- Haskell-Cafe - Haskell.org

Haskell is a declarative language? Let's see how easy it is to declare types of things.
by Johannes Waldmann 05 Apr '13

05 Apr '13

I absolutely love to use Haskell when teaching (and I have several years of experience doing it). And I absolutely dislike it when I have to jump through hoops to declare types in the most correct way, and in the most natural places. This is hard to sell to the students. - Examples: 1. for explicit declaration of type variables, as in reverse :: forall (a :: *) . [a] -> [a] I have to switch on RankNTypes and/or KindSignatures (ghc suggests). C'mon, this has nothing to do with ranks per se. It's a type of a very simple function! IMHO even Java/C# do this better (with slightly strange syntax, but at least you get to declare the type variable). 2. for declaring types of local variables, as in \ (xs :: [Bool]) -> ... I have to enable PatternSignatures (actually ghc suggests ScopedTypeVariables but again there is no type variable in sight) I need to do this often, to disambiguate properties for Smallcheck. All of this just because it seemed, at some time, a clever idea to allow the programmer to omit quantifiers? (I know, mathematicians do this all over the place, but it is never helpful, and especially not when teaching.) I think that (1) implies (2): there could be no ambiguity about scopes (of typevars in patterns) if each typevar had to be introduced by explicit quantification. Then (in a pattern signature) a use could be distinguished from a declaration. Yes, the above is a rant. I can achieve what I want with some ghc options, and perhaps my point is that these should be on by default - or have better names, because presently, they are unintelligible to the (beginner) student.

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Haskell and WinRT
by Mark Flamer 05 Apr '13

05 Apr '13

There was a short thread on this in the beginners section a while back. I think it is an exciting subject and would like to hear what others thoughts are on it. The Windows 8 metro style apps are built using a new API that is designed to be exposed to other languages using "language projections" which are a thin wrapper around the windows runtime. Microsoft has provided these for C#, C++, Javascript & HTML and is encouraging language developers to create them for other languages. This seems like it might be the easiest rout to getting Haskell apps on tablets etc. with a modern UI. Simon Marlow discusses it briefly on this <https://plus.google.com/107890464054636586545/posts/PuFPongpyR4> page and there is a video on the topic here <http://channel9.msdn.com/Events/Lang-NEXT/Lang-NEXT-2012/The-Windows-Runtime> . Might even be a good summer of code project for someone. -- View this message in context: http://haskell.1045720.n5.nabble.com/Haskell-and-WinRT-tp5728106.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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Functional Programming Internship @ Intel
by Levent Erkok 05 Apr '13

05 Apr '13

[I'm posting on behalf of my colleague Jesse Bingham. While Jesse and I work for different groups at Intel, we collaborate quite often, and I do expect to work with the intern to an extent as well. To that end, I'm happy to answer any questions you might have. Otherwise, direct all correspondence to Jesse as indicated below. -Levent.] ================================================================= Hi, we are looking to hire an intern to fill the below position. If interested, please send your resume to jesse.d.bingham(a)intel.com. Thanks Intern SW Engr. Formal Verification - 708053 Description Design and Technology Solutions (DTS) creates the software that caters to Intel's insatiable appetite for innovating silicon technology. Through our CAD solutions and engineering services, we enable Intel's process engineers to achieve the technical breakthroughs required to deliver tomorrows technology, and we help Intel's architects and chip designers develop products that change the world. To us, Moore's law is the imperative that drives our work to continuously improve the ways we explore technology options, so we can deliver better products, faster. As a software engineer in DTS, you will work as part of a multi-disciplinary team to create software tools that meet Intel's specific, rapidly evolving requirements for designing, manufacturing, testing, and packaging silicon products. We work very closely with process engineers and chip designers (our internal customers) around the world, to understand their technical challenges, and to create proprietary CAD solutions. We help them apply our software to answer critical questions, and to address their design and manufacturing objectives. The daily work in DTS spans the complete software life cycle, from early research to mature production code with industrial robustness and quality. To deliver critical new features in our established solutions, or to create new CAD capabilities beyond the state of art in the industry, our teams frequently go through all steps in software development - problem analysis, requirements definition, design, coding, test, and deployment. As a member of our team, you are expected to participate actively in all these steps. Success in this fast-paced, results-oriented environment requires strong analytical skills and the ability to perform productive teamwork, which depends on very good communication skills. In this particular job opening, you will join DTS's Formal Verification Center of Expertise (FVCoE) for a three month placement in Hillsboro, Oregon, in the timeframe of fall 2013. A primary responsibility of FVCoE is the maintenance of a large code base used for formal verification of Intel's core datapath designs; you will help rework several key aspects of this code to make it more robust and user-friendly. This will involve strict software engineering discipline to deliver robust, quality code that must perform reliably and predictably, The code is written in an in-house functional language called reflect. Reflect is similar to the popular functional languages Ocaml and Haskell; hence you should have considerable experience with one of these. Experience with formal verification is preferred but not necessarily required. Applicants will ideally be working towards a graduate degree in Computer Science or a related discipline. Qualifications Minimum Requirements Skills: Functional programming coding skills; experience with one or more scripting languages; analytical skills for problem abstraction; broad theoretical knowledge in computer science, including algorithms and data structures; familiarity with standard software engineering practices. Experience: acquired through coursework, internships, or personal projects. Experience in applied computer programming in a functional language. Education: working toward an MS or Ph.D. degree in Computer Science, Applied Mathematics, or in an Engineering field related to silicon technology. Strong senior undergraduates will also be considered. Preferred Requirements Skills: Familiarity with: hardware formal verification techniques (especially symbolic simulation, binary decision diagrams, parametric substitutions, case splitting), arithmetic/floating point computer hardware designs, IEEE 754 floating point standard, Intel x86 instruction set.

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Possible GSoC project
by Ketil Malde 04 Apr '13

04 Apr '13

Hi, I proposed a bioinformatics GSoC project involving Haskell using OSC as the mentoring organization. Typically, haskell.org projects concern infrastructure rather than applications, and I don't know if I'm allowed to submit both places :-) Anyway, as this is a likely place to find prospective students and (co-)mentors, I thought I'd mention it here. But if anybody is interested, I think it makes for a quite focused, solvable problem, which I belive would be quite useful. It could also likely result in a scientific publication of some sort. A quick writeup (that I'll probably update) is here: http://biohaskell.org/Google_Summer_of_Code#optimizing-transalign -k -- If I haven't seen further, it is by standing in the footprints of giants

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Re: [Haskell-cafe] [Haskell] ANN: adobe-swatch-exchange-0.1.0.0
by Brent Yorgey 04 Apr '13

04 Apr '13

(Redirecting follow-up to haskell-cafe) Very cool! I have been hoping someone will find a way to integrate kuler.adobe.com with diagrams, and this will help a lot. =) https://github.com/diagrams/diagrams-lib/issues/77 -Brent On Wed, Apr 03, 2013 at 06:49:34PM -0500, Jeremy Shaw wrote: > I am pleased to annouce the release of adobe-swatch-exchange 0.1.0.0. > > My primary motivation in writing this is to make it easier to download > color swatches from http://kuler.adobe.com/ and test them on my site. > Though, perhaps there is already a great way of doing this and I > didn't look hard enough. > > But, the end result is we can now read and write .ASE files in Haskell > and convert them to .css. So that probably opens up some new > possibilities. > > I have provided both a library and an executable. > > I have also used this as a way to test the waters with github, > > https://github.com/stepcut/ase2css > > I heard putting things on github will get me all sorts of > contributors. I suggest someone start with haddock comments. ;) > > Cheers! > - jeremy > > _______________________________________________ > Haskell mailing list > Haskell(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell

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Resource Limits for Haskell
by Edward Z. Yang 04 Apr '13

04 Apr '13

Hey folks, Have you ever wanted to implement this function in Haskell? -- | Forks a thread, but kills it if it has more than 'limit' -- bytes resident on the heap. forkIOWithSpaceLimit :: IO () -> {- limit -} Int -> IO ThreadId Well, now you can! I have a proposal and set of patches here: http://hackage.haskell.org/trac/ghc/wiki/Commentary/ResourceLimits http://hackage.haskell.org/trac/ghc/ticket/7763 There is a lot of subtlety in this space, largely derived from the complexity of interpreting GHC's current profiling information. Your questions, comments and suggestions are greatly appreciated! Cheers, Edward

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Type level natural numbers
by Mateusz Kowalczyk 04 Apr '13

04 Apr '13

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 About two weeks ago we got an email (at ghc-users) mentioning that comparing to 7.6, 7.7.x snapshot would contain (amongst other things), type level natural numbers. I believe the package used is at [1]. Can someone explain what use is such package in Haskell? I understand uses in a language such as Agda where we can provide proofs about a type and then use that to perform computations using the type system (such as guaranteeing that concatenating two vectors together will give a new one with the length of the two initial vectors combine) however as far as I can tell, this is not the case in Haskell (although I don't want to say ?impossible? and have Oleg jump me). - -- Mateusz K. -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (GNU/Linux) iQIcBAEBAgAGBQJRXIYYAAoJEM1mucMq2pqXT00P/imTf/Wd7UZ0T0ZPUbM6i3Nj P5ffEUvUGf5V1jmXub/ibVFv6QHkTigsF/K9VPo13ChtA7u4qnxH7pd+zbTCp6c4 +A4dgKLVvlB+tGSvKzmsJxEtRh/rtv0UMP2RtvKoB7DH2mMv99EDkKmndWaxOI2z VjAvYFqdi//3O0P9bN9/93KZNUZviHh/5IP8f6HcpCWVDu+Z5CKbzUM6roxsBNM1 a1y6RjQp2SnUFMlJnKbWepRbn2p12dzmMrXzF2UINkTkDTytP+ZIK1ZpS8/qh6i6 q44GUBa2doHxhX9H+Vo3Vims3S0otyVmTQX/b2J1R7FoBl6fsPa+XUeE8RJwfSzm 0Ho75AX39rynO9AJ+/hZQdk6G6VkED/JszWBSnfC56VNB0vdYI4e2mBGny4uL9MU PnVb+fYk0xuSw7wAqLnVo2ZQqyvN79uNDT4x0uf/6zvkQ8LoSzMr99YwjWI5jo2X 8dqphjPPArX9MV0xCPdkpU6wPHSvEK4fOxJcqDq104+ssJdNr8PXbhtIifa/KE/C B2jhmwRllbtbg1HGXQ8zWlY+VbE+sc5O2AvhrV14fKF8xkNtLRzvhAWR/cOTXLZ0 hA7r6Jjf4mzQnUBgb/BW8pH6N+UnjkV/JgJ45WHB3PSADU3JspyuG7uJUOCod75e D/849dOCHHrkYsYEPdJq =JCfK -----END PGP SIGNATURE-----

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Re: [Haskell-cafe] Threadscope 0.2.2 goes in segmentation fault on Mac Os X 10.8.3
by Dominic Steinitz 04 Apr '13

04 Apr '13

Alfredo Di Napoli <alfredo.dinapoli <at> gmail.com> writes: > > Said that,has someone had any luck in running Threadscope on Mac OS X 10.8 at all? > > Thanks, > A. > I think I have encountered the same problem: https://groups.google.com/d/msg/parallel-haskell/-lhrgNN8elw/KzqLM9BzoJwJ In my experience, anything that uses gtk is a problem on a MAC. I still intend to do some analysis *not* using threadscope but using event-logs directly but that is at least a few weeks away. Dominic.

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install cuda
by Peter Caspers 04 Apr '13

04 Apr '13

Hi, I am trying to install the cuda package on a Windows 7 enviroment. However I run into an error and can not figure out, what it is. Can someone help ? Thanks a lot Peter C:\Users\Peter\_dev\haskell>cabal install cuda Resolving dependencies... [1 of 1] Compiling Main ( C:\Users\Peter\AppData\Local\Temp\cuda-0.5.0.1-11856\cuda-0.5.0.1\Setup.hs, C:\Users\Peter\AppData\Local\Temp\cuda-0.5.0.1 -11856\cuda-0.5.0.1\dist\setup\Main.o ) Linking C:\Users\Peter\AppData\Local\Temp\cuda-0.5.0.1-11856\cuda-0.5.0.1\dist\setup\setup.exe ... Configuring cuda-0.5.0.1... cygwin warning: MS-DOS style path detected: C:\Users\Peter\AppData\Roaming\cabal/share/config.site Preferred POSIX equivalent is: /cygdrive/c/Users/Peter/AppData/Roaming/cabal/share/config.site CYGWIN environment variable option "nodosfilewarning" turns off this warning. Consult the user's guide for more details about POSIX paths: http://cygwin.com/cygwin-ug-net/using.html#using-pathnames checking for gcc... C:\Program Files (x86)\Haskell Platform\2012.4.0.0\mingw\bin\gcc.exe checking whether the C compiler works... no configure: error: in `/cygdrive/c/Users/Peter/AppData/Local/Temp/cuda-0.5.0.1-11856/cuda-0.5.0.1': configure: error: C compiler cannot create executables See `config.log' for more details cabal: Error: some packages failed to install: cuda-0.5.0.1 failed during the configure step. The exception was: ExitFailure 77

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Haskell Weekly News: Issue 264
by Daniel Santa Cruz 04 Apr '13

04 Apr '13

Welcome to issue 264 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers the week of March 17 to 30, 2013. Quotes of the Week * ddarius: (f x) is a partial application iff f x == (curry (uncurry f) x) * flebron: "Hey, I am Haskell; and this is lazy; so here's a function; I'll call it, maybe." * WinstonChurchill: It is a good thing for an uneducated man to read books of quotations. * ab9rf: (on duck typing) if you want a duck-submarine-employee-tomato, you can do that * johnw: Stealing lens from the gods, and then having my liver eaten out daily. * dibblego: scala puts road blocks in your way proportional to how effective you want to be * hiptobecubic: I want my programs to either be correct or violently explode * shachaf: edwardk will try to get you addicted to monoids. The first one is always free. * merijn: So apparently there's a footballer named lens, who played some important part in the match against the Netherlands... Which would explain the fact that twitter is telling me "lens" is trending, I was starting to think haskell had won the PL revolution with edwardk as our glorious leader ;) * elliott: all I want for christmas is a boring lambdabot. Top Reddit Stories * What’s good for C++ is good for … Haskell!? Domain: serpentine.com, Score: 101, Comments: 20 On Reddit: [1] http://goo.gl/B8Km5 Original: [2] http://goo.gl/tCB0a * Anatomy of Programming Languages (in Haskell) Domain: self.haskell, Score: 72, Comments: 29 On Reddit: [3] http://goo.gl/YmO5M Original: [4] http://goo.gl/YmO5M * Programming and Reasoning with Algebraic Effects and Dependent Types Domain: edwinb.wordpress.com, Score: 58, Comments: 28 On Reddit: [5] http://goo.gl/xfH0Z Original: [6] http://goo.gl/AdGEJ * School of Haskell—Basic Lensing Domain: fpcomplete.com, Score: 57, Comments: 39 On Reddit: [7] http://goo.gl/JIowk Original: [8] http://goo.gl/NX1ak * Haskell for all: mmorph-1.0.0: Monad morphisms Domain: haskellforall.com, Score: 56, Comments: 18 On Reddit: [9] http://goo.gl/nlHfN Original: [10] http://goo.gl/6aHZt * Haskell News Domain: haskellnews.org, Score: 43, Comments: 12 On Reddit: [11] http://goo.gl/fNzzI Original: [12] http://goo.gl/4K1tD * pipes-3.2: ListT, Codensity, ArrowChoice, and performance Domain: haskellforall.com, Score: 43, Comments: 19 On Reddit: [13] http://goo.gl/a0xm8 Original: [14] http://goo.gl/RFLdw * Introducing diagrams-haddock Domain: byorgey.wordpress.com, Score: 41, Comments: 13 On Reddit: [15] http://goo.gl/d5Vl5 Original: [16] http://goo.gl/PmUFs * Optimising Purely Functional GPU Programs Domain: justtesting.org, Score: 41, Comments: 2 On Reddit: [17] http://goo.gl/ZgiXt Original: [18] http://goo.gl/M5fop * Creating board games in Haskell in 100 lines of code Domain: keera.co.uk, Score: 38, Comments: 30 On Reddit: [19] http://goo.gl/lbZke Original: [20] http://goo.gl/epwqQ * What is the logarithm or root operation in type-space? (x-post from r/compsci) Domain: cstheory.stackexchange.com, Score: 38, Comments: 17 On Reddit: [21] http://goo.gl/1z3a9 Original: [22] http://goo.gl/JXAlC * New GHC Extension - Nullary Type Classes (apparently not an April Fool's joke) Domain: hackage.haskell.org, Score: 37, Comments: 24 On Reddit: [23] http://goo.gl/rD5KC Original: [24] http://goo.gl/drfb7 * The Monad.Reader issue 21 Domain: themonadreader.files.wordpress.com, Score: 30, Comments: 2 On Reddit: [25] http://goo.gl/R1dke Original: [26] http://goo.gl/nGHjP * Dependently Typed Functional Programming with Idris 4 (last lecture) Domain: vimeo.com, Score: 28, Comments: 4 On Reddit: [27] http://goo.gl/ozbtK Original: [28] http://goo.gl/2xsaB * Conal Elliot: Folds and Unfolds Domain: conal.net, Score: 28, Comments: 5 On Reddit: [29] http://goo.gl/ZzFZ1 Original: [30] http://goo.gl/JVQK4 * Mihai-Radu Popescu's book in progress: "Speeding Through Haskell" Domain: sthaskell.com, Score: 26, Comments: 15 On Reddit: [31] http://goo.gl/d1wZF Original: [32] http://goo.gl/oB0e8 * hchip - a Haskell emulator for Chip16 Domain: self.haskell, Score: 25, Comments: 1 On Reddit: [33] http://goo.gl/mtHhg Original: [34] http://goo.gl/mtHhg * Introduction to Haskell, Lecture 8 is Live (Monads) Domain: shuklan.com, Score: 25, Comments: 22 On Reddit: [35] http://goo.gl/nCV1q Original: [36] http://goo.gl/D4VGn * School of Haskell: Learning Haskell Through Koans Domain: fpcomplete.com, Score: 22, Comments: 2 On Reddit: [37] http://goo.gl/sKxmz Original: [38] http://goo.gl/2n9aF * Arrow Notation in Functional Reactive Programming demonstrated with a simple OpenGL demo (Yampa) Domain: youtube.com, Score: 22, Comments: 9 On Reddit: [39] http://goo.gl/NN8nr Original: [40] http://goo.gl/m5XEb Top StackOverflow Questions * Maintaining complex state in Haskell votes: 23, answers: 1 Read on SO: [41] http://goo.gl/XbFtx * Is using mapM/sequence considered good practice? votes: 14, answers: 3 Read on SO: [42] http://goo.gl/juA3q * Can I model a list of successes with short circuiting failure via the composition of applicative functors? votes: 12, answers: 2 Read on SO: [43] http://goo.gl/biKxw * Understanding Polytypes in Hindley-Milner Type Inference votes: 12, answers: 2 Read on SO: [44] http://goo.gl/sjzJJ * Why add “Eq” type constraint without using “==”? votes: 11, answers: 1 Read on SO: [45] http://goo.gl/hljhA * :: a -> (a -> b) -> b operator (Haskell) votes: 11, answers: 3 Read on SO: [46] http://goo.gl/O643o * What's the most efficient way to represent finite (non-recursive) algebraic type values? votes: 10, answers: 2 Read on SO: [47] http://goo.gl/ikN78 * What's the “easier way” that deprecates the need for Data.Conduit.Util's zip? votes: 10, answers: 1 Read on SO: [48] http://goo.gl/kk6jq * Haskell equivalent of scala collect votes: 10, answers: 1 Read on SO: [49] http://goo.gl/wjKTR * Scheduling a Timeout in Haskell votes: 10, answers: 1 Read on SO: [50] http://goo.gl/Pya8z Until next time, +Daniel Santa Cruz References 1. http://www.serpentine.com/blog/2013/03/20/whats-good-for-c-is-good-for-hask… 2. http://www.reddit.com/r/haskell/comments/1aok5k/whats_good_for_c_is_good_fo… 3. http://www.reddit.com/r/haskell/comments/1b4m75/anatomy_of_programming_lang… 4. http://www.reddit.com/r/haskell/comments/1b4m75/anatomy_of_programming_lang… 5. https://edwinb.wordpress.com/2013/03/28/programming-and-reasoning-with-alge… 6. http://www.reddit.com/r/haskell/comments/1b64xh/programming_and_reasoning_w… 7. https://www.fpcomplete.com/user/tel/basic-lensing 8. http://www.reddit.com/r/haskell/comments/1anf0n/school_of_haskellbasic_lens… 9. http://www.haskellforall.com/2013/03/mmorph-100-monad-morphisms.html 10. http://www.reddit.com/r/haskell/comments/1ahyzu/haskell_for_all_mmorph100_m… 11. http://haskellnews.org/ 12. http://www.reddit.com/r/haskell/comments/1ahgrn/haskell_news/ 13. http://www.haskellforall.com/2013/03/pipes-32-listt-codensity-arrowchoice.h… 14. http://www.reddit.com/r/haskell/comments/1av2gi/pipes32_listt_codensity_arr… 15. http://byorgey.wordpress.com/2013/03/23/introducing-diagrams-haddock/ 16. http://www.reddit.com/r/haskell/comments/1aw33e/introducing_diagramshaddock/ 17. http://justtesting.org/optimising-purely-functional-gpu-programs 18. http://www.reddit.com/r/haskell/comments/1bapa5/optimising_purely_functiona… 19. http://keera.co.uk/blog/2013/03/19/creating-board-games-in-haskell/ 20. http://www.reddit.com/r/haskell/comments/1ani3n/creating_board_games_in_has… 21. http://cstheory.stackexchange.com/questions/17006/what-is-the-logarithm-or-… 22. http://www.reddit.com/r/haskell/comments/1aynxj/what_is_the_logarithm_or_ro… 23. http://hackage.haskell.org/trac/ghc/ticket/7642 24. http://www.reddit.com/r/haskell/comments/1atlvu/new_ghc_extension_nullary_t… 25. http://themonadreader.files.wordpress.com/2013/03/issue21.pdf 26. http://www.reddit.com/r/haskell/comments/1ahrii/the_monadreader_issue_21/ 27. http://vimeo.com/62059837 28. http://www.reddit.com/r/haskell/comments/1aisv0/dependently_typed_functiona… 29. http://conal.net/talks/folds-and-unfolds.pdf 30. http://www.reddit.com/r/haskell/comments/1asxuf/conal_elliot_folds_and_unfo… 31. http://www.sthaskell.com/ 32. http://www.reddit.com/r/haskell/comments/1azvcy/mihairadu_popescus_book_in_… 33. http://www.reddit.com/r/haskell/comments/1akhgi/hchip_a_haskell_emulator_fo… 34. http://www.reddit.com/r/haskell/comments/1akhgi/hchip_a_haskell_emulator_fo… 35. http://shuklan.com/haskell/lec09.html 36. http://www.reddit.com/r/haskell/comments/1alqjq/introduction_to_haskell_lec… 37. https://www.fpcomplete.com/blog/2013/03/learning-through-koans 38. http://www.reddit.com/r/haskell/comments/1amuuz/school_of_haskell_learning_… 39. http://www.youtube.com/watch?v=T3xXebIr8AM#t=17m58s 40. http://www.reddit.com/r/haskell/comments/1ao4nx/arrow_notation_in_functiona… 41. http://stackoverflow.com/questions/15467925/maintaining-complex-state-in-ha… 42. http://stackoverflow.com/questions/15546216/is-using-mapm-sequence-consider… 43. http://stackoverflow.com/questions/15460794/can-i-model-a-list-of-successes… 44. http://stackoverflow.com/questions/15497315/understanding-polytypes-in-hind… 45. http://stackoverflow.com/questions/15512541/why-add-eq-type-constraint-with… 46. http://stackoverflow.com/questions/15604290/a-a-b-b-operator-haskell 47. http://stackoverflow.com/questions/15572996/whats-the-most-efficient-way-to… 48. http://stackoverflow.com/questions/15627359/whats-the-easier-way-that-depre… 49. http://stackoverflow.com/questions/15634549/haskell-equivalent-of-scala-col… 50. http://stackoverflow.com/questions/15671328/scheduling-a-timeout-in-haskell 51. https://plus.google.com/105107667630152149014/about

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