing, please do it locally on your own machine and send me a bug report :). Cheers, Corentin [1] http://hackage.haskell.org/package/Nomyx [2] www.nomic.net

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Proposal: TypeDirectedNameResolution
by Johannes Waldmann 03 Mar '13

03 Mar '13

While browsing Haskell-Prime I found this: http://hackage.haskell.org/trac/haskell-prime/wiki/TypeDirectedNameResoluti… This is not some April Fool's day hoax? Because, it might actually turn Haskell into a somewhat usable (and marketable) language ... well, you know what I mean. Is there 'ghc -XTypeDirectedNameResolution' yet? - J.W.

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cabal install ghc-mod installs 3 years old version
by Niklas Hambüchen 01 Mar '13

01 Mar '13

Hi, I just did cabal update and cabal install ghc-mod, and for some reason it tries to install version 0.3.0 from 3 years ago: " cabal install ghc-mod -v Reading available packages... Choosing modular solver. Resolving dependencies... Ready to install ghc-mod-0.3.0 Downloading ghc-mod-0.3.0... " cabal --version cabal-install version 1.16.0.2 using version 1.16.0.3 of the Cabal library Does anyone have an idea why that could be? Thanks

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The state of binary (de)serialization
by Nicolas Trangez 01 Mar '13

01 Mar '13

All, In order to implement some network protocol clients recently, I needed binary serialization of commands and deserialization of responses ('Command -> ByteString' and 'ByteString -> Response' functions, preferably for both strict as well as lazy ByteStrings). My go-to packages have always been 'binary' and 'cereal', but I was wondering about the current (and future) state/goals: - cereal supports chunk-based 'partial' parsing (runGetPartial). It looks like support for this is introduced in recent versions of 'binary' as well (runGetIncremental) - cereal can output a strict bytestring (runPut) or a lazy one (runPutLazy), whilst binary only outputs lazy ones (runPut) - Next to binary and cereal, there's bytestring's Builder interface for serialization, and Simon Meier's "blaze-binary" prototype There are some blog posts and comments out there about merging cereal and binary, is this what's the goal/going on (cfr runGetIncremental)? In my use-case I think using Builder instead of binary/cereal's PutM monad shouldn't be a major problem. Is this advisable performance-wise? Overall: what's the advised future-proof strategy of handling binary (de)serialization? Thanks, Nicolas

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Split and substitution using regex-pcre
by Simon Marechal 28 Feb '13

28 Feb '13

I could not find the perl-equivalents of these functions on Hackage, so I quickly wrote mine. Code is there: https://github.com/bartavelle/pcre-utils It should behave like perl (not really tested actually), and do strange things like : > splitCompile "a" "aaaab" Right ["","","","","b"] > splitCompile "a" "aaaabaaa" Right ["","","","","b"] This will go on Hackage as I need it for the language-puppet package, but I am interested in comments, especially concerning the namespaces: * is the name of this package OK ? * is the name of the package OK ? * should I work with the regex-pcre maintainer to try to merge it ?

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How to return a network connection to C
by C K Kashyap 28 Feb '13

28 Feb '13

Hi, I am using Network.Connection to connect to gmail in my Haskell module - that's compiled to DLL and invoked from C. I need a mechanism to return the connection handle to C so that it can pass it in the subsequent calls. How can I achieve this? Regards, Kashyap

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