Re: [Haskell-cafe] sequence causing stack overflow on pretty small lists
On Tue, 27 Aug 2013, John Lato wrote: [1] Most people are physically incapable of reading documents that explain why what they want to do won't work. Even if people did read the documentation, I suspect that the people most in need of the information would be the least likely to understand how it applies to their situation. Plus: I don't expect that programmers read the documentation of 'sequence' and 'mapM' again every time they use the function. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] cpphs calls error when it finds an #error declaration
On 27 Aug 2013, at 08:33, Niklas Hambüchen wrote: @Malcolm, would you mind a change towards throwing an exception that is different from error so that it can be easily caught, or even better, a change from runCpphs :: ... - IO String to runCpphs :: ... - IO (Either String String) or similar? Have you tried simply wrapping the call to runCpphs in a catch? Something like safeRunCpphs :: ... - IO (Either String String) safeRunCpphs foo = fmap Right (runCpphs foo) `catch` (\(UserError s)- Left s If an exception based interface is kept, it would be nice to add some haddock to `runCpphs`; not knowing about the existence of #error, it is easy to assume that the IO is only used for accessing the FilePath passed in. The IO is used also for reading #include'd files, of course. I'd be happy to add some extra documentation making the behaviour on #error clearer, if you can suggest some text that would have helped you. Regards, Malcolm ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Proposal: Polymorphic typeclass and Records
Let we have data in one module as this:
data Person = Person { personId :: Int, name :: String }
data Address a = Address { personId :: Int, address :: String , way ::
a}
It was discussed a lot in topics OverloadedRecordFields
This is an alternative:
Let we have polymorphic typeclass:
class Record{f} a b | a - b where
f :: a - b
so, compiler could create instances for our data as:
instance Record{personId} Person Int where
personId (Person x _) = x
instance Record{personId} (Address a) Int where
personId (Address x _ _) = x
instance Record{way} (Address Int) Int where
way (Address _ _ x) = x
and we could use this:
p:: Record {personId} r Int = r - Int
p = personId
What do you think about this?
--
View this message in context:
http://haskell.1045720.n5.nabble.com/Proposal-Polymorphic-typeclass-and-Records-tp5735096.html
Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] cpphs calls error when it finds an #error declaration
On 29/08/13 00:43, Malcolm Wallace wrote: Have you tried simply wrapping the call to runCpphs in a catch? Something like safeRunCpphs :: ... - IO (Either String String) safeRunCpphs foo = fmap Right (runCpphs foo) `catch` (\(UserError s)- Left s Yes, that is what I'm doing at the moment. The problem with this is that it does not allow me to distinguish between a programmer error (error) on the caller or implementation side, and an #error in the input file. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Haskell Weekly News: Issue 278
Welcome to issue 278 of the HWN, an issue covering crowd-sourced bits
of information about Haskell from around the web. This issue covers the
week of August 18 to 24, 2013.
Quotes of the Week
* johnw: finger trees must be related to palm trees somehow
* monochrom: do, or undo. there is no redo. :)
* danharaj: arrows are just strong monads in the 2-category of
profunctors. what's the problem?
* BMeph: If only they knew the POWER...of the darcs-IDE!
* geekosaur: tekmo and the pipes list sounds like some kind of
postmodernist band
Top Reddit Stories
* Building an Asteroids Clone in Haskell using Netwire
Domain: ocharles.org.uk, Score: 88, Comments: 22
On Reddit: [1] http://goo.gl/HZBtcK
Original: [2] http://goo.gl/Gp8TVw
* What's new in Cabal 1.18 - sandboxes, REPL, cross-compilation and more!
Domain: coldwa.st, Score: 75, Comments: 18
On Reddit: [3] http://goo.gl/8eSChe
Original: [4] http://goo.gl/VrHkMY
* An Introduction to Cabal sandboxes
Domain: coldwa.st, Score: 64, Comments: 33
On Reddit: [5] http://goo.gl/oFGzfK
Original: [6] http://goo.gl/ByA6Ru
* Reasoning about space leaks with space invariants
Domain: apfelmus.nfshost.com, Score: 59, Comments: 48
On Reddit: [7] http://goo.gl/cKlPrM
Original: [8] http://goo.gl/E4kIjD
* Bound: Making de Bruijn Succ Less on School of Haskell by Edward Kmett
Domain: fpcomplete.com, Score: 48, Comments: 14
On Reddit: [9] http://goo.gl/v7tgWO
Original: [10] http://goo.gl/glTA3N
* PatternSynonyms - ghc trac
Domain: ghc.haskell.org, Score: 35, Comments: 14
On Reddit: [11] http://goo.gl/8zuy1T
Original: [12] http://goo.gl/5Bw6FN
* Revisiting Matrix Multiplication, Part III:
Customizing Vector by Edward Kmett
Domain: fpcomplete.com, Score: 33, Comments: 1
On Reddit: [13] http://goo.gl/hfoJJ7
Original: [14] http://goo.gl/yLUSWP
* Great new platform to increase *practical* code literacy
(with Haskell support).
Domain: mdswanson.com, Score: 29, Comments: 13
On Reddit: [15] http://goo.gl/sFLBQm
Original: [16] http://goo.gl/TIJPTi
* Bartosz' basic Haskell: Error Handling
Domain: fpcomplete.com, Score: 28, Comments: 4
On Reddit: [17] http://goo.gl/1jBaWG
Original: [18] http://goo.gl/zZrPxH
* A Pragmatic Case for Static Typing with Brian Hurt on Vimeo
(at NY-Haskell)
Domain: vimeo.com, Score: 27, Comments: 11
On Reddit: [19] http://goo.gl/uECaaB
Original: [20] http://goo.gl/59c8Wo
* Write yourself a Brainfuck in an hour
Domain: github.com, Score: 26, Comments: 13
On Reddit: [21] http://goo.gl/lAfzRf
Original: [22] http://goo.gl/cbJZ7t
Top StackOverflow Questions
* Is it possible to lazily traverse a recursive data-structure
with O(1) memory usage, tail-call optimized?
votes: 10, answers: 4
Read on SO: [23] http://goo.gl/1qsBKq
* pattern matching of the form: Option{..} -
votes: 10, answers: 1
Read on SO: [24] http://goo.gl/HY3FWY
Until next time,
[25]+Daniel Santa Cruz
References
1. http://ocharles.org.uk/blog/posts/2013-08-18-asteroids-in-netwire.html
2.
http://www.reddit.com/r/haskell/comments/1kmes7/building_an_asteroids_clone_in_haskell_using/
3. http://coldwa.st/e/blog/2013-08-21-Cabal-1-18.html
4.
http://www.reddit.com/r/haskell/comments/1kslyi/whats_new_in_cabal_118_sandboxes_repl/
5. http://coldwa.st/e/blog/2013-08-20-Cabal-sandbox.html
6.
http://www.reddit.com/r/haskell/comments/1kpynl/an_introduction_to_cabal_sandboxes/
7. http://apfelmus.nfshost.com/blog/2013/08/21-space-invariants.html
8.
http://www.reddit.com/r/haskell/comments/1ksu0v/reasoning_about_space_leaks_with_space_invariants/
9. https://www.fpcomplete.com/user/edwardk/bound
10.
http://www.reddit.com/r/haskell/comments/1knvz2/bound_making_de_bruijn_succ_less_on_school_of/
11. http://ghc.haskell.org/trac/ghc/wiki/PatternSynonyms
12.
http://www.reddit.com/r/haskell/comments/1kmods/patternsynonyms_ghc_trac/
13.
https://www.fpcomplete.com/user/edwardk/revisiting-matrix-multiplication-part-3
14.
http://www.reddit.com/r/haskell/comments/1kmvs2/revisiting_matrix_multiplication_part_iii/
15. http://mdswanson.com/blog/2013/08/19/how-to-practice-code-reviews.html
16.
http://www.reddit.com/r/haskell/comments/1krc6t/great_new_platform_to_increase_practical_code/
17.
https://www.fpcomplete.com/user/bartosz/basics-of-haskell/10_Error_Handling
18.
http://www.reddit.com/r/haskell/comments/1ksjt4/bartosz_basic_haskell_error_handling/
19. https://vimeo.com/72870631
20.
http://www.reddit.com/r/haskell/comments/1kusbt/a_pragmatic_case_for_static_typing_with_brian/
21.
https://github.com/quchen/articles/blob/master/write_yourself_a_brainfuck.md
22.
http://www.reddit.com/r/haskell/comments/1kz39d/write_yourself_a_brainfuck_in_an_hour/
23.
[Haskell-cafe] Building recent Cabal/cabal-install
Greetings café, There are some problems in Haddock to do with Template Haskell that I believe are being caused by Cabal. These were apparently addressed in 1.18 which came out recently. ‘Great!’, I thought. My problem is that I'm unsure how to use 1.18. I'm using GHC HEAD (well, 3 days old now) which is meant to come with Cabal 1.18 (the library) and in fact it seems to ship with it. Running ‘cabal --version’ however: cabal-install version 1.17.0 using version 1.17.0 of the Cabal library I'm unsure how to get it to use 1.18. I tried to build cabal-install from git but that just complains about dependencies not being possible to resolve: it depends on HTTP which depends on base 4.7 but 4.7 comes with GHC HEAD! I am baffled as to how I should go about using 1.18 and would love to hear from some people who have this up and running. -- Mateusz K. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
