September 2012 - Haskell

ANN: New wiki page and mailing list for combinatorics and Haskell
by Brent Yorgey 24 Sep '12

24 Sep '12

Quite a while ago there was a mailing list thread where the idea was brought up of creating a mailing list for those interested in combinatorics in the setting of Haskell. Well, I've finally gotten around to it. If you're interested in (probably extremely low-traffic) discussion and announcements relating to doing combinatorics in Haskell (computing combinatorial/ number-theoretic functions; exhaustive or random generation of combinatorial objects; type algebra; etc.), please join! http://projects.haskell.org/cgi-bin/mailman/listinfo/combinatorics There is also a wiki page for collecting information here: http://www.haskell.org/haskellwiki/Combinatorics -Brent

1 0

Haskell Weekly News: Issue 244
by Daniel Santa Cruz 20 Sep '12

20 Sep '12

Welcome to issue 244 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers the week of September 9 to September 15, 2012. Inbox As you might have heard, GHC 7.6.1 is out for all platforms. I would say "get it while it is still hot", but I guess I missed my opportunity to do that last week. [1] http://goo.gl/0fwDQ Sonke Hahn wrote in to announce that on Monday "Story Episodes of Nikki and the Robots" was was released. [2] http://goo.gl/dBifT Malcolm Wallace has uploaded videos from ICFP 2012, for those of us that didn't have the opportunity to be there. Big thanks for sharing these with the community! [3] http://goo.gl/6ZhYV Quotes of the Week * copumpkin: when in doubt, blame ski * shachaf: You can call the greengrocer and place an order. That'll convert their unordered pears into ordered pears! * shachaf: Those who would give up essential type independence for a little temporary type safety deserve neither independence nor safety. * ddarius: edwardk: So your plan for Haskell adoption is to write Haskell in languages that aren't Haskell, say "Man, these languages suck, this would be super easy in Haskell", and then use the Haskell you started with reproducing functionality at an "unbelievable" rate. * cmccann: personally I'm just waiting for an extension that demotes types to the value level, so that we can finally have natural numbers. Top Reddit Stories * Yet another Haskell IDE in the works Domain: yesodweb.com, Score: 71, Comments: 94 On Reddit: [4] http://goo.gl/N1nfs Original: [5] http://goo.gl/z47p8 * The case of the mysterious explosion in space Domain: serpentine.com, Score: 65, Comments: 9 On Reddit: [6] http://goo.gl/O782g Original: [7] http://goo.gl/eQxOc * Haskell vs. F# vs. Scala: A High-level Language Features and Parallelism Support Comparison Domain: macs.hw.ac.uk, Score: 47, Comments: 30 On Reddit: [8] http://goo.gl/XWdPX Original: [9] http://goo.gl/daRy2 * The functor design pattern Domain: haskellforall.com, Score: 42, Comments: 45 On Reddit: [10] http://goo.gl/FpJL4 Original: [11] http://goo.gl/pZ4yu * How To Exclude Women From Your Technical Community: A Tutorial Domain: tim.dreamwidth.org, Score: 42, Comments: 309 On Reddit: [12] http://goo.gl/iKN7H Original: [13] http://goo.gl/GKMjb * A simple library that allows logic programming in Haskell Domain: github.com, Score: 38, Comments: 10 On Reddit: [14] http://goo.gl/J9Pbp Original: [15] http://goo.gl/1bRw5 * Larry Wall: "You should probably know about it [Haskell] if only to be able to say 'is this like Haskell?', and, if so, then you know you'll have to hire some really smart people to program in it." Domain: youtube.com, Score: 34, Comments: 130 On Reddit: [16] http://goo.gl/z1PTW Original: [17] http://goo.gl/5bCN9 * Malcolm Wallace is broadcasting videos from ICFP Domain: m.youtube.com, Score: 33, Comments: 9 On Reddit: [18] http://goo.gl/O6uuy Original: [19] http://goo.gl/Kyg5O * Darcs hub alpha: a darcsden fork to “turn the dogfooding knobs up to 11” Domain: hub.darcs.net, Score: 30, Comments: 10 On Reddit: [20] http://goo.gl/5D614 Original: [21] http://goo.gl/pDHL9 * The Architecture of the Mighttpd High-Speed Web Server Domain: iij.ad.jp, Score: 28, Comments: 4 On Reddit: [22] http://goo.gl/7yRbw Original: [23] http://goo.gl/oCkBt * Tying the knot on a Rubik's cube Domain: self.haskell, Score: 25, Comments: 7 On Reddit: [24] http://goo.gl/0XPiY Original: [25] http://goo.gl/0XPiY * Kazu Yamamoto: Improving the performance of Warp Domain: yesodweb.com, Score: 24, Comments: 1 On Reddit: [26] http://goo.gl/yvRfR Original: [27] http://goo.gl/gEQlA * Taking advantage of "Theorems for Free"? Domain: self.haskell, Score: 20, Comments: 9 On Reddit: [28] http://goo.gl/cqy6U Original: [29] http://goo.gl/cqy6U Top StackOverflow Questions * Is there a nice way to make function signatures more informative in Haskell? votes: 37, answers: 6 Read on SO: [30] http://goo.gl/vOY98 * Purely functional data structures for text editors votes: 26, answers: 7 Read on SO: [31] http://goo.gl/ciJQ3 * Lazy Pattern matching in Data.List votes: 15, answers: 1 Read on SO: [32] http://goo.gl/T2YPC * Can I provide the type-checker with proofs about inductive naturals in GHC 7.6? votes: 14, answers: 1 Read on SO: [33] http://goo.gl/zoMDr * Why does Haskell's “flip id” has this type? votes: 12, answers: 1 Read on SO: [34] http://goo.gl/HWuyZ * How long pauses can occur in a Haskell program due to garbage collection? votes: 11, answers: 1 Read on SO: [35] http://goo.gl/Stnq7 * Good introduction to free theorems [closed] votes: 11, answers: 1 Read on SO: [36] http://goo.gl/2OVYJ * Int vs Word in common use? votes: 10, answers: 3 Read on SO: [37] http://goo.gl/JR9xK * Haskell collections with guaranteed worst-case bounds for every single operation? votes: 9, answers: 1 Read on SO: [38] http://goo.gl/Oc4L9 * Zipper data structure for graphical model editor votes: 8, answers: 1 Read on SO: [39] http://goo.gl/BF865 Until next time, Daniel Santa Cruz References 1. http://comments.gmane.org/gmane.comp.lang.haskell.general/19477 2. http://joyridelabs.de/blog/?p=1435 3. http://www.youtube.com/playlist?list=PL4UWOFngo5DV0sAM9qsfnPzNtRaDyZ7MD 4. http://www.yesodweb.com/blog/2012/09/building-haskell-ide 5. http://www.reddit.com/r/haskell/comments/zrm9z/yet_another_haskell_ide_in_t… 6. http://www.serpentine.com/blog/2012/09/12/the-case-of-the-mysterious-explos… 7. http://www.reddit.com/r/haskell/comments/zrxns/the_case_of_the_mysterious_e… 8. http://www.macs.hw.ac.uk/~dsg/gph/papers/abstracts/fhpc12.html 9. http://www.reddit.com/r/haskell/comments/zxcks/haskell_vs_f_vs_scala_a_high… 10. http://www.haskellforall.com/2012/09/the-functor-design-pattern.html 11. http://www.reddit.com/r/haskell/comments/zxl49/the_functor_design_pattern/ 12. http://tim.dreamwidth.org/1762846.html 13. http://www.reddit.com/r/haskell/comments/zxmzv/how_to_exclude_women_from_yo… 14. https://github.com/smichal/hs-logic 15. http://www.reddit.com/r/haskell/comments/zq1gb/a_simple_library_that_allows… 16. http://www.youtube.com/watch?v=LR8fQiskYII&feature=player_detailpage#t=169s 17. http://www.reddit.com/r/haskell/comments/zpff3/larry_wall_you_should_probab… 18. http://m.youtube.com/channel/UCP9g4dLR7xt6KzCYntNqYcw?&desktop_uri=%2Fchann… 19. http://www.reddit.com/r/haskell/comments/zsjag/malcolm_wallace_is_broadcast… 20. http://hub.darcs.net/ 21. http://www.reddit.com/r/haskell/comments/zx4th/darcs_hub_alpha_a_darcsden_f… 22. http://www.iij.ad.jp/en/company/development/tech/mighttpd/ 23. http://www.reddit.com/r/haskell/comments/zrydv/the_architecture_of_the_migh… 24. http://www.reddit.com/r/haskell/comments/znt85/tying_the_knot_on_a_rubiks_c… 25. http://www.reddit.com/r/haskell/comments/znt85/tying_the_knot_on_a_rubiks_c… 26. http://www.yesodweb.com/blog/2012/09/improving-warp 27. http://www.reddit.com/r/haskell/comments/ztvu7/kazu_yamamoto_improving_the_… 28. http://www.reddit.com/r/haskell/comments/zydcs/taking_advantage_of_theorems… 29. http://www.reddit.com/r/haskell/comments/zydcs/taking_advantage_of_theorems… 30. http://stackoverflow.com/questions/12416723/is-there-a-nice-way-to-make-fun… 31. http://stackoverflow.com/questions/12358083/purely-functional-data-structur… 32. http://stackoverflow.com/questions/12429449/lazy-pattern-matching-in-data-l… 33. http://stackoverflow.com/questions/12442858/can-i-provide-the-type-checker-… 34. http://stackoverflow.com/questions/12339822/why-does-haskells-flip-id-has-t… 35. http://stackoverflow.com/questions/12404031/how-long-pauses-can-occur-in-a-… 36. http://stackoverflow.com/questions/12421085/good-introduction-to-free-theor… 37. http://stackoverflow.com/questions/12432154/int-vs-word-in-common-use 38. http://stackoverflow.com/questions/12393104/haskell-collections-with-guaran… 39. http://stackoverflow.com/questions/12339805/zipper-data-structure-for-graph…

1 0

Well-Typed and Skills Matter offer Haskell courses in London in October
by Andres Löh 19 Sep '12

19 Sep '12

Dear Haskellers, Well-Typed is partnering with Skills Matter to offer two Haskell courses in London, targeting professional developers who want to learn Haskell. [If you're a Haskell expert already, but know people who might be interested in these courses, feel free to forward this mail.] Fast Track to Haskell --------------------- October 8-9 http://skillsmatter.com/course/haskell/well-typed-fast-track-to-haskell/wt-… A two-day introduction to Haskell assuming no previous Haskell or functional programming experience. Covers everything from Haskell syntax over how to define Haskell functions and datatypes up to IO and monads. Advanced Haskell ---------------- October 11-12 http://skillsmatter.com/course/haskell/well-typed-advanced-haskell/wt-4939 A two-day course for people with basic Haskell experience who want to take their Haskell skills to the next level. Covers functional data structures, profiling Haskell programs, concurrency and parallelism, programming patterns and type-level programming. The courses are designed such that they can be taken both individually and in sequence. On the day in between, October 10, Skills Matter is organizing the Haskell eXchange, a one-day conference featuring talks by Simon Peyton Jones, Simon Marlow, Lennart Augustsson, Blake Rain, Duncan Coutts and Rob Harrop. http://skillsmatter.com/event/haskell/haskell-exchange-2012 Registration for all these events is open. I hope to see many of you there. Cheers, Andres -- Andres Löh, Haskell Consultant Well-Typed LLP, http://www.well-typed.com

1 0

Descriptions of the various medications
by mmm forever 19 Sep '12

19 Sep '12

Viral diseases There are many viral diseases. Let's talk about the most common ones. Let's start with the flu virus. There are many laboratories around the world who regularly completion of stockpile vaccines and drugs to treat it. The influenza virus is most studied infectious agents. It should be noted that the epidemic virus Grip occur every year, and every few decades the epidemic of influenza is becoming a pandemic. The influenza virus has the ability to quickly change their structure. These changes affect the surface proteins - antigens, which recognizes the human immune system. Immunity of a man who developed a in contact with a variety of virus is not able to recognize the other, and when she begins her infection recognize only after full development of the disease. Antigenic variation is the ability of the virus to change its structure. It is because of her flu occur regularly. This regularity is alien to other infections, and only because of it being infected with influenza most people. Antigenic variation is of two kinds. First - antigenic drift, the second - antigenic shift. Antigenic drift - it mutations affecting two major viral proteins - hemagglutinin (H), which provides introduction of the pathogen in human cells, and neuraminidase (N), which is responsible for the output of mutated viruses from the cell. The emergence of antigenic drift is due to the fact that the enzyme, which doubles the viral RNA in the process of creating new viruses, no function of protection against errors that occur during the synthesis. These errors and lead to a mutation of the pathogen. The very same process of antigenic drift leads to a gradual change in the structure of the influenza virus, which causes it to partial or complete neuznavaniyu human immune system. It is for this reason there is a need systematically change the antigens included in the flu vaccine. Antigenic shifts - are the most significant changes in the antigenic composition of the virus. Promotes emergence antegennyh shifts that influenza can affect not only human cells, but also of animals: pigs, horses, birds, etc. In cases where the body there is more than one species of the virus, is the exchange of entire genes between viruses, thereby producing new strains of influenza, which in most cases are more aggressive than the original ones. This process and called antigenic shift. Now a wide range of antiviral drugs that you can to *buy* in our *online pharmacy <http://superpills.blogspot.com/>*. The best effect of these drugs is achieved in situations where they are beginning to use when detecting the first symptoms of influenza infection, but they are also able to facilitate the course of the disease at any stage.

1 0

ANNOUNCE: MFlow-0.1.5
by Alberto G. Corona 18 Sep '12

18 Sep '12

Hi haskellers and specially the web developers. http://hackage.haskell.org/package/MFlow-0.1.5.3 MFlow is a is a Web framework with some unique, and I mean unique, characteristics that I find exciting: - It is a Web application server that start and restart on-demand stateful web server processes (not request.-response) This means that all the page navigation can be coded in a single procedure. This increases readability of the programmer code. I woul call it a anti-node.js. Buit usual request-response (stateless) server processes are also allowed - When the process is invoqued as result of an URL request, the Web app server not only restart the process but also recover its execution state. The enclosing Workflow monad provides the thread state persistence. There are state timeouts and process timeouts defined by the programmer. Processes with no persistent state (transient) are possible. -The user interface is made of widgets. They are formlets with added formatting, attributes, validations, modifiers and callbacks, that are composable, so the pieces are reusable and return type safe responses to the calling process. Even the links are part of widgets and return back type safe inputs at compile time to the calling server process. Tho glue these components, ordinary applicative combinators and other extra combinators are used. - The widgets and the communication don´t make assumptions about the architecture, so it can be adapted to non-web environments. This versions has interface for WAI-warp, Hack, Text.XHtml (xhtml) , and Haskell Server Pages. -The widget rendering can be converted to ByteStrings automatically with special combinators. A mix of widgets with different formats can be combined in the same source file. For example Text.Html and HSP (Haskell server pages) -These widgets can be cached, to avoid widget rendering on every interaction. -To handle the back button, and because the processes are stateful, they can run backwards until the response match. This is transparent for the programmer, thanks to the embedded FlowM monad. -All the code is in pure Haskell. No deployment, special scripts, formats etc are necessary. -Besides automatic state persistence, TCache provides transactions and user data persistence, that can be configured for SQL databases. Default persistence in files permit very rapid prototyping. Just code and run it with runghc. -Has AJAX support All of this sounds very complicated, but really it is simple!. Most of these things are transparent. The resulting code is quite readable and has very little plumbing! There is a non trivial example that some of these functionalities embedded here that you can run: http://hackage.haskell.org/packages/archive/MFlow/0.1.5.3/doc/html/MFlow-Fo… Take a look and tell me your opinion. I hope that you find it as exciting as me. I´m looking for people to collaborate in the development of MFlow. Although still it is experimental, it is being used in at least one future commercial project. So I have te commitment to continue its development. There are many examples in the documentation and in the package. Alberto

1 0

(no subject)
by Clint Moore 16 Sep '12

16 Sep '12

1 0

(no subject)
by Clint Moore 16 Sep '12

16 Sep '12

1 0

[ANNOUNCE] Juicy.Pixels v2.0
by Vincent Berthoux 16 Sep '12

16 Sep '12

Hello, I'm pleased to announce the release of Juicy.Pixels (a pure Haskell library for image loading and writing) in version 2.0. The new features of this version are a Gif file decoder, and a rework of the plane extraction part to be type safe github: https://github.com/Twinside/Juicy.Pixels hackage: http://hackage.haskell.org/package/JuicyPixels Thanks Vincent Berthoux

1 0

ANNOUNCE: adt.js (Algebraic Data Types, JavaScript library)
by code＠rehno.lindeque.name 15 Sep '12

15 Sep '12

Hi all, I'm pleased to give you adt.js - algebraic data types for JavaScript. * https://github.com/rehno-lindeque/adt.js (The source code & README) * https://groups.google.com/forum/#!forum/adtjs (A place to chat) adt.js is an unusual take on algebraic data types for JavaScript, that may be useful to Haskell web developers. Specifically, the adt.js serializer/deserializer attempts to imitate Haskell's default (deriving) Show and Read implementations for common data types. This allows you to pass data values between server-side Haskell and browser-side JavaScript with ease (simply apply show/read in Haskell and adt.serialize/adt.deserialize in JavaScript). It differs from other attempts in that it embraces JavaScript's built-in types in its interfaces and makes a few less obvious design choices (illustrated by examples in the README). This is more of a "I coded this and I'm finding it useful" announcement than an official release (or 0.0, if you will). Before making an official release, the idea is to dice up the library into multiple versions - each of which will be progressively more heavy-weight and implement more advanced features from the library. I haven't had time to implement such an advanced build system, however I'm already using the library for some relatively serious projects to be put into production at a later date. There's also a few related libraries I'm working on (however, fair warning, documentation is really not great right now): https://github.com/rehno-lindeque/adt-html.js (HTML should have been an ADT) https://github.com/rehno-lindeque/adt-typecheck.js (Type check JS objects) I'm a little time constrained in terms of answering questions etc (which I deeply regret), however I welcome contributors and will gladly accept/moderate pull requests. Suggestions and feedback are more than welcome, I realize that there's still many possible improvements to be made. Thank you for your attention! Kind regards, Rehno

1 0

ANN: hub.darcs.net
by Simon Michael 15 Sep '12

15 Sep '12

Hello darcs fans, I'm pleased to announce http://hub.darcs.net ! This is a new darcs repository hosting site, where you can: - publish public and private darcs repos under your user account - push/pull changes with darcs over SSH - browse repos, files and changes - fork repos - view and merge changes from upstream and downstream repos - track issues It is running Alex Suraci's darcsden software, updated by myself and others (see darcsden 1.0 announcement.) The site has been in alpha test by #darcs folks for some time. Now I'd like to invite the wider Darcs and Haskell community to bang on it. Please try it out and report problems! All kinds of darcs repository are welcome, but if I see anything too large for the current hosting setup I'll let you know. You can expect occasional bugs or performance issues, but not data loss. As with all cloud-based services, always keep a copy of your data elsewhere. For more details, including how to help, see http://hub.darcs.net . We hope to see you on #darcs and on the hub. Best, -Simon and the Darcs team

1 0