July 2013 - Haskell - Haskell.org

Re: [Haskell] [Haskell-cafe] ANNOUNCE: MFlow 3.0
by Alberto G. Corona 10 Jul '13

10 Jul '13

Thanks Adrian. The racket people where pioneers in this idea I think. There is another web framework in Ocaml, Osigen that it is also continuation based. MFlow is not continuation-based but it also define the navigation as a sequence. But only Seaside (and now MFlow) supports many flows in the same page. See for example this: [PDF] *Seaside* – A *Multiple* Control *Flow* Web Application Framework<http://www.google.es/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=3&cad=rja…> There is also other: Apache Coccoon that run in a special kind of JavaScript. The continuation-based frameworks have the reputation of storing a lot of application state and to be non scalable. MFlow uses backtracking and It does not have these problems. 2013/7/10 Adrian May <adrian.alexander.may(a)gmail.com> > Oh how nice! > > I have been looking at MFlow a lot lately and I think it's got something > quite special that Yesod, Happstack, etc don't seem to have, at least, not > as far as I know. I mean, look at this: > > sumWidget= pageFlow "sum" $ do > > n1 <- p << "Enter first number" ++> getInt Nothing <** submitButton "enter" <++ br > > n2 <- p << "Enter second number" ++> getInt Nothing <** submitButton "enter" <++ br > > n3 <- p << "Enter third number" ++> getInt Nothing <** submitButton "enter" <++ br > > p << ("The result is: "++show (n1 + n2 + n3)) ++> wlink () << b << " menu" > > <++ p << "you can change the numbers in the boxes to see how the result changes" > > Is that pretty or what? That's the code for this: > > http://mflowdemo.herokuapp.com/noscript/fviewmonad > > To me that's a real technological step over and above the usual servlets > paradigm and I'd love to see more people getting involved. It seems like > Yesod and Happstack have a lot more manpower behind them, but unless I've > missed something, MFlow is going somewhere new and should be helped along. > > Adrian. > > PS. Besides Seaside, Racket is playing with the same ideas. They (Jay > McCarthy) have something to say about performance but I didn't quite > understand it. > > > > On 10 July 2013 06:41, Alberto G. Corona <agocorona(a)gmail.com> wrote: > >> The third version of MFlow is out. >> >> http://hackage.haskell.org/package/MFlow >> >> MFlow is an all-heterodox web application framework, but very haskellish. >> >> Now MFlow support restful URLs. It is the first stateful web framework >> to my knowledge that supports it. The type safe routes are implicitly >> expressed as normal monadic code within a navigation monad. The application >> look as a normal imperative console application, but the navigation monad >> goes back and forth to match the path of the URL. The user has control of >> the state, that can roll-back or not when the navigation goes back >> depending on the application needs. The state is in the form of normal >> Haskell variables In a monadic computation, with the weird addition of >> backtracking. >> >> The menu of the application below is implemented as an imperative-like >> syntax, but the application navigate forward and backward to synchronize >> with the requests of the web browser: >> http://mflowdemo.herokuapp.com/ >> >> This version support in-page flows. >> What is that? look at this example: >> >> http://mflowdemo.herokuapp.com/noscript/fviewmonad >> >> These flows are implemented as formlets with a monad instance, and >> callbacks which change the look. I call them "widgets": >> >> >> http://haskell-web.blogspot.com.es/2013/06/the-promising-land-of-monadic-fo… >> >> >> Each page may have many of these active widgets, each one running their >> own flow. These widgets refresh themselves trough Ajax if they are enclosed >> in the primitive "autoRefresh". If there is no Ajax or JavaScript >> available, they gracefully degrade by refreshing the entire page: >> >> http://mflowdemo.herokuapp.com/noscript/combination >> >> >> http://haskell-web.blogspot.com.es/2013/06/and-finally-widget-auto-refreshi… >> >> The page flows and the multiflow idea was inspired in Seaside<http://www.seaside.st/>, >> a great Smalltalk web framework and adapted to the pure recursive nature of >> Haskell and the formlets. >> >> It also support some JQuery widgets integrated: modal and not modal >> dialogs, datePicker and other active widgets that handle other widgets. >> >> It also support the older features: persistent state, WAI, blaze-html and >> others integration, server process timeouts, Ajax, requirements, >> content management, caching of widget rendering and all the other >> previous stuff. >> >> I wish to thank some people for their feedback. Specially Adrian May for >> his feedback and interest >> >> >> -- >> Alberto. >> >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe >> >> > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > > -- Alberto.

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ANNOUNCE: MFlow 3.0
by Alberto G. Corona 09 Jul '13

09 Jul '13

The third version of MFlow is out. http://hackage.haskell.org/package/MFlow MFlow is an all-heterodox web application framework, but very haskellish. Now MFlow support restful URLs. It is the first stateful web framework to my knowledge that supports it. The type safe routes are implicitly expressed as normal monadic code within a navigation monad. The application look as a normal imperative console application, but the navigation monad goes back and forth to match the path of the URL. The user has control of the state, that can roll-back or not when the navigation goes back depending on the application needs. The state is in the form of normal Haskell variables In a monadic computation, with the weird addition of backtracking. The menu of the application below is implemented as an imperative-like syntax, but the application navigate forward and backward to synchronize with the requests of the web browser: http://mflowdemo.herokuapp.com/ This version support in-page flows. What is that? look at this example: http://mflowdemo.herokuapp.com/noscript/fviewmonad These flows are implemented as formlets with a monad instance, and callbacks which change the look. I call them "widgets": http://haskell-web.blogspot.com.es/2013/06/the-promising-land-of-monadic-fo… Each page may have many of these active widgets, each one running their own flow. These widgets refresh themselves trough Ajax if they are enclosed in the primitive "autoRefresh". If there is no Ajax or JavaScript available, they gracefully degrade by refreshing the entire page: http://mflowdemo.herokuapp.com/noscript/combination http://haskell-web.blogspot.com.es/2013/06/and-finally-widget-auto-refreshi… The page flows and the multiflow idea was inspired in Seaside<http://www.seaside.st/>, a great Smalltalk web framework and adapted to the pure recursive nature of Haskell and the formlets. It also support some JQuery widgets integrated: modal and not modal dialogs, datePicker and other active widgets that handle other widgets. It also support the older features: persistent state, WAI, blaze-html and others integration, server process timeouts, Ajax, requirements, content management, caching of widget rendering and all the other previous stuff. I wish to thank some people for their feedback. Specially Adrian May for his feedback and interest -- Alberto.

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Call for Demo Proposals: Workshop on Functional Art, Music, Modeling and Design
by Brent Yorgey 04 Jul '13

04 Jul '13

Hi all, Below is the call for demonstration proposals for FARM 2013. Please forward to anyone who might be interested -- apologies if you receive multiple copies! Brent Yorgey publicity chair for FARM 2013 ====================================================================== FARM 2013: Call for Demo Proposals ACM SIGPLAN Workshop on Functional Art, Music, Modeling and Design Boston, Massachusetts, USA 28th September, 2013 (directly after ICFP) http://www.cis.upenn.edu/~byorgey/farm13/ ====================================================================== Do you enjoy writing beautiful code to produce beautiful artifacts? Have something cool to show off at the intersection of functional programming and visual art, music, sound, modeling, visualization, or design? FARM 2013 is seeking proposals for 10-20 minute demonstrations to be given during the workshop. For example, a demonstration could consist of a short tutorial, an exhibition of some work, or even a livecoding performance. Slots for demonstrations will be shorter than slots for accepted papers, and will not be published as part of the formal proceedings, but can be a great way to show off interesting work and get feedback from other workshop participants. A demonstration slot could be a particularly good way to get feedback on work-in-progress. Scope ----- The functional programming community is largely interested in writing beautiful programs. This workshop is intended to gather researchers and practitioners interested in writing beautiful programs that generate beautiful artifacts. Such artifacts may include visual art, music, 3D sculptures, animations, GUIs, video games, physical models, architectural models, choreographies for dance, poetry, and even physical objects such as VLSI layouts, GPU configurations, or mechanical engineering designs. The framework used need not be purely functional (“mostly functional” is fine); may be based on abstractions such as higher-order functions, monads, arrows, or streams; and may be manifested as a domain specific language or tool. Theoretical foundations, language design, implementation issues, and applications are all within the scope of the workshop. Important dates --------------- - Demonstration proposals due: Wednesday, 31 July 2013, 18:00 EDT (UTC-4) - Author notification: Monday, 5 August 2013 - Workshop: Saturday, 28 September 2013 (the day after ICFP) A demo proposal should consist of a 1 page abstract, in PDF format, explaining the proposed content of the demonstration and why it would be of interest to the attendees of FARM. Proposals will be judged on interest and relevance to the stated goals and themes of the workshop. Submissions can be made via EasyChair at https://www.easychair.org/conferences/?conf=farm2013. Organizers ---------- Workshop Chair: Paul Hudak Program Chair: Conal Elliott Publicity Chair: Brent Yorgey Program Committee ----------------- Daniel Cukier (University of São Paulo) Conal Elliott (Tabula) (chair) Kathleen Fisher (Tufts University) Richard Gabriel (IBM Research) George Giorgidze (University of Tübingen) Paul Hudak (Yale University) José Pedro Magalhães (University of Oxford) Alex McLean (University of Leeds) John Peterson (Western State Colorado University) Michael Sperber (Active Group) Henning Thielemann Brent Yorgey (University of Pennsylvania)

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Haskell Weekly News: Issue 272
by Daniel Santa Cruz 03 Jul '13

03 Jul '13

Welcome to issue 272 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers the week of June 23 to 29, 2013. Quotes of the Week * kmc: johnw: I'm rejoining this channel after months away just to tell you how incredibly wrong you are that monads are the "core concept" of Haskell * dmwit: semigroups are monoids with an identity crisis * olsner: I think doing eta something means to make it more or less pointless. But I don't recall which eta does what * mm_freak: Oleg knows what's at the end of foldr f z [1..]. * copumpkin: it's like grasping desperately for the rope of induction as you fall down the bottomless pit of coinduction Top Reddit Stories * From zero to cooperative threads in 33 lines of Haskell code Domain: haskellforall.com, Score: 78, Comments: 39 On Reddit: [1] http://goo.gl/rtkrO Original: [2] http://goo.gl/wgyAC * RSS reader written in Haskell and Ur/Web Domain: bazqux.com, Score: 66, Comments: 38 On Reddit: [3] http://goo.gl/sUw1U Original: [4] http://goo.gl/gdh5G * FP Haskell Center -- full video demo -- app development, automatic deployment, Git and GitHub integration Domain: youtube.com, Score: 64, Comments: 68 On Reddit: [5] http://goo.gl/gBi5l Original: [6] http://goo.gl/TlGL9 * Building LLVM using Shake Domain: neilmitchell.blogspot.ca, Score: 54, Comments: 6 On Reddit: [7] http://goo.gl/38rWZ Original: [8] http://goo.gl/tA5tM * Hasochism: The Pleasure and Pain of Dependently Typed Haskell Programming [pdf] Domain: personal.cis.strath.ac.uk, Score: 52, Comments: 8 On Reddit: [9] http://goo.gl/6dDsL Original: [10] http://goo.gl/ZZPZL * GHC Core by example, episode 1 - Hello Core! Domain: alpmestan.com, Score: 46, Comments: 3 On Reddit: [11] http://goo.gl/iL5ho Original: [12] http://goo.gl/mUiO5 * HPCwire: Lustre Founder Spots Haskell on HPC Horizon Domain: hpcwire.com, Score: 36, Comments: 2 On Reddit: [13] http://goo.gl/h2dmv Original: [14] http://goo.gl/1WLf8 * Adventures in Three Monads - Logic, Prompt, Failure Domain: web.mit.edu, Score: 33, Comments: 8 On Reddit: [15] http://goo.gl/JEOfw Original: [16] http://goo.gl/AI5wV * Darcs' source code is some of the cleanest Haskell I've read in a while Domain: github.com, Score: 32, Comments: 13 On Reddit: [17] http://goo.gl/TWWMh Original: [18] http://goo.gl/fZGE8 * I accidentally the entire heap: debugging Haskell programs with space leaks Domain: bitba.se, Score: 32, Comments: 6 On Reddit: [19] http://goo.gl/9Vtzy Original: [20] http://goo.gl/HCS5N * GHCJS introduction – Concurrent Haskell in the browser Domain: weblog.luite.com, Score: 30, Comments: 4 On Reddit: [21] http://goo.gl/Fk8Xd Original: [22] http://goo.gl/8CUVT * Functional Reactive Web Interfaces with GHCJS and sodium Domain: weblog.luite.com, Score: 29, Comments: 12 On Reddit: [23] http://goo.gl/5QKn0 Original: [24] http://goo.gl/VpAOv * Who Ya Gonna Call? Getting Dirty with Cmm, the GHC backend, and writing new PrimOps with Carter Schonwald (at NY-Haskell) Domain: vimeo.com, Score: 26, Comments: 14 On Reddit: [25] http://goo.gl/wUVcs Original: [26] http://goo.gl/cZaGd * "Business system" using functional programming? Domain: self.haskell, Score: 24, Comments: 44 On Reddit: [27] http://goo.gl/QcE5P Original: [28] http://goo.gl/QcE5P * The Resource Applicative Domain: haskellforall.com, Score: 23, Comments: 16 On Reddit: [29] http://goo.gl/G7TIs Original: [30] http://goo.gl/4e0Gm Top StackOverflow Questions * What's the conceptual difference between Machines and Conduits (or other similar libraries)? votes: 13, answers: 1 Read on SO: [31] http://goo.gl/hrNMl * “inject” progress logging/tracing in haskell computation? votes: 13, answers: 2 Read on SO: [32] http://goo.gl/RdEKU * Difference between free monads and fixpoints of functors? votes: 12, answers: 0 Read on SO: [33] http://goo.gl/O3oBi * Can Haskell optimize function calls the same way Clang / GCC does? votes: 12, answers: 3 Read on SO: [34] http://goo.gl/Sgf88 * Trying to figure out `random` function in Haskell votes: 10, answers: 3 Read on SO: [35] http://goo.gl/kcHsi * What does !( ) means in data constructor? votes: 9, answers: 2 Read on SO: [36] http://goo.gl/ysnNL * Anything prevents optimizing tail-recursion? votes: 9, answers: 1 Read on SO: [37] http://goo.gl/LaTY2 * Where can I find a good introduction to Haskell optimization passes? votes: 9, answers: 1 Read on SO: [38] http://goo.gl/wMYQH * Passing void * through haskell votes: 9, answers: 1 Read on SO: [39] http://goo.gl/Fiu5Q * Call main function with arguments votes: 9, answers: 2 Read on SO: [40] http://goo.gl/omwDh Until next time, [41]+Daniel Santa Cruz References 1. http://www.haskellforall.com/2013/06/from-zero-to-cooperative-threads-in-33… 2. http://www.reddit.com/r/haskell/comments/1h0wf7/from_zero_to_cooperative_th… 3. https://bazqux.com/ 4. http://www.reddit.com/r/haskell/comments/1ha5dd/rss_reader_written_in_haske… 5. http://www.youtube.com/watch?v=cyyDmQKcHMs 6. http://www.reddit.com/r/haskell/comments/1h7693/fp_haskell_center_full_vide… 7. http://neilmitchell.blogspot.ca/2013/06/building-llvm-using-shake.html 8. http://www.reddit.com/r/haskell/comments/1gxaee/building_llvm_using_shake/ 9. https://personal.cis.strath.ac.uk/conor.mcbride/pub/hasochism.pdf 10. http://www.reddit.com/r/haskell/comments/1gz03w/hasochism_the_pleasure_and_… 11. http://alpmestan.com/2013/06/27/ghc-core-by-example-episode-1/ 12. http://www.reddit.com/r/haskell/comments/1h5ml0/ghc_core_by_example_episode… 13. http://www.hpcwire.com/hpcwire/2013-06-24/lustre_founder_spots_haskell_on_h… 14. http://www.reddit.com/r/haskell/comments/1h24rv/hpcwire_lustre_founder_spot… 15. http://web.mit.edu/~ezyang/Public/threemonads.pdf 16. http://www.reddit.com/r/haskell/comments/1h1etb/adventures_in_three_monads_… 17. https://github.com/asperous/darcs_source_code 18. http://www.reddit.com/r/haskell/comments/1h4rak/darcs_source_code_is_some_o… 19. https://www.bitba.se/i-accidentally-the-entire-heap/ 20. http://www.reddit.com/r/haskell/comments/1h75fa/i_accidentally_the_entire_h… 21. http://weblog.luite.com/wordpress/?p=14&date=2013-06-03 22. http://www.reddit.com/r/haskell/comments/1h4s12/ghcjs_introduction_concurre… 23. http://weblog.luite.com/wordpress/?p=127 24. http://www.reddit.com/r/haskell/comments/1h795v/functional_reactive_web_int… 25. https://vimeo.com/69025829 26. http://www.reddit.com/r/haskell/comments/1gzmw1/who_ya_gonna_call_getting_d… 27. http://www.reddit.com/r/haskell/comments/1hb4ho/business_system_using_funct… 28. http://www.reddit.com/r/haskell/comments/1hb4ho/business_system_using_funct… 29. http://www.haskellforall.com/2013/06/the-resource-applicative.html 30. http://www.reddit.com/r/haskell/comments/1haums/the_resource_applicative/ 31. http://stackoverflow.com/questions/17281556/whats-the-conceptual-difference… 32. http://stackoverflow.com/questions/17290276/inject-progress-logging-tracing… 33. http://stackoverflow.com/questions/17307416/difference-between-free-monads-… 34. http://stackoverflow.com/questions/17344869/can-haskell-optimize-function-c… 35. http://stackoverflow.com/questions/17288614/trying-to-figure-out-random-fun… 36. http://stackoverflow.com/questions/17336774/what-does-means-in-data-constru… 37. http://stackoverflow.com/questions/17346161/anything-prevents-optimizing-ta… 38. http://stackoverflow.com/questions/17354005/where-can-i-find-a-good-introdu… 39. http://stackoverflow.com/questions/17366776/passing-void-through-haskell 40. http://stackoverflow.com/questions/17374356/call-main-function-with-argumen… 41. https://plus.google.com/105107667630152149014/about

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Liber Amicorum for Doaitse Swierstra.
by Jurriaan Hage 03 Jul '13

03 Jul '13

Dear all, Prof. Doaitse Swierstra is retiring on August 1 of this year, and is leaving the very functional programming minded Software Technology group that he has led for many decades. We have compiled a Liber Amicorum in his honour that we handed to him after his farewell speech on May 30th. You can find a download of this book at: http://www.cs.uu.nl/people/jur/liberdoaitseswierstra.pdf Not all contributions are ``technical'', and not all of them are in English, but counting up the pages, I guess about 75 percent is. best, Jurriaan Hage

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ANN: esqueleto-1.2.3
by Felipe Almeida Lessa 01 Jul '13

01 Jul '13

Hey! I'd like to announce a new version of the esqueleto package [0]. Besides SELECTs, UPDATEs, DELETEs and simple INSERTs, now esqueleto supports INSERT FROMs as well. We hope that esqueleto will be able to fulfill most of your SQL querying needs. This new feature was contributed by Sam Anklesaria [1], thanks a lot! =) Esqueleto is a bare bones, type-safe EDSL for SQL queries on persistent backends. Here's an example of what a query looks like: select $ from $ \(b, p) -> do where_ (b ^. BlogPostAuthorId ==. p ^. PersonId) orderBy [asc (b ^. BlogPostTitle)] return (b, p) Cheers, =) [0] http://hackage.haskell.org/package/esqueleto (Haddocks will be built shortly) [1] https://github.com/meteficha/esqueleto/pull/16 -- Felipe.

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