- Haskell-Cafe - Haskell.org

Re: [Haskell-cafe] [GSoC 2013] Porting Charts to Diagrams - Final Report
by Daniel Santa Cruz 26 Sep '13

26 Sep '13

Awesome work, Jan. I'm looking forward to playing around with the new libs! As a side note, what did you use to generate your email? Did you manage all the footnotes by hand? Daniel

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Haskell Job Opportunity (Remote Work)
by Benny 26 Sep '13

26 Sep '13

Hello, ShotVibe is an early-stage Israeli startup company in the mobile photo sharing space. We are looking for an experienced or expert level Haskell programmer for backend web related projects. The work will be done by you remotely, using a freelancer model, with the potential for longer term work in the near future (also remote). One of the projects we have is a server application that queues messages that are to be sent to end user mobile phones, and pushes them through the "push notification" APIs supplied by Google and Apple. The work needed here involves some bug fixes, and some new features. This project will likely eventually be open sourced. Another project that we need to be written from scratch is a web application that handles photo uploads and processes them (including verifying user authentication with our main web backend, image resizing, and storing images on Amazon S3). This will probably end up only a few hundred lines of Haskell code, but involves integrating a bunch of stuff together. We are also interested in experimenting in using Haskell for some other areas of our backend where we are currently using Python. If you are interested you may contact me at: benny(a)shotvibe.com Please feel free to forward this email to any friends or acquaintances that may be interested.

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Haskell Weekly News: Issue 281
by Daniel Santa Cruz 26 Sep '13

26 Sep '13

Welcome to issue 281 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers the week of September 15 to 21, 2013. Quotes of the Week * jmcarthur: weak algebraic structures? ha! i prefer my algebraic structures to put up more of a fight. * newsham: teach a man to pred and he will pred to zero. teach a man to succ and he will succ forever Top Reddit Stories * Edward C++Hands Domain: bartoszmilewski.com, Score: 83, Comments: 102 On Reddit: [1] http://goo.gl/64LLo4 Original: [2] http://goo.gl/0H0yr7 * Perfect streaming using `pipes-bytestring` Domain: haskellforall.com, Score: 59, Comments: 45 On Reddit: [3] http://goo.gl/oSlzZP Original: [4] http://goo.gl/8xwZjc * Adding safe coercions to Haskell Domain: joachim-breitner.de, Score: 58, Comments: 23 On Reddit: [5] http://goo.gl/2vs5M9 Original: [6] http://goo.gl/n0RYA3 * Which programming languages do you like besides Haskell, and why? Domain: self.haskell, Score: 55, Comments: 104 On Reddit: [7] http://goo.gl/nzgwJQ Original: [8] http://goo.gl/nzgwJQ * GHC HEAD: merged checkable "minimal complete definitions" (#7633) Domain: ghc.haskell.org, Score: 48, Comments: 36 On Reddit: [9] http://goo.gl/VoZVYL Original: [10] http://goo.gl/5F61AX * Do companies ever hire someone who has no Haskell experience to be a Haskell programmer? If I pursue such a job, how important would a Domain: self.haskell, Score: 44, Comments: 50 On Reddit: [11] http://goo.gl/KA998k Original: [12] http://goo.gl/KA998k * [Haskell-cafe] PSA: do not install xcode 5 if you are using ghc 7.6 Domain: haskell.org, Score: 43, Comments: 4 On Reddit: [13] http://goo.gl/ut6k6p Original: [14] http://goo.gl/1G8Syo * Model Analysis - The New York Times’ Erik Hinton breaks down a Fashion Week special Domain: source.mozillaopennews.org, Score: 40, Comments: 4 On Reddit: [15] http://goo.gl/NdVw6l Original: [16] http://goo.gl/bYB8JS * Programming reactively with both barrels (experiences of Haskell/FRP for mobile games) Domain: blog.reactiveprogramming.org, Score: 39, Comments: 7 On Reddit: [17] http://goo.gl/QXacUo Original: [18] http://goo.gl/wLJwt6 * Why monads have not taken the Common Lisp world by storm [r/lisp] Domain: reddit.com, Score: 33, Comments: 14 On Reddit: [19] http://goo.gl/tZUVWx Original: [20] http://goo.gl/w5KHqc * 13,000 readers Domain: self.haskell, Score: 28, Comments: 11 On Reddit: [21] http://goo.gl/lTys0R Original: [22] http://goo.gl/lTys0R * A type for IO actions that do not throw exceptions Domain: self.haskell, Score: 25, Comments: 49 On Reddit: [23] http://goo.gl/Ao8HyB Original: [24] http://goo.gl/Ao8HyB * ANN: Scotty 0.5.0 Released Domain: github.com, Score: 24, Comments: 15 On Reddit: [25] http://goo.gl/jgGJhO Original: [26] http://goo.gl/BejPTF * Haskell version freezing Domain: blog.docmunch.com, Score: 23, Comments: 8 On Reddit: [27] http://goo.gl/9LJSjY Original: [28] http://goo.gl/Ikd86k * PHOAS For Free by Edward Kmett Domain: fpcomplete.com, Score: 21, Comments: 8 On Reddit: [29] http://goo.gl/RDt1BV Original: [30] http://goo.gl/o0phN7 * Cellular Automata, Part III by Edward Kmett Domain: fpcomplete.com, Score: 20, Comments: 0 On Reddit: [31] http://goo.gl/AKCfGw Original: [32] http://goo.gl/x7GtH1 * Translating Haskell programs to Coq [/Gallina] programs Domain: github.com, Score: 20, Comments: 2 On Reddit: [33] http://goo.gl/IQAp3K Original: [34] http://goo.gl/qcib77 * ANN: pipes-csv: a fast, streaming csv parser based on cassava and pipes Domain: github.com, Score: 20, Comments: 9 On Reddit: [35] http://goo.gl/aITtGX Original: [36] http://goo.gl/yrzZ7n Top StackOverflow Questions * What does the “Just” syntax mean in Haskell? votes: 12, answers: 4 Read on SO: [37] http://goo.gl/f17UEP * How can I understand “:t ((==) <*>)” in haskell? votes: 10, answers: 1 Read on SO: [38] http://goo.gl/CwyBn4 * why polymorphism is so costly in haskell(GHC)? votes: 10, answers: 3 Read on SO: [39] http://goo.gl/4MjcbH * Break and continue in GHCi debugger without use of breakpoints votes: 9, answers: 0 Read on SO: [40] http://goo.gl/HrtcXZ * Why is there no `-XDeriveApplicative` extension? votes: 8, answers: 1 Read on SO: [41] http://goo.gl/4dcRF1 * Downsides to ScopedTypeVariables votes: 7, answers: 2 Read on SO: [42] http://goo.gl/UjBcsg * Haskell design encompassing several monads votes: 7, answers: 1 Read on SO: [43] http://goo.gl/EwWd5d * How to correct my OOP tendencies when programming in Haksell votes: 7, answers: 3 Read on SO: [44] http://goo.gl/9JVqh7 * composing functions with higher arity votes: 7, answers: 5 Read on SO: [45] http://goo.gl/jQjNJW * Why are Haskell Maps implemented as balanced binary trees instead of traditional hashtables? votes: 7, answers: 3 Read on SO: [46] http://goo.gl/nZaLGV Until next time, [47]+Daniel Santa Cruz References 1. http://bartoszmilewski.com/2013/09/19/edward-chands/ 2. http://www.reddit.com/r/haskell/comments/1mqni1/edward_chands/ 3. http://www.haskellforall.com/2013/09/perfect-streaming-using-pipes-bytestri… 4. http://www.reddit.com/r/haskell/comments/1msinm/perfect_streaming_using_pip… 5. http://www.joachim-breitner.de/blog/archives/610-Adding-safe-coercions-to-H… 6. http://www.reddit.com/r/haskell/comments/1mfz8z/adding_safe_coercions_to_ha… 7. http://www.reddit.com/r/haskell/comments/1mvb2e/which_programming_languages… 8. http://www.reddit.com/r/haskell/comments/1mvb2e/which_programming_languages… 9. http://ghc.haskell.org/trac/ghc/ticket/7633#comment:28 10. http://www.reddit.com/r/haskell/comments/1mp434/ghc_head_merged_checkable_m… 11. http://www.reddit.com/r/haskell/comments/1mtcox/do_companies_ever_hire_some… 12. http://www.reddit.com/r/haskell/comments/1mtcox/do_companies_ever_hire_some… 13. http://www.haskell.org/pipermail/haskell-cafe/2013-September/108902.html 14. http://www.reddit.com/r/haskell/comments/1ml97r/haskellcafe_psa_do_not_inst… 15. http://source.mozillaopennews.org/en-US/learning/model-analysis/ 16. http://www.reddit.com/r/haskell/comments/1mlgwd/model_analysis_the_new_york… 17. http://blog.reactiveprogramming.org/?p=107 18. http://www.reddit.com/r/haskell/comments/1moob5/programming_reactively_with… 19. http://www.reddit.com/r/lisp/comments/1mkqvj/why_monads_have_not_taken_the_… 20. http://www.reddit.com/r/haskell/comments/1mn6vb/why_monads_have_not_taken_t… 21. http://www.reddit.com/r/haskell/comments/1modra/13000_readers/ 22. http://www.reddit.com/r/haskell/comments/1modra/13000_readers/ 23. http://www.reddit.com/r/haskell/comments/1mpsvj/a_type_for_io_actions_that_… 24. http://www.reddit.com/r/haskell/comments/1mpsvj/a_type_for_io_actions_that_… 25. https://github.com/xich/scotty/blob/master/ReleaseNotes.md 26. http://www.reddit.com/r/haskell/comments/1mr9hf/ann_scotty_050_released/ 27. http://blog.docmunch.com/blog/2013/haskell-version-freezing 28. http://www.reddit.com/r/haskell/comments/1mjldi/haskell_version_freezing/ 29. https://www.fpcomplete.com/user/edwardk/phoas 30. http://www.reddit.com/r/haskell/comments/1mo59h/phoas_for_free_by_edward_km… 31. https://www.fpcomplete.com/user/edwardk/cellular-automata/part-3 32. http://www.reddit.com/r/haskell/comments/1mfaqx/cellular_automata_part_iii_… 33. https://github.com/gdijkstra/hs-to-gallina/blob/master/docs/report/report.p… 34. http://www.reddit.com/r/haskell/comments/1miawm/translating_haskell_program… 35. https://github.com/jb55/pipes-csv 36. http://www.reddit.com/r/haskell/comments/1mvbk7/ann_pipescsv_a_fast_streami… 37. http://stackoverflow.com/questions/18808258/what-does-the-just-syntax-mean-… 38. http://stackoverflow.com/questions/18813431/how-can-i-understand-t-in-haske… 39. http://stackoverflow.com/questions/18854866/why-polymorphism-is-so-costly-i… 40. http://stackoverflow.com/questions/18876128/break-and-continue-in-ghci-debu… 41. http://stackoverflow.com/questions/18861231/why-is-there-no-xderiveapplicat… 42. http://stackoverflow.com/questions/18852341/downsides-to-scopedtypevariables 43. http://stackoverflow.com/questions/18866558/haskell-design-encompassing-sev… 44. http://stackoverflow.com/questions/18867620/how-to-correct-my-oop-tendencie… 45. http://stackoverflow.com/questions/18905867/composing-functions-with-higher… 46. http://stackoverflow.com/questions/18908639/why-are-haskell-maps-implemente… 47. https://plus.google.com/105107667630152149014/about

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Haskell Weekly News: Issue 280
by Daniel Santa Cruz 25 Sep '13

25 Sep '13

Welcome to issue 280 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers the week of September 8 to 14, 2013. Quotes of the Week * haasn: edwardk uses things in anger. shachaf uses them with disappointment :( * shachaf: Are you reading Mac Lane now? Saizan: yeah, it's not so bad if you skip the examples Top Reddit Stories * For my 17th birthday, my best friend got me "The most obscure programming book I could find" as a joke. I know what language I am learning next! Domain: i.imgur.com, Score: 163, Comments: 67 On Reddit: [1] http://goo.gl/0SyN5l Original: [2] http://goo.gl/oqGBzL * pipes-4.0: Simpler types and API Domain: haskellforall.com, Score: 95, Comments: 36 On Reddit: [3] http://goo.gl/ciVnq5 Original: [4] http://goo.gl/g9oq3i * Hackage 2 now available for beta testing -- switchover in a few weeks Domain: beta.hackage.haskell.org, Score: 91, Comments: 17 On Reddit: [5] http://goo.gl/aIhL67 Original: [6] http://goo.gl/zfprr9 * Cartesian Closed Comic #22: Cabal 1.18 Domain: ro-che.info, Score: 90, Comments: 3 On Reddit: [7] http://goo.gl/tVUUFG Original: [8] http://goo.gl/O0BR6c * Parallel and Incremental CRCs by Edward Kmett Domain: fpcomplete.com, Score: 58, Comments: 7 On Reddit: [9] http://goo.gl/YAChJl Original: [10] http://goo.gl/WnMsbY * Conquering Folds by Edward Kmett Domain: fpcomplete.com, Score: 47, Comments: 42 On Reddit: [11] http://goo.gl/reAjgu Original: [12] http://goo.gl/kHsSye * Conal Elliot: From Haskell to hardware via cartesian closed categories Domain: conal.net, Score: 47, Comments: 3 On Reddit: [13] http://goo.gl/VCwp7Y Original: [14] http://goo.gl/NO1sbs * FP Complete to release a personal edition of their online IDE Domain: fpcomplete.com, Score: 39, Comments: 38 On Reddit: [15] http://goo.gl/QOMy5Y Original: [16] http://goo.gl/XBE7zT * Quark : A Web Browser with a Formally Verified Kernel Domain: goto.ucsd.edu, Score: 36, Comments: 6 On Reddit: [17] http://goo.gl/RDZMY0 Original: [18] http://goo.gl/rgBcki * My first Haskell program - FNIStash - a utility for Torchlight 2 using threepenny for the GUI Domain: fluffynukeit.com, Score: 36, Comments: 19 On Reddit: [19] http://goo.gl/cK2N8v Original: [20] http://goo.gl/XOMTgQ * Conal Elliott: Overloading lambda Domain: conal.net, Score: 34, Comments: 4 On Reddit: [21] http://goo.gl/fQTt1P Original: [22] http://goo.gl/oPSQ3R * Cost semantics for STG in modern GHC Domain: blog.ezyang.com, Score: 31, Comments: 5 On Reddit: [23] http://goo.gl/mIQQxm Original: [24] http://goo.gl/5Sa49T * 0install - Python vs. OCaml vs. Haskell Domain: roscidus.com, Score: 31, Comments: 23 On Reddit: [25] http://goo.gl/htCf1x Original: [26] http://goo.gl/zhrVp0 * LogicGrowsOnTrees: a parallel implementation of logic programming using distributed tree exploration Domain: github.com, Score: 31, Comments: 9 On Reddit: [27] http://goo.gl/zp5lou Original: [28] http://goo.gl/5BgYh2 * RSS reader made by Haskell running on mbed platform (RAM size 64kB, using Ajhc Haskell compiler). Domain: youtube.com, Score: 30, Comments: 5 On Reddit: [29] http://goo.gl/n0Gkan Original: [30] http://goo.gl/cwL4vP * Conal Elliott: Optimizing CCCs Domain: conal.net, Score: 30, Comments: 12 On Reddit: [31] http://goo.gl/HVv8dr Original: [32] http://goo.gl/MCn0sO * Snap (and Heist) 0.13 released Domain: snapframework.com, Score: 29, Comments: 7 On Reddit: [33] http://goo.gl/zW5Sdn Original: [34] http://goo.gl/1wSLeJ * ANN: threepenny-gui-0.3 – GUI framework that uses the web browser as a display – now with FRP built-in Domain: apfelmus.nfshost.com, Score: 28, Comments: 8 On Reddit: [35] http://goo.gl/RUDrKD Original: [36] http://goo.gl/WZMeZN Top StackOverflow Questions * In Haskell, where does the range ['a'..] stop? votes: 20, answers: 2 Read on SO: [37] http://goo.gl/Oms7lr * Why were Haskell 98's standard classes made inferior to Haskell 1.3's? votes: 18, answers: 1 Read on SO: [38] http://goo.gl/WxvdL2 * 27 different Bool to Bool values in Haskell votes: 14, answers: 1 Read on SO: [39] http://goo.gl/1PcD1g * How to reconstruct Haskell expression from type votes: 10, answers: 1 Read on SO: [40] http://goo.gl/Qx06kz * Can links to anchors in haddock be labeled? votes: 8, answers: 0 Read on SO: [41] http://goo.gl/5deOMM * How to convert between ByteString and Storable Vector? votes: 7, answers: 1 Read on SO: [42] http://goo.gl/zBVVzI * Why is not GHC optimizing for constants? votes: 7, answers: 2 Read on SO: [43] http://goo.gl/sfo64S * newtype around ST causes type error votes: 7, answers: 1 Read on SO: [44] http://goo.gl/CwXaJp * GHC does not generate a binary despite no errors shown votes: 6, answers: 1 Read on SO: [45] http://goo.gl/PAv1oQ Until next time, [46]+Daniel Santa Cruz References

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Mystery of an Eq instance
by damodar kulkarni 24 Sep '13

24 Sep '13

Hello, There were some recent discussions on the floating point support in Haskell and some not-so-pleasant "surprises" people encountered. There is an Eq instance defined for these types! So I tried this: *Main> sqrt (10.0) ==3.1622776601683795 True *Main> sqrt (10.0) ==3.16227766016837956 True *Main> sqrt (10.0) ==3.1622776601683795643 True *Main> sqrt (10.0) ==3.16227766016837956435443343 True It seems strange. So my doubts are: 1. I wonder how the Eq instance is defined in case of floating point types in Haskell? 2. Can the Eq instance for floating point types be considered "meaningful"? If yes, how? In general, programmers are **advised** not to base conditional branching on tests for **equality** of two floating point values. 3. Is this particular behaviour GHC specific? (I am using GHC 6.12.1) If there are references on this please share. Thanks and regards, -Damodar Kulkarni

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Hackathon der Frankfurt-Haskell-User-Group
by Peter Althainz 24 Sep '13

24 Sep '13

the Frankfurt Haskell User Group announces its first Hackathon, if interested, see here: http://www.meetup.com/Frankfurt-Haskell-User-Group/events/138895112/ Peter Althainz

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Strange exit status behavior from the process package
by Michael Xavier 23 Sep '13

23 Sep '13

I've run into some strangeness with the process package. When you kill some processes on the command line you correctly get a non-zero exit status. However when using the process package's terminateProcess (which sends a SIGTERM), it returns an ExitSuccess: module Main (main) where import Control.Concurrent (threadDelay) import System.Process (createProcess, proc, getProcessExitCode, terminateProcess) main :: IO () main = do (_, _, _, ph) <- createProcess $ proc "/usr/bin/sleep" ["100"] terminateProcess ph threadDelay 1000000 print =<< getProcessExitCode ph -- prints Just ExitSuccess, should be Just (ExitFailure 143) term1: sleep 100 term2: pkill sleep term1: echo $? # 143 Anyone know what might be going on? -- Michael Xavier http://www.michaelxavier.net

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Creating a local Hoogle ...
by aditya siram 23 Sep '13

23 Sep '13

Hi all, I've installed Hoogle but am having issues creating the databases. I first did: `hoogle data all`, tried a search `hoogle "[a] -> a" and got: Could not find some databases: default Searching in: . ~/.cabal/share/hoogle-4.2.21/databases Either the package does not exist or has not been generated Found 4263 databases, including: abacate abcnotation abortt-monadstf abortt-mtl abortt-transformers So to create th default database I did: `hoogle combine *.hoo` and then got: Combining 4263 databases hoogle: embroidery.hoo: openFile: resource exhausted (Too many open files) Any help is appreciated. Thanks! -deech

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Embedding compiled Haskell Platform in custom application
by blackbox.dev.ml 23 Sep '13

23 Sep '13

Hi! I'm writing a tool that generates haskell code, build it with cabal and launch it. I want to deliver that tool to clients, but I don't want to force them, to install system wide any specific ghc or cabal version. How can I embed compiled ghc, cabal and selected libraries (for specific platform) in installer of my application?

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PSA: do not install xcode 5 if you are using ghc 7.6
by Carter Schonwald 23 Sep '13

23 Sep '13

Hey everyone, if you are actively using ghc 7.6 on your mac, for now please do not install xcode 5. It will break your ghc install, because 7.6 doesn't know how to correctly use Clang for the CPP work. (ghc head / and thus 7.8 will work fine with xcode 5, thanks to some outstanding work by Austin Seipp, 7.6 does not) if you do not need xcode 5, and you're actively using ghc 7.6, stay with xcode 4.6 for now. if you installed xcode 5 because its there, and now your ghc 7.6 is occasionally giving you strange errors involving CPP parse failures on fragments like "#-}", you should go to the apple developers website, download, and reinstall the xcode 4.6 CLI tools. if you need both xcode 5 and ghc in working order *right now, tomorrow*, either a) live on the wildside: test out using ghc head: also means you could play with ghc-ios too! b) if you need both in working order now, and stabilish, Darin Morrison has a set of mac-homebrew taps that should be you use https://github.com/darinmorrison/homebrew-haskell these taps should be regarded as more "official" and "canonical" than the formula's that brew provides (the normal brew ones recurrently have problems induced by folks who aren't haskell devs) c) wait a wee bit till 7.8 lands in all its glory, and have both the freshest of xcodes, and the newest of awesome ghcs tl;dr if you don't need xcode 5, having xcode 4.6 CLI tools installed will stand you in good stead. if you are on os x mavericks, or absolutely need xcode 5 installed, and you want a ghc thats already released, use darin's brew formulae https://github.com/darinmorrison/homebrew-haskell Darin and I plan to spend some time next month preparing an unofficial patched version of ghc 7.6 that should play nice with clang / xcode 5, though at such a time ghc 7.8 will be in RC status at the very least. cheers -Carter

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