- Haskell-Cafe - Haskell.org

Either example
by Jacob Thomas 07 Feb '13

07 Feb '13

Hello I'm new to Haskell, and need help with figuring out the Either type... Any example to show how this works? Jacob

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Sol vingt simple problem in various languages and systems
by Doaitse Swierstra 07 Feb '13

07 Feb '13

At https://gist.github.com/ckirkendall/2934374 you find solutions in many languages to a simple programming problem: the evaluation of an expression in an environment. I want to point your attention to the currently last three entries: - one using the UUAGC compiler to solve the problem in an aspect oriented way (entered by Jeroen Bransen (jbransen)) - one using some Haskell features, libraries and extensions (entered by me (doaitse)) - one using our attribute grammar combinators from the AspectAG package, which expresses the various aspects in an attribute grammar style (entered by Marcos Viera (marcosomarviera)) In case you did not manage to avoid getting wound up in a discussion about programming languages you can find ammunition here. Doaitse

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GHCi (7.4.2) is working on ARM
by kenny lu 07 Feb '13

07 Feb '13

I've got a Cubieboard a few weeks back. I started it off with Linaro (Ubuntu) 12.06. Today I started to upgrade the OS to 12.11, which surprisingly came with ghc 7.4.2. And ghci magically works too. Here are the links http://www.cubieboard.org sudo apt-get install update-manager-core sudo apt-get update sudo apt-get upgrade sudo do-release-upgrade Regards, Kenny

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Haskell Weekly News: Issue 257
by Daniel Santa Cruz 07 Feb '13

07 Feb '13

Welcome to issue 257 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers the week of January 27 to February 02, 2013. Quotes of the Week * shachaf: Everyone forgets about Agda Lovelace, the first constructivist. * applicative: I have my new ghc and am reinstalling my feeble world * wuttf: My world is starting to feel like isToyLanguage x = x /= Haskell * PenguinOfDoom: Being enlightened gentlemen, we split all programming languages into two groups, sucks and doesn't-suck and put all of them into the first group. * Taneb: lens has got to be the only library with more contributors than people who know how it works * shachaf: I like to put all my application's modules under GHC.* That's because I use the GHC API, and I want them not to conflict. Top Reddit Stories * The FP Complete School of Haskell goes beta Domain: fpcomplete.com, Score: 84, Comments: 45 On Reddit: [1] http://goo.gl/dEEyU Original: [2] http://goo.gl/0eKLt * My reaction to: How To Exclude Women From Your Technical Community: A Tutorial Domain: self.haskell, Score: 75, Comments: 145 On Reddit: [3] http://goo.gl/dVnVv Original: [4] http://goo.gl/dVnVv * Edward Yang: The GHC scheduler Domain: blog.ezyang.com, Score: 72, Comments: 1 On Reddit: [5] http://goo.gl/pkCmD Original: [6] http://goo.gl/SP1s3 * GHC HEAD now has support for named holes; an extension of -XTypeHoles. Feedback welcome! Domain: github.com, Score: 44, Comments: 32 On Reddit: [7] http://goo.gl/87Pbw Original: [8] http://goo.gl/cqX9N * LiquidHaskell - Safely Catching A List By Its Tail Domain: goto.ucsd.edu, Score: 44, Comments: 2 On Reddit: [9] http://goo.gl/uxU64 Original: [10] http://goo.gl/9aS35 * ProseDoc: A literate programming tool for Haskell inspired by docco Domain: shangaslammi.github.com, Score: 43, Comments: 12 On Reddit: [11] http://goo.gl/x4YGE Original: [12] http://goo.gl/sM4bN * ANNOUNCE: GHC version 7.6.2 Domain: haskell.org, Score: 39, Comments: 16 On Reddit: [13] http://goo.gl/BS6Sm Original: [14] http://goo.gl/RPF00 * What you consider "advanced" Haskell topics? Domain: self.haskell, Score: 34, Comments: 45 On Reddit: [15] http://goo.gl/JRgzG Original: [16] http://goo.gl/JRgzG * How to write unmaintainable Haskell code Domain: github.com, Score: 34, Comments: 49 On Reddit: [17] http://goo.gl/V0nxC Original: [18] http://goo.gl/G8wNv * Introduction to Haskell, Lecture 3 is Live (Types and Typeclasses) Domain: shuklan.com, Score: 32, Comments: 5 On Reddit: [19] http://goo.gl/JyH81 Original: [20] http://goo.gl/bve7N * Proposal: A trivial Cabal package signing utility for use with Hackage Domain: github.com, Score: 32, Comments: 61 On Reddit: [21] http://goo.gl/R2l9g Original: [22] http://goo.gl/IpYSo Top StackOverflow Questions * Haskell/GHC UndecidableInstances - example for non-terminating type check? votes: 19, answers: 2 Read on SO: [23] http://goo.gl/KX8oj * Efficient parallel strategies votes: 15, answers: 2 Read on SO: [24] http://goo.gl/aDnW2 * Is it possible to implement MonadFix for `Free`? votes: 15, answers: 2 Read on SO: [25] http://goo.gl/uKOrO * Do Haskell imports have side effects? votes: 15, answers: 1 Read on SO: [26] http://goo.gl/sjltX * What monads can be expressed as Free over some functor? votes: 10, answers: 1 Read on SO: [27] http://goo.gl/Q8MF9 * What is the point of having a lazy/strict version of Writer? votes: 10, answers: 1 Read on SO: [28] http://goo.gl/InUsm * Why can applicative functors have side effects, but functors can't? votes: 9, answers: 4 Read on SO: [29] http://goo.gl/LxUi5 * How to write fixed point build rules in Shake, e.g. Latex votes: 9, answers: 1 Read on SO: [30] http://goo.gl/Ef82G * Event handling in Netwire compared to conventional FRP frameworks votes: 9, answers: 2 Read on SO: [31] http://goo.gl/mA4Kc Until next time, Daniel Santa Cruz References 1. http://fpcomplete.com/school-of-haskell-goes-beta/ 2. http://www.reddit.com/r/haskell/comments/17ngtq/the_fp_complete_school_of_h… 3. http://www.reddit.com/r/haskell/comments/17jy0e/my_reaction_to_how_to_exclu… 4. http://www.reddit.com/r/haskell/comments/17jy0e/my_reaction_to_how_to_exclu… 5. http://blog.ezyang.com/2013/01/the-ghc-scheduler/ 6. http://www.reddit.com/r/haskell/comments/17fd8c/edward_yang_the_ghc_schedul… 7. https://github.com/ghc/ghc/commit/677144b858f4a425e77399bdfbfcd43dbabd1488 8. http://www.reddit.com/r/haskell/comments/17l9xm/ghc_head_now_has_support_fo… 9. http://goto.ucsd.edu/~rjhala/liquid/haskell/blog/blog/2013/01/31/safely-cat… 10. http://www.reddit.com/r/haskell/comments/17ohbm/liquidhaskell_safely_catchi… 11. http://shangaslammi.github.com/prose-doc/ 12. http://www.reddit.com/r/haskell/comments/17keu0/prosedoc_a_literate_program… 13. http://www.haskell.org/pipermail/glasgow-haskell-users/2013-January/023661.… 14. http://www.reddit.com/r/haskell/comments/17jyw9/announce_ghc_version_762/ 15. http://www.reddit.com/r/haskell/comments/17gavl/what_you_consider_advanced_… 16. http://www.reddit.com/r/haskell/comments/17gavl/what_you_consider_advanced_… 17. https://github.com/quchen/unmaintainable_haskell/blob/master/README.md 18. http://www.reddit.com/r/haskell/comments/17idma/how_to_write_unmaintainable… 19. http://shuklan.com/haskell/lec03.html 20. http://www.reddit.com/r/haskell/comments/17ic23/introduction_to_haskell_lec… 21. https://github.com/chrisdone/cabal-sign 22. http://www.reddit.com/r/haskell/comments/17njda/proposal_a_trivial_cabal_pa… 23. http://stackoverflow.com/questions/14661073/haskell-ghc-undecidableinstance… 24. http://stackoverflow.com/questions/14624376/efficient-parallel-strategies 25. http://stackoverflow.com/questions/14636048/is-it-possible-to-implement-mon… 26. http://stackoverflow.com/questions/14666666/do-haskell-imports-have-side-ef… 27. http://stackoverflow.com/questions/14641864/what-monads-can-be-expressed-as… 28. http://stackoverflow.com/questions/14644830/what-is-the-point-of-having-a-l… 29. http://stackoverflow.com/questions/14576543/why-can-applicative-functors-ha… 30. http://stackoverflow.com/questions/14622169/how-to-write-fixed-point-build-… 31. http://stackoverflow.com/questions/14654385/event-handling-in-netwire-compa… 32. https://plus.google.com/105107667630152149014/about

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A list of Haskell-related quotes?
by Petr Pudlák 06 Feb '13

06 Feb '13

Dear haskellers, over the time I've read many funny or inspiring quotes related to Haskell, but I forgot them later. For example I vaguely remember: - "What I really like about Haskell: It's completely unlike PHP." - "To learn Haskell your brain will have to get seriously rewired." Does anybody collect them or know about such a collection? Thanks, Petr Pudlak

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Re: [Haskell-cafe] How far compilers are allowed to go with optimizations?
by Artyom Kazak 06 Feb '13

06 Feb '13

Ouch, forgot the Cafe. Would you object to this particular optimisation (replacing an algorithm with an entirely different one) if you were guaranteed that the space behaviour would not change?

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Next Meetup
by Christopher Olah 05 Feb '13

05 Feb '13

Hey All, I think we were planning on meeting on the second Wednesday of this month (Feb 13) but Hacklab has a members meeting that day. How do people feel about the 14th or 15th? Chris

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CfP: OdHac (Haskell Hackathon)
by Roman Cheplyaka 05 Feb '13

05 Feb '13

------------------------------------------------------------------------ OdHac International Haskell Hackathon May 3-5, 2013 Odessa, Ukraine http://haskell.org/haskellwiki/OdHac Co-organized with Provectus IT ------------------------------------------------------------------------ We are pleased to announce the upcoming Haskell Hackathon! The event will be held over 3 days, May 3-5, in Odessa, Ukraine. This is a great opportunity to meet your fellow haskellers in real life, find new contributors for your project, improve existing libraries and tools or even start new ones! To attend, please register at http://bit.ly/OdHacReg. Please propose projects at http://www.haskell.org/haskellwiki/OdHac/Projects Consider participating in our accommodation program: http://www.haskell.org/haskellwiki/OdHac/Accommodation

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Video! Duncan Coutts on Cloud Haskell
by Theo 05 Feb '13

05 Feb '13

Back in October 2012 Well-Typed and Haskell expert Duncan Coutts delivered a talk on 'Cloud Haskell' at the 2K12 edition of the Haskell eXchange. Cloud Haskell takes Erlang's successful approach to distributed concurrency and implements it in Haskell as a library. We will look at what this means and what possibilities it opens up. You should also get a flavour of what distributed programming in Haskell is like. The initial Cloud Haskell idea and a prototype implementation were introduced last year. Since then we have been working on a new from-scratch implementation with a focus on robustness and flexibility Watch the video on the Skills Matter website - http://bit.ly/VB9tcy

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Re: [Haskell-cafe] FFI - Approaches to C/C++
by Casey Basichis 05 Feb '13

05 Feb '13

Hi Ertugrul, I'm not entirely sure what you mean. I'm intending on using Ogre for GUI - for which there is the Hogre bindings, but after emailing the DEV about it, I didn't get the impression from his advice that I should be using it for production code. Here is what he suggested: "It depends, really. Hogre is good for running Ogre from within Haskell, but it has its limitations. The number one thing people have been struggling with is handling input with hogre - there's Hois (Haskell wrapper for OIS) but it's not perfect (it misses input events), and the other option is having to write some C++ glue. Hogre is a solid proof of concept and you can do some demos with it, but if you're e.g. writing a game it might be a bit of a struggle. In the end it's about how much you value being able to write code in Haskell (or how allergic to C++ you are)." I'm on iOS so I imagine those difficulties are compounded. I am using several other C++ libraries for which there are no existing bindings and no Haskell alternative packages that are even remotely close. Are you suggesting it would be better to write all my own FFI bindings for all the needed libraries? Everything I read suggests that Haskells strengths are in transformation and that interaction is not its strong suit. I am interested in your thoughts and I am open to whatever, but you are the first to suggest that the mix is a bad idea. Thanks, Casey >>* I'm working on a project in Haskell and C++ where the former is the*>>* brains and the latter is for UI, interaction etc.* >That's a rather odd choice. Not exactly answering your question, but >questioning your project decisions, why would you do UI and interaction >in C++? You have the necessary Haskell bindings and libraries to write >everything cleanly in Haskell. > > >Greets, >Ertugrul

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