Welcome to issue 255 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers the weeks of January 06 to 19, 201. Quotes of the Week * ky3: Indexed monads are just categories in the category of endofunctors, what's the problem? * tac: I guess I'm just living in a fantasy world where the docs tell you how to use such a basic API :P * shachaf: 3.0 is an edwardk phase, not just a version number. It's like Picasso's Blue Period. * cmccann: Clearly the reason why edwardk uses Haskell now is because every C++ compiler has a restraining order against him. * shachaf: I'm not sure what your question is, but maybe lens is the answer. * cmccann: * cmccann has concluded that lenses are just a category whose objects are english prepositions and whose morphisms are all unsafeCoerce * shachaf: Some people, when asking about a problem in #haskell, get a link to okmij.org. Now they have two problems. * quicksilver: It returns undefined for convenience. I'm not really sure it's that convenient, but that's why. * edwardk: cmccann: let me get this straight you are saying that someone [mm_freak] who by their very nick admits to being a freak did something freakish? Top Reddit Stories * LiquidHaskell: Refinement Types in Haskell via SMT Domain: goto.ucsd.edu, Score: 71, Comments: 22 On Reddit: [1] http://goo.gl/PE2nf Original: [2] http://goo.gl/P3Gm9 * Hakyll 4.0 released Domain: jaspervdj.be, Score: 59, Comments: 19 On Reddit: [3] http://goo.gl/IQAXq Original: [4] http://goo.gl/AbLnM * When Haskell is faster than C Domain: paulspontifications.blogspot.co.uk, Score: 52, Comments: 23 On Reddit: [5] http://goo.gl/3rj8J Original: [6] http://goo.gl/N2cbA * I'm teaching an introductory 12-week class on Haskell. Join in for a journey! Domain: reddit.com, Score: 45, Comments: 15 On Reddit: [7] http://goo.gl/TsnQ5 Original: [8] http://goo.gl/EMMVR * Subtractable values are torsors Domain: ro-che.info, Score: 42, Comments: 15 On Reddit: [9] http://goo.gl/4IcMp Original: [10] http://goo.gl/6YJrY * Chordify: extract chord sequences from MP3's using HarmTrace Domain: chordify.net, Score: 42, Comments: 8 On Reddit: [11] http://goo.gl/8J7rA Original: [12] http://goo.gl/ySfR5 * Getting Started with Haskell Domain: bob.ippoli.to, Score: 41, Comments: 8 On Reddit: [13] http://goo.gl/4Evnb Original: [14] http://goo.gl/nzg9o * Using AngularJS with Haskell Snap Domain: nurpax.github.com, Score: 40, Comments: 19 On Reddit: [15] http://goo.gl/SH8e1 Original: [16] http://goo.gl/0lSyN * Down with kinds: adding dependent heterogeneous equality to to FC Domain: cis.upenn.edu, Score: 38, Comments: 14 On Reddit: [17] http://goo.gl/iEvyI Original: [18] http://goo.gl/cH0Eo * Fixing GADTs : Generic recursion schemes for GADTs using fixed points of higher-order functors Domain: timphilipwilliams.com, Score: 38, Comments: 25 On Reddit: [19] http://goo.gl/dEMq9 Original: [20] http://goo.gl/vnjhp * What's the importance of Category Theory in Haskell? Is it worth really studying? Domain: self.haskell, Score: 37, Comments: 60 On Reddit: [21] http://goo.gl/T430r Original: [22] http://goo.gl/T430r * Parsing Markdown with Parsec: How Pandoc does it Domain: youtube.com, Score: 35, Comments: 13 On Reddit: [23] http://goo.gl/TN9TJ Original: [24] http://goo.gl/zpX7f * Clckwrks, from the creator of Happstack, is developing into a clean alternative to Wordpress Domain: clckwrks.com, Score: 34, Comments: 7 On Reddit: [25] http://goo.gl/L9WXx Original: [26] http://goo.gl/FZRpU * pipes-safe-1.0 - Resource management and exception handling for pipes Domain: haskellforall.com, Score: 32, Comments: 27 On Reddit: [27] http://goo.gl/HeLWz Original: [28] http://goo.gl/1hTFc Top StackOverflow Questions * values, types, kinds,… as an infinite sequence? votes: 36, answers: 1 Read on SO: [29] http://goo.gl/lyyYc * Why is this a useful warning in Haskell when pattern matching? “Defined but not used” votes: 17, answers: 3 Read on SO: [30] http://goo.gl/iQLFq * Why are getArgs and getProgName IO actions? votes: 16, answers: 3 Read on SO: [31] http://goo.gl/5ZPYO * Can GADTs be used to prove type inequalities in GHC? [duplicate] votes: 14, answers: 2 Read on SO: [32] http://goo.gl/fDdha * Applying Denotational Semantics to design of Programs [migrated] votes: 14, answers: 0 Read on SO: [33] http://goo.gl/KLOCX * Examples where compiler-optimized functional code performs better than imperative code votes: 14, answers: 1 Read on SO: [34] http://goo.gl/Fzqdx * Why is there only one non-strict function from Int to Int? votes: 12, answers: 2 Read on SO: [35] http://goo.gl/KXcAy * Dependency injection in Haskell: solving the task idiomatically votes: 12, answers: 3 Read on SO: [36] http://goo.gl/xTcYc * What does a Haskell comment starting with `{- |` generally mean? votes: 11, answers: 1 Read on SO: [37] http://goo.gl/zNikw * Is operational really isomorphic to a free monad? votes: 10, answers: 3 Read on SO: [38] http://goo.gl/AJlgH Until next time, [39]+Daniel Santa Cruz References 1. http://goto.ucsd.edu/~rjhala/liquid/haskell/blog/blog/2013/01/01/refinement-... 2. http://www.reddit.com/r/haskell/comments/16w3hp/liquidhaskell_refinement_typ... 3. http://jaspervdj.be/posts/2013-01-16-hakyll-4.0.html 4. http://www.reddit.com/r/haskell/comments/16ojtv/hakyll_40_released/ 5. http://paulspontifications.blogspot.co.uk/2013/01/when-haskell-is-faster-tha... 6. http://www.reddit.com/r/haskell/comments/16tryo/when_haskell_is_faster_than_... 7. http://www.reddit.com/r/UniversityofReddit/comments/169jfe/class_introductio... 8. http://www.reddit.com/r/haskell/comments/169k67/im_teaching_an_introductory_... 9. http://ro-che.info/articles/2013-01-08-torsors.html 10. http://www.reddit.com/r/haskell/comments/166iju/subtractable_values_are_tors... 11. http://chordify.net/pages/how-to-use-chordify/ 12. http://www.reddit.com/r/haskell/comments/16u44u/chordify_extract_chord_seque... 13. http://bob.ippoli.to/archives/2013/01/11/getting-started-with-haskell/ 14. http://www.reddit.com/r/haskell/comments/16fegr/getting_started_with_haskell... 15. http://nurpax.github.com/posts/2013-01-13-angularjs-and-haskell.html 16. http://www.reddit.com/r/haskell/comments/16iaiq/using_angularjs_with_haskell... 17. http://www.cis.upenn.edu/~eir/papers/2013/jmnokinds/jmnokinds.pdf 18. http://www.reddit.com/r/haskell/comments/167c21/down_with_kinds_adding_depen... 19. http://www.timphilipwilliams.com/posts/2013-01-16-fixing-gadts.html 20. http://www.reddit.com/r/haskell/comments/16qr6q/fixing_gadts_generic_recursi... 21. http://www.reddit.com/r/haskell/comments/16i322/whats_the_importance_of_cate... 22. http://www.reddit.com/r/haskell/comments/16i322/whats_the_importance_of_cate... 23. http://www.youtube.com/watch?v=nCwG9ijQMuQ&t=01m22s 24. http://www.reddit.com/r/haskell/comments/16kf0j/parsing_markdown_with_parsec... 25. http://www.clckwrks.com/ 26. http://www.reddit.com/r/haskell/comments/168j2w/clckwrks_from_the_creator_of... 27. http://www.haskellforall.com/2013/01/pipes-safe-10-resource-management-and.h... 28. http://www.reddit.com/r/haskell/comments/16mban/pipessafe10_resource_managem... 29. http://stackoverflow.com/questions/14401689/values-types-kinds-as-an-infinit... 30. http://stackoverflow.com/questions/14309396/why-is-this-a-useful-warning-in-... 31. http://stackoverflow.com/questions/14295582/why-are-getargs-and-getprogname-... 32. http://stackoverflow.com/questions/14273235/can-gadts-be-used-to-prove-type-... 33. http://stackoverflow.com/questions/14349232/applying-denotational-semantics-... 34. http://stackoverflow.com/questions/14357918/examples-where-compiler-optimize... 35. http://stackoverflow.com/questions/14262014/why-is-there-only-one-non-strict... 36. http://stackoverflow.com/questions/14327327/dependency-injection-in-haskell-... 37. http://stackoverflow.com/questions/14270500/what-does-a-haskell-comment-star... 38. http://stackoverflow.com/questions/14263363/is-operational-really-isomorphic... 39. https://plus.google.com/105107667630152149014/about