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 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-types-101.lhs/

2. http://www.reddit.com/r/haskell/comments/16w3hp/liquidhaskell_refinement_types_in_haskell_via_smt/

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-than-c.html

6. http://www.reddit.com/r/haskell/comments/16tryo/when_haskell_is_faster_than_c/

7. http://www.reddit.com/r/UniversityofReddit/comments/169jfe/class_introduction_to_haskell/

8. http://www.reddit.com/r/haskell/comments/169k67/im_teaching_an_introductory_12week_class_on/

9. http://ro-che.info/articles/2013-01-08-torsors.html

10. http://www.reddit.com/r/haskell/comments/166iju/subtractable_values_are_torsors/

11. http://chordify.net/pages/how-to-use-chordify/

12. http://www.reddit.com/r/haskell/comments/16u44u/chordify_extract_chord_sequences_from_mp3s_using/

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_snap/

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_dependent_heterogeneous/

19. http://www.timphilipwilliams.com/posts/2013-01-16-fixing-gadts.html

20. http://www.reddit.com/r/haskell/comments/16qr6q/fixing_gadts_generic_recursion_schemes_for_gadts/

21. http://www.reddit.com/r/haskell/comments/16i322/whats_the_importance_of_category_theory_in/

22. http://www.reddit.com/r/haskell/comments/16i322/whats_the_importance_of_category_theory_in/

23. http://www.youtube.com/watch?v=nCwG9ijQMuQ&t=01m22s

24. http://www.reddit.com/r/haskell/comments/16kf0j/parsing_markdown_with_parsec_how_pandoc_does_it/

25. http://www.clckwrks.com/

26. http://www.reddit.com/r/haskell/comments/168j2w/clckwrks_from_the_creator_of_happstack_is/

27. http://www.haskellforall.com/2013/01/pipes-safe-10-resource-management-and.html

28. http://www.reddit.com/r/haskell/comments/16mban/pipessafe10_resource_management_and_exception/

29. http://stackoverflow.com/questions/14401689/values-types-kinds-as-an-infinite-sequence

30. http://stackoverflow.com/questions/14309396/why-is-this-a-useful-warning-in-haskell-when-pattern-matching-defined-but-not

31. http://stackoverflow.com/questions/14295582/why-are-getargs-and-getprogname-io-actions

32. http://stackoverflow.com/questions/14273235/can-gadts-be-used-to-prove-type-inequalities-in-ghc

33. http://stackoverflow.com/questions/14349232/applying-denotational-semantics-to-design-of-programs

34. http://stackoverflow.com/questions/14357918/examples-where-compiler-optimized-functional-code-performs-better-than-imperativ

35. http://stackoverflow.com/questions/14262014/why-is-there-only-one-non-strict-function-from-int-to-int

36. http://stackoverflow.com/questions/14327327/dependency-injection-in-haskell-solving-the-task-idiomatically

37. http://stackoverflow.com/questions/14270500/what-does-a-haskell-comment-starting-with-generally-mean

38. http://stackoverflow.com/questions/14263363/is-operational-really-isomorphic-to-a-free-monad

39. https://plus.google.com/105107667630152149014/about