July 2013 - Haskell-Cafe

Haskell Programmers for Distributed Systems
by Amanda Schwoegler 18 Jul '13

18 Jul '13

Parallel Scientific, Inc. is a Boulder, CO based, funded startup company with a presence around the globe, working in the cutting edge area of scalable parallelization. We seek experienced Haskell programmers to build a sophisticated, ultra-scalable high availability framework to be used in conjunction with scientific applications, big data applications and I/O systems. Successful candidates will work in a modern, virtual environment, with a distributed international team. All candidates are welcome to apply no matter their location. However, for this particular position, preference may be given to someone residing in or willing to relocate to the UK. Responsibilities include design, implementation in Haskell and in C, testing, infrastructure development, and optionally formal verification. We provide training in advanced processes for software design and implementation, as well as domain specific knowledge. Required skills: - Very strong background in computer science or mathematics. - Experience with Haskell, or network and cluster programming in other functional languages (e.g. Erlang, OCaml, Clojure). - Knowledge of systems programming and operating systems. Experience in one or more of the following areas is desirable: - Experience in distributed and/or parallel programming. - Knowledge of sophisticated distributed algorithms (fault tolerance, consensus, distributed transactions, etc). - Experience with delivering quality products on time and within budget. To apply, please send a resume to jobs(a)parsci.com. About Parallel Scientific Parallel Scientific was founded by Dr Peter Braam in 2010. Peter formerly taught mathematics and computer science at Oxford and Carnegie Mellon. He then contributed file systems to Linux and invented Lustre (which provides storage to 9 of the top 10 systems in the world). He ran several successful startups, and Parallel Scientific is run by a very experienced management team and board. Our expertise is in the areas of distributed scientific parallel computing, compilers, domain specific languages, scalable computing for cloud and HPC, and the synthesis of hardware appliances.

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what is wrong w my IORef Word32 ?
by Joerg Fritsch 18 Jul '13

18 Jul '13

All, what is wrong w the below code? I get an type error related to the operation shiftL import Data.Bits import Data.Word import Data.IORef data Word32s = Word32s { x :: IORef Word32 } bitfield :: Word32 bitfield = 0 mkbitfield :: Word32 -> IO Word32s mkbitfield i = do the_bf <- newIORef i return (Word32s the_bf) sLbitfield :: Integer -> Word32s -> IO () sLbitfield i (Word32s bf) = do modifyIORef bf (shiftL i) main::IO() main = do oper_bf <- mkbitfield bitfield sLbitfield 2 oper_bf bf_003.hs:15:48: Couldn't match type `Int' with `Word32' Expected type: Word32 -> Word32 Actual type: Int -> Word32 In the return type of a call of `shiftL' In the second argument of `modifyIORef', namely `(shiftL i)' In a stmt of a 'do' block: modifyIORef bf (shiftL i) bf_003.hs:15:55: Couldn't match expected type `Word32' with actual type `Integer' In the first argument of `shiftL', namely `i' In the second argument of `modifyIORef', namely `(shiftL i)' In a stmt of a 'do' block: modifyIORef bf (shiftL i) Thanks, --Joerg

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Re: [Haskell-cafe] Optimization flag changing result of code execution
by Azeem -ul-Hasan 18 Jul '13

18 Jul '13

I am using GHC 7.6.1 mwc-random 0.12.0.1 vector 0.9.1 primitive 0.4.1 Azeem On 16.03.2013 13:31, Azeem -ul-Hasan wrote: > Nope that isn't the case either. Even if I make use of defaultSeed > through create the problem still remains. The problem seems to be in the > generation of a vector of (a,a) i.e in the part > > V.generateM ((round $ p*(fromIntegral $ l*z)) `div` 2) (\i-> R.uniformR > ((0,0) , (l-1,l-1)) gen) > > in line 16. Thanks again. > I've tried to run you program and I've got approximately same results regardless of optimization level. Which versions of GHC, mwc-random, vector and primitive do you use?

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Haskell Weekly News: Issue 273
by Daniel Santa Cruz 17 Jul '13

17 Jul '13

Welcome to issue 273 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers the week of June 30 to July 13, 2013. Quotes of the Week * monochrom: 8-bit word uses less memory, but if it doesn't have to preserve information, I know how to use 0 bits of memory. * byorgey: you know, servers migrate in the summer to their ancestral breeding grounds * emeijer: It must me said on the other hand compiler writers seem to ignore the existence of formal semantics completely, probably because they don't like greek letters. * byorgey: now we have the pig operator <^(++)^> as well as the robot monkey operator (:[]) * chrisdone: i remember when the internet was black and white and you had to upload web pages back onto the internet when you were done with them * raganwald: Immuteability: The property of functional programmers that prevents them from shutting up about pure functional programming. Top Reddit Stories * On taking the last n elements of a list Domain: joachim-breitner.de, Score: 69, Comments: 37 On Reddit: [1] http://goo.gl/E9hRX Original: [2] http://goo.gl/9Uf74 * Comonads are NOT objects Domain: gelisam.blogspot.ca, Score: 62, Comments: 50 On Reddit: [3] http://goo.gl/tgdhh Original: [4] http://goo.gl/i3EDv * ANNOUNCE: Haste, the Haskell to JS compiler, is now on Hackage Domain: hackage.haskell.org, Score: 60, Comments: 27 On Reddit: [5] http://goo.gl/GTpj5 Original: [6] http://goo.gl/Nzpe7 * Postmodern Haskell and OpenGL: Introducing vinyl-gl Domain: arcadianvisions.com, Score: 57, Comments: 6 On Reddit: [7] http://goo.gl/9mVbl Original: [8] http://goo.gl/Zh5jE * ANNOUNCE: haskell-mode 13.07 (& Survey) Domain: projects.haskell.org, Score: 49, Comments: 18 On Reddit: [9] http://goo.gl/gYU24 Original: [10] http://goo.gl/YSmk4 * Why the world needs Haskell Domain: devalot.com, Score: 46, Comments: 22 On Reddit: [11] http://goo.gl/ekD96 Original: [12] http://goo.gl/LBxRP * Cartesian Closed Comic #20: Weird language Domain: ro-che.info, Score: 42, Comments: 10 On Reddit: [13] http://goo.gl/In50H Original: [14] http://goo.gl/tblYa * Do naming practices hurt Haskell? Domain: self.haskell, Score: 38, Comments: 222 On Reddit: [15] http://goo.gl/mnwO9 Original: [16] http://goo.gl/mnwO9 * ANNOUNCE: [17] http://goo.gl/pp0Vf Domain: self.haskell, Score: 37, Comments: 18 On Reddit: [18] http://goo.gl/MRDO7 Original: [19] http://goo.gl/MRDO7 * Skills Matter : In The Brain of Edsko de Vries: Lazy I/O and Alternatives in Haskell Domain: skillsmatter.com, Score: 37, Comments: 14 On Reddit: [20] http://goo.gl/13zlQ Original: [21] http://goo.gl/QSyTu * Attoparsec tutorial - School of Haskell Domain: fpcomplete.com, Score: 35, Comments: 17 On Reddit: [22] http://goo.gl/Riydl Original: [23] http://goo.gl/P2oiy * FP Haskell Center Beta Released and Beta Accounts Activated Domain: fpcomplete.com, Score: 33, Comments: 7 On Reddit: [24] http://goo.gl/Zs3kU Original: [25] http://goo.gl/vgy5m Top StackOverflow Questions * What advantage does Monad give us over an Applicative? votes: 17, answers: 7 Read on SO: [26] http://goo.gl/4L0gj * Encoding “Less Than” with Haskell votes: 11, answers: 1 Read on SO: [27] http://goo.gl/1Qsvn * Why is factorial calculation much faster in Haskell than in Java votes: 11, answers: 5 Read on SO: [28] http://goo.gl/QTbrl * Haskell: Can typeclasses define types (ala type traits) votes: 10, answers: 2 Read on SO: [29] http://goo.gl/yLSqT * C++ and Haskell codes differs in execution time on different machines votes: 10, answers: 1 Read on SO: [30] http://goo.gl/LRs3k * GHC.Generics or Data.Data? votes: 10, answers: 1 Read on SO: [31] http://goo.gl/yU6Ri * Constraint subset higher-order constraint votes: 9, answers: 1 Read on SO: [32] http://goo.gl/MTTws * How to make catamorphisms work with parameterized/indexed types? votes: 9, answers: 2 Read on SO: [33] http://goo.gl/FNSZg * How to “change” single values in large objects in elegant way? votes: 9, answers: 1 Read on SO: [34] http://goo.gl/3KuJj * What programming languages have something like Haskell’s `newtype` votes: 9, answers: 4 Read on SO: [35] http://goo.gl/vzUAI * Implementing a zipper for length-indexed lists votes: 8, answers: 1 Read on SO: [36] http://goo.gl/ja6VS * Does Haskell concatenate String literals at compile time? votes: 8, answers: 4 Read on SO: [37] http://goo.gl/sr61q * Combining lenses votes: 8, answers: 2 Read on SO: [38] http://goo.gl/qEbPd Until next time, [38]+Daniel Santa Cruz References 1. http://www.joachim-breitner.de/blog/archives/600-On-taking-the-last-n-eleme… 2. http://www.reddit.com/r/haskell/comments/1i64mt/on_taking_the_last_n_elemen… 3. http://gelisam.blogspot.ca/2013/07/comonads-are-neighbourhoods-not-objects.… 4. http://www.reddit.com/r/haskell/comments/1hficb/comonads_are_not_objects/ 5. http://hackage.haskell.org/package/haste-compiler 6. http://www.reddit.com/r/haskell/comments/1htqi2/announce_haste_the_haskell_… 7. http://www.arcadianvisions.com/blog/?p=388 8. http://www.reddit.com/r/haskell/comments/1hhrfn/postmodern_haskell_and_open… 9. http://projects.haskell.org/pipermail/haskellmode-emacs/2013-June/000188.ht… 10. http://www.reddit.com/r/haskell/comments/1hd21v/announce_haskellmode_1307_s… 11. http://www.devalot.com/articles/2013/07/why-haskell.html 12. http://www.reddit.com/r/haskell/comments/1hzz2d/why_the_world_needs_haskell/ 13. http://ro-che.info/ccc/20.html 14. http://www.reddit.com/r/haskell/comments/1i8e6v/cartesian_closed_comic_20_w… 15. http://www.reddit.com/r/haskell/comments/1i0uiq/do_naming_practices_hurt_ha… 16. http://www.reddit.com/r/haskell/comments/1i0uiq/do_naming_practices_hurt_ha… 17. http://www.reddit.com/r/haskell/comments/1i2a9l/announce_httphackagehaskell… 18. http://www.reddit.com/r/haskell/comments/1i2a9l/announce_httphackagehaskell… 19. http://skillsmatter.com/podcast/home/lazy-io-and-alternatives-in-haskell/jd… 20. http://www.reddit.com/r/haskell/comments/1i438a/skills_matter_in_the_brain_… 21. https://www.fpcomplete.com/school/attoparsec 22. http://www.reddit.com/r/haskell/comments/1hkg3g/attoparsec_tutorial_school_… 23. https://www.fpcomplete.com/blog/2013/06/fp-haskell-center-beta-announcement 24. http://www.reddit.com/r/haskell/comments/1hfbgs/fp_haskell_center_beta_rele… 25. http://stackoverflow.com/questions/17409260/what-advantage-does-monad-give-… 26. http://stackoverflow.com/questions/17578728/encoding-less-than-with-haskell 27. http://stackoverflow.com/questions/17584630/why-is-factorial-calculation-mu… 28. http://stackoverflow.com/questions/17398784/haskell-can-typeclasses-define-… 29. http://stackoverflow.com/questions/17412348/c-and-haskell-codes-differs-in-… 30. http://stackoverflow.com/questions/17502603/ghc-generics-or-data-data 31. http://stackoverflow.com/questions/17502985/constraint-subset-higher-order-… 32. http://stackoverflow.com/questions/17503131/how-to-make-catamorphisms-work-… 33. http://stackoverflow.com/questions/17518749/how-to-change-single-values-in-… 34. http://stackoverflow.com/questions/17591276/what-programming-languages-have… 35. http://stackoverflow.com/questions/17501777/implementing-a-zipper-for-lengt… 36. http://stackoverflow.com/questions/17513273/does-haskell-concatenate-string… 37. http://stackoverflow.com/questions/17528119/combining-lenses 38. https://plus.google.com/105107667630152149014/about

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ANNOUNCE: Aivika v0.6, Aivika Experiment v0.3, Aivika Experiment Chart v0.3
by David Sorokin 17 Jul '13

17 Jul '13

Hi! I’m glad to announce new versions of the Aivika [1] simulation library and its additional packages Aivika Experiment [2] and Aivika Experiment Chart [3]. The library is divided to decrease the dependency on GTK, although all three were tested on Linux, Windows and OS X. They allow developing the wide range of simulation models (SD, DES, AM), simulating them and saving the results in form of charts, tables and so on, automating many routine procedures. The architecture is quite flexible. This is a result of my 4-years work since 2009. I finally find the library a quite mature. Among many languages I tried, Haskell was the most suitable. Many simulation concepts can be naturally expressed in terms of Haskell. Many technical details are hidden either under the façade of monads, or similar structures. So, the ordinary differential equations can be elegantly defined using the recursive do-notation. But the discontinuous processes are well expressed using the continuations, if more precisely, three continuations in one computation. I prepared a 55-page PDF document An Introduction to Aivika Simulation Library [4]. For demonstration, it contains some charts prepared with help of Aivika Experiment Chart. There are the deviation charts and histograms. Thanks, David [1] http://hackage.haskell.org/package/aivika [2] http://hackage.haskell.org/package/aivika-experiment [3] http://hackage.haskell.org/package/aivika-experiment-chart [4] https://github.com/dsorokin/aivika/blob/master/doc/aivika.pdf

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Quoting with template haskell
by Jose A. Lopes 17 Jul '13

17 Jul '13

Hi everyone, I am quite new to template haskell and I am still trying to get the hang of it. How can I achieve something like the following Common Lisp code ? `(,fn ,arg1 ,arg2) Or is there a more Haskelley way of doing this ? Cheers, Jose

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Call for Papers PEPM 2014
by publicityifl＠gmail.com 17 Jul '13

17 Jul '13

Hello, Please, find below the first call for papers for PEPM 2014. Please forward these to anyone you think may be interested. Apologies for any duplicates you may receive. best regards, Jurriaan Hage Co-chair of PEPM 2014 ----------------------------- C A L L F O R P A P E R S ----------------------------- ======= PEPM 2014 =========== ACM SIGPLAN 2014 WORKSHOP ON PARTIAL EVALUATION AND PROGRAM MANIPULATION Mon-Tue, January 20-21, 2014 San Diego, California, USA co-located with POPL'14 Sponsored by ACM SIGPLAN http://www.program-transformation.org/PEPM14 SCOPE The PEPM Symposium/Workshop series aims at bringing together researchers and practitioners working in the areas of program manipulation, partial evaluation, and program generation. PEPM focuses on techniques, theory, tools, and applications of analysis and manipulation of programs. The 2014 PEPM workshop will be based on a broad interpretation of semantics-based program manipulation and continue last years' successful effort to expand the scope of PEPM significantly beyond the traditionally covered areas of partial evaluation and specialization and include practical applications of program transformations such as refactoring tools, and practical implementation techniques such as rule-based transformation systems. In addition, the scope of PEPM covers manipulation and transformations of program and system representations such as structural and semantic models that occur in the context of model-driven development. In order to reach out to practitioners, a separate category of tool demonstration papers will be solicited. Topics of interest for PEPM'14 include, but are not limited to: Program and model manipulation techniques such as: supercompilation, partial evaluation, fusion, on-the-fly program adaptation, active libraries, program inversion, slicing, symbolic execution, refactoring, decompilation, and obfuscation. Program analysis techniques that are used to drive program/model manipulation such as: abstract interpretation, termination checking, binding-time analysis, constraint solving, type systems, automated testing and test case generation. Techniques that treat programs/models as data objects including metaprogramming, generative programming, embedded domain-specific languages, program synthesis by sketching and inductive programming, staged computation, and model-driven program generation and transformation. Application of the above techniques including case studies of program manipulation in real-world (industrial, open-source) projects and software development processes, descriptions of robust tools capable of effectively handling realistic applications, benchmarking. Examples of application domains include legacy program understanding and transformation, DSL implementations, visual languages and end-user programming, scientific computing, middleware frameworks and infrastructure needed for distributed and web-based applications, resource-limited computation, and security. To maintain the dynamic and interactive nature of PEPM, we will continue the category of `short papers' for tool demonstrations and for presentations of exciting if not fully polished research, and of interesting academic, industrial and open-source applications that are new or unfamiliar. Student attendants with accepted papers can apply for a SIGPLAN PAC grant to help cover travel expenses and other support. PAC also offers other support, such as for child-care expenses during the meeting or for travel costs for companions of SIGPLAN members with physical disabilities, as well as for travel from locations outside of North America and Europe. For details on the PAC programme, see its web page. All accepted papers, short papers included, will appear in formal proceedings published by ACM Press. In addition to printed proceedings, accepted papers will be included in the ACM Digital Library. A special issue for Science of Computer Programming is planned with recommended papers from PEPM'14. PEPM has also established a Best Paper award. The winner will be announced at the workshop. SUBMISSION CATEGORIES AND GUIDELINES Regular Research Papers must not exceed 12 pages in ACM Proceedings style (including appendix). Tool demonstration papers and short papers must not exceed 6 pages in ACM Proceedings style (including appendix). At least one author of each accepted contribution must attend the workshop and present the work. In the case of tool demonstration papers, a live demonstration of the described tool is expected. Suggested topics, evaluation criteria, and writing guidelines for both research tool demonstration papers will be made available on the PEPM'14 Web-site. Papers should be submitted electronically via the workshop web site. Authors using LaTeX to prepare their submissions should use the new improved SIGPLAN proceedings style (sigplanconf.cls, 9pt template). IMPORTANT DATES Abstract due: Sat, September 28, 2013 Paper submission: Sat, October 5, 2013, 23:59, GMT Author notification: Mon, November 11, 2013 Camera-ready papers due: * to be announced * INVITED SPEAKERS to be announced PROGRAM CHAIRS Wei Ngan Chin (National University of Singapore, Singapore) Jurriaan Hage (Utrecht University, Netherlands) PROGRAM COMMITTEE velyne Contejean (LRI, CNRS, Universit Paris-Sud, France) Cristina David (University of Oxford, UK) Alain Frisch (LexiFi, France) Ronald Garcia (University of British Columbia, Canada) Zhenjiang Hu (National Institute of Informatics, Japan) Paul H J Kelly (Imperial College, UK) Oleg Kiselyov (Monterey, USA) Naoki Kobayashi (University of Tokyo, Japan) Jens Krinke (University College London, UK) Ryan Newton (University of Indiana, USA) Alberto Pardo (Universidad de la Repblica, Uruguay) Sungwoo Park (Pohang University of Science and Technology, South Korea) Tiark Rompf (Oracle Labs & EPFL, Switzerland) Sukyoung Ryu (KAIST, South Korea) Kostis Sagonas (Uppsala University, Sweden) Max Schaefer (Nanyang Technological University, Singapore) Harald S¿ndergaard (The University of Melbourne, Australia) Eijiro Sumii (Tohoku University, Japan) Eric Van Wyk (University of Minnesota, USA) Jeremy Yallop (University of Cambridge, UK)

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ANNOUNCE: module-management-0.9.3 - clean import lists, split and merge modules
by David Fox 16 Jul '13

16 Jul '13

I am pleased to announce the first release of module-management, a package for cleaning import lists, and splitting and merging modules. You can see a description at the top of the documentation for Language.Haskell.Modules (once it appears) here: http://hackage.haskell.org/package/module-management It is worth noting that the split and merge operations cause global changes to the module tree, all the modules that import the split or merged modules get their import lists adjusted. For this reason, before these operations can run the caller needs to specify the "moduVerse", the set of modules to scan for import changes. A number of bugs in GHC's -ddump-minimal-imports feature cropped up while I was writing this, and when the fixes for these issues make it into the compiler things will work a bit more smoothly, particularly if you are using NoImplicitPrelude or type families. http://hackage.haskell.org/trac/ghc/ticket/7963 http://hackage.haskell.org/trac/ghc/ticket/7969 http://hackage.haskell.org/trac/ghc/ticket/8000 http://hackage.haskell.org/trac/ghc/ticket/8011 There are workarounds for 7963 and 7969. Not surprisingly, template haskell can cause problems, but frequently it does not. CPP directives do not work. I hope you find this useful - all feedback is welcome! -david

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FP Complete Accepting Submissions for Haskell Competition
by Natalia Muska 16 Jul '13

16 Jul '13

We are excited to share we are accepting submissions for our *FP Haskell Competition<https://www.fpcomplete.com/business/competition/competition-overview> *. Your code and tutorials can earn you $1,000 in cash prizes each month. We're looking for sample Haskell projects that solve specific real-world engineering and business problems. There is no limit to how many projects you can submit or how many times you can win. - $1,000 cash prize for the winning entry each month - $500 each to the 3 runners-ups - There may be none at all if none meet the winning criteria The contest kicks off August 1, 2013. To participate, you'll need to sign up for our FP Haskell Center Beta<https://www.fpcomplete.com/business/haskell-center/overview>. We look forward to seeing your submissions and highlighting the talent of this great Haskell community. if you have any questions, please contact us at competition(a)fpcomplete.com. -- Natalia Muska Marketing Manager FP Complete, Inc. Natalia(a)fpcomplete.com 865-506-6513 skype: natalia.s.muska

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TH splicing and recompilation checking
by Johannes Waldmann 16 Jul '13

16 Jul '13

Hi. we are using template Haskell to splice in some code that is produced by reading and transforming the contents of another file. now, if this "other file" is touched (by editing), but not the main file, then ghc (and cabal) do not realize that the main file does need to be recompiled. is there a way to tell them about the dependency? (example main file: https://github.com/apunktbau/co4/blob/master/CO4/Test/Queens.hs) - J.W.

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