September 2011 - Haskell-Cafe

I for one welcome our new Robotic Overlords
by Jeremy Shaw 28 Sep '11

28 Sep '11

When the robots take over, do you want them to be developed using a sane language like Haskell or Agda? Or some dangerous untyped OO language? I think the answer is obvious. The question is, "How?". The robots will not be developed by us, but by the children of today. So, we must reach their pure minds before they have been unsafely coerced by the evil unbelievers who do not worship the gods λ, Π, and ω. My long term vision is: A company which produces an extensible robotics platform for children and adults ages 8 and up. The platform would be very open, extensible, and hackable. The robotic programming languages would be based around concepts like functional reactive programming, dependent types, etc. Children would begin with a simple FRP language to control the robot. They would solve simple problems like "go forward until an object is encountered." As the young masters grow, they can tackle more difficult problems such as maze solving. Even later they can delve into more advanced subjects like computer vision, speech recognition and synthesis, or mind control rays. The short term vision can be summarized in one word "leverage". We need to find an existing robotic platform which can be easily targeted somehow using Haskell or Agda. Perhaps something that can be targeted using atom or lava? Maybe something Arduino based? I have created a wiki page here to record your suggestions and ideas: http://haskell.org/haskellwiki/RoboticOverlords The requirements now are something that is: - hackable/open - easily obtained - reasonable in price - can easily be targeted via Haskell The only candidate I know of so far is lego mindstorms via the NXT package on hackage, Though some could argue that lego mindstorms are not reasonably priced. http://hackage.haskell.org/package/NXT Let's here your ideas! - jeremy

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Fwd: [Haskell] getting started
by Ivan Lazar Miljenovic 28 Sep '11

28 Sep '11

It helps if I actually CC the right mailing list... ---------- Forwarded message ---------- From: Ivan Lazar Miljenovic <ivan.miljenovic(a)gmail.com> Date: 28 September 2011 20:02 Subject: Re: [Haskell] getting started To: haskell <shubhammaheshwariy(a)gmail.com> Cc: cafe(a)haskell.org On 28 September 2011 19:56, haskell <shubhammaheshwariy(a)gmail.com> wrote: > i am new to haskell can you tell me the softwares to install in haskell > i have install hugs emacs > but when i write any code it gives same error can you help me start i have > lekash too i have installed some more packages Sending this over to the haskell-cafe(a)haskell.org mailing list (as that is where discussions take place, haskell(a)haskell.org is for announcements). You may wish to try the beginners mailing list however: http://www.haskell.org/mailman/listinfo/beginners If you want help, try providing the errors. However, I would recommend that you install the Haskell Platform instead of Hugs: http://hackage.haskell.org/platform/ -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com

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[ANN] crypto-api-tests
by Thomas DuBuisson 28 Sep '11

28 Sep '11

The crypto-api test modules have been split out into their own package, crypto-api-tests. Additionally, the tests now use the test-framework package. This should make it much easier for hash/cipher maintainers to integrate into their existing testing infrastructure. For example: $ cabal update ; cabal install cryptocipher crypto-api crypto-api-tests {- BEGIN CODE -} import Test.Framework import Test.AES (makeAESTests) import Crypto.Cipher.AES (AES128) main = do ts <- makeAESTests (a :: AES128) defaultMain ts {- END CODE -} $ ghc test.hs ; ./test ... snip ... OFBVarTxt128d.txt-125: [OK] OFBVarTxt128d.txt-126: [OK] OFBVarTxt128d.txt-127: [OK] Block Cipher tests (ident): ECBEncDecID: [OK, passed 100 tests] CBCEncDecID: [OK, passed 100 tests] CFBEncDecID: [OK, passed 100 tests] OFBEncDecID: [OK, passed 100 tests] CTREncDecID: [OK, passed 100 tests] Block Cipher tests (lazy/string bytestring equality): ECBStringLazyEq: [OK, passed 100 tests] CBCStrictLazyEq: [OK, passed 100 tests] CFBStrictLazyEq: [OK, passed 100 tests] OFBStrictLazyEq: [OK, passed 100 tests] CTRStrictLazyEq: [OK, passed 100 tests] Properties Test Cases Total Passed 10 2272 2282 Failed 0 0 0 Total 10 2272 2282 Patches for more algorithms and/or property tests for classes of algorithms are certainly welcome. Cheers, Thomas

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emacs literate haskell mode
by Mathijs Kwik 28 Sep '11

28 Sep '11

Hi all, I'm using haskell-mode for emacs and I'm using it to open a literate haskell file which uses latex. This works fine, haskell code has syntax highlighting, and special symbols like lambda get used. However, the latex itself is dull and gree, no highlighting/coloring there. Does anyone know if it's possible to turn on latex highlighting in literate haskell mode? I tried switching to latex-mode, which does the trick (but it chokes on the haskell code inbetween), so I'm pretty sure emacs has everything it needs, but haskell-mode needs to enable this somehow. Any help would be great. Greetings, Mathijs

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Re: [Haskell-cafe] mapM is supralinear?
by John Lato 27 Sep '11

27 Sep '11

> From: Daniel Fischer <daniel.is.fischer(a)googlemail.com> > > On Friday 09 September 2011, 00:41:11, Roman Cheplyaka wrote: >> * Ertugrul Soeylemez <es(a)ertes.de> [2011-09-07 16:20:03+0200] >> >> > In general it's a bad idea to use mapM over IO. >> >> Could you explain why? > > Take it with a grain of salt, there's nothing necessarily wrong with using > mapM over IO on short lists. Agreed. Whenever I'd like to use mapM (or any other function for which a *M_ is available), I've found the following rules helpful: 1. If I can guarantee the list is short (~ n<=20), go ahead and use mapM 2. Otherwise use mapM_, foldM_, or foldM if a real reduction is possible (i.e. not "foldM snocM []"). Step 2 sometimes requires changing my design, but it's always been for the better. `mapM_` tends to require more pipeline composition, so it's leveraging the language's strengths. This has served me well, especially in IO, but in other monads as well. John L.

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9th Ghent Functional Programming Group meeting on Tuesday, the 4th of October, 2011
by Jasper Van der Jeugt 27 Sep '11

27 Sep '11

Hello all, We are glad to invite you to our 9th GhentFPG [1] meeting, which takes place on Thursday, the 4th of October, 2011 at 19:30 in the Technicum building of Ghent University. You do not have to be a Functional Programming guru to attend, everyone eager to learn is welcome. As before, the electronic sliding doors will be locked, but a phone number that you can call to get in will be provided at the doors on the far left of the building. The program is as follows: First, we will have a talk by Jurriën Stutterheim, from Utrecht: Snap Framework [2] is a relatively young, but very promising and already quite popular Haskell web framework. Its upcoming 0.6 release has seen a major redesign in the way you write (reusable) components for the framework using so-called snaplets. In this talk, we will look at how you can write snaplets and how you can put them together to create modular web applications. Then, we will have a number of lightning talks in which the following projects are presented: - hCole-server [3], a web interface to a framework for compiler optimizations (Andy Georges); - GA [4], a library to write genetic algorithms in Haskell (Kenneth Hoste); - websockets [5], a Haskell library for writing WebSocket-capable servers (Jasper Van der Jeugt). If you would also like to give a lightning talk (15 mins), please contact us and we will add you to this list. Afterwards, we will have some drinks at a local bar. [1]: http://www.haskell.org/haskellwiki/Ghent_Functional_Programming_Group [2]: http://snapframework.com/ [3]: http://github.com/itkovian/hcole-server [4]: http://github.com/boegel/GA [5]: http://github.com/jaspervdj/websockets Hoping to see you there, The GhentFPG organizing commitee

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A Crypto-API-Tests package
by Thomas DuBuisson 27 Sep '11

27 Sep '11

FYI, since I figure you three are the ones interested in this right now: I'll be releasing crypto-api-tests [1] to hackage someday (this weekend?). If you want to give it a spin or add KATS before the first release then feel free. OTOH, it's not like I'd stop accepting patches after release 0.1. Cheers, Thomas [1] https://github.com/TomMD/crypto-api-tests

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which tags program should I use?
by Henry Laxen 26 Sep '11

26 Sep '11

Dear Group, I have a simple question, that as far as I can tell, has never really been well answered. I would like to generate TAGS files for haskell source. Reading the http://www.haskell.org/haskellwiki/Tags page suggests using :etags in GHCI or hasktags, or gasbag. Of the three, hasktags comes closest to "working" but it has (for me) a major inconvenience, namely it finds both function definitions and type signatures, resulting in two TAGS entries such as: ./Main.hs,63 module Main where6,7 main ::24,25 main =25,26 Now when I do an emacs find-tag (I use icicles) I will always have to choose which tag I want to visit, and the completion buffer contains something like: main :: hs/Main.hs main = hs/Main.hs Granted, this is a minor (and very specialized) complaint, but if hasktags were to select only ONE of either the type signature (my first choice) or the function definition, (if no type signature) this annoyance would disappear. I also tried using etags, which I think would work, but it seems to have one killer bug (feature), namely that it dies if it finds an uninterpreted import: when (not is_interpreted) $ let mName = GHC.moduleNameString (GHC.moduleName m) in ghcError (CmdLineError ("module '" ++ mName ++ "' is not interpreted")) I think it would work much better if it just warned you, instead of dying. This makes it unusable any time you import something precompiled. Now some looking at the README of hasktags leads me to: "In the past this tool was distributed with ghc. I forked and added some features. hasktags itself was moved out of the ghc repository. Then I only verified that my fork finds at least as much tags as the one forked by Igloo." That makes me feel a little queasy. A google search for hasktags igloo turns up http://hackage.haskell.org/trac/ghc/ticket/1508 whose title is "hasktags program needs replacement" which makes me feel even more queasy. So I guess my question is, what are us disciples of "the one true editor" to do? Thanks in advance for you sage advice. Best wishes, Henry Laxen

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Attoparsec: Limiting Parsers to N Bytes, or Combing Parsers?
by Michael Craig 26 Sep '11

26 Sep '11

Suppose we want to parse a 24-bit hex color value: input :: ByteString input = "af093c blah blah blah" type Color = (Word8, Word8, Word8) Attoparsec.Char8 exports a nice hexadecimal parser, but it consumes all available hex-flavored input. I'd like to make it consume exactly two bytes, so I could write my color parser like this: color :: Parser Color color = do r <- hex2 g <- hex2 b <- hex2 return $ Color (r, g, b) hex2 :: Parser Word8 hex2 = ??? So my question is "how do I write hex2?" I could easily rewrite hexadecimal, but it would be nicer to reuse its hex-handling logic. Best, Mike S Craig (908) 328 8030

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Job opportunities at Citrix Systems (Cambridge, UK)
by Mike McClurg 26 Sep '11

26 Sep '11

Hi folks, I just wanted to let everyone know that Citrix is hiring developers to work on the OCaml-based XenAPI toolstack. We are looking to recruit top-class engineers to work on the toolstack; applicants must have a good knowledge of data structures and algorithms, experience of programming in the context of large systems and general aesthetic good taste when it comes to code and architecture. Our code base is significant and varied: over 130,000 lines of OCaml, solving problems ranging from the low-level (Xen hypercalls) to the high-level (resource pool management), to the compiler-driven (generating language bindings for our Xen datamodel). Our ideal candidate will have: * significant experience with applications programming in high-level functional languages (such as OCaml) * an aptitude for implementing (and reasoning about) complex concurrent and distributed systems * the skills required to contribute to both the architectural design and day-to-day development of a large code-base * strong communication skills and problem solving ability * a determination to deliver clean and reliable solutions that meet our customers' needs So if you want to tackle interesting and challenging programming problems and contribute to an innovative, fast-growing product that is already used by tens of thousands of customers across the world, please don't hesitate to send me your CV. Thanks, Mike McClurg PS: Please note that you must have UK right to work. Here are the official job postings, but if you apply please send me your CV directly. * Req #11673 - Software Development Engineer: http://careers.peopleclick.com/careerscp/client_citrix/emea_region/jobDetai… * Req #11897 - Senior Software Developer: http://careers.peopleclick.com/careerscp/client_citrix/emea_region/jobDetai… And here are some links to our company, products and open source projects and code. * The Xen Hypervisor - http://xen.org/ * Citrix XenServer - http://www.citrix.com/English/ps2/products/product.asp?contentID=683148 * Our GitHub account - https://github.com/xen-org

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