May 2015 - Haskell-Cafe

Re: [Haskell-cafe] Any recommendations on how to interact with the running state of a program?
by Anatoly Yakovenko 29 May '15

29 May '15

How would the program get updated values? via an IORef? This thing is running until the user decides the output looks good Anatoly On Thu, May 28, 2015 at 12:16 PM Carlos López-Camey <c.lopez(a)kmels.net> wrote: > Cloud Haskell + Event streaming via some Protocol (like json on > websockets) ? > > > > 2015-05-25 15:14 GMT-06:00 Anatoly Yakovenko <aeyakovenko(a)gmail.com>: > >> I am playing around with some deep learning algorithms and I need a way >> to periodically read the intermediate result and change some of the system >> variables. >> >> Any ideas on how to best approach this problem? I was thinking of >> something basic, like having the program periodically read and write from >> some files. >> >> Thanks, >> Anatoly >> >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe >> >> >

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Haskell wiki: user account
by Julien Cretel 29 May '15

29 May '15

Hi there, I'd like to get a user account for the Haskell wiki. Desired username: Jubobs Cheers -- Julien Cretel PhD student University College Cork, Ireland Email: j.cretel(a)umail.ucc.ie

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Anyone using Tidal/emacs like emacs-live/overtone?
by Cody Goodman 29 May '15

29 May '15

Does anyone have a working setup where you enter Haskell code from the tidal library and use a keybinding to execute that statement (or multiple)? Basically wanting to try livecoding Tidal code like all the overtone videos: https://vimeo.com/22798433

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help with glfw seg-fault
by briand＠aracnet.com 29 May '15

29 May '15

Hi, GLFW.swapBuffers w is the culprit. Not sure where to go from there. That's a pretty low level failure. Any suggestions. Brian

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Type inference doesn't always calculate the most generic type?
by Christophe Delord 28 May '15

28 May '15

Hello, I'm new here. Sorry if this question has already been asked. I have noticed something strange about type inference. Prelude> :t abs abs :: Num a => a -> a Prelude> let mapabs = map abs Prelude> :t mapabs mapabs :: [Integer] -> [Integer] Prelude> :t (map abs) (map abs) :: Num b => [b] -> [b] I think that "mapabs" and "map abs" should have the same generic type. In a program I can force the type like this: mapabs = map abs mapabs' :: (Num a) => [a] -> [a] mapabs' = map abs but mapabs still have the type [Integer] -> [Integer] Are there any reason for this? Regards, Christophe Delord.

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(Why) must this function remain nameless?
by Clinton Mead 28 May '15

28 May '15

The following code (somewhat contrived) code compiles on GHC without issue, and towards the end repeatedly uses the lambda function "(\fn (D x) -> f fn x)". But when I simply try to give it a name, like so: h = (\fn (D x) -> f fn x) I then get a compile error. How can I name this function, or must it remain forever nameless? ( Ideone link: http://ideone.com/mtuYnK ) --- {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE UndecidableInstances #-} {-# LANGUAGE OverlappingInstances #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE ExistentialQuantification #-} {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE NoMonomorphismRestriction #-} import GHC.Exts (Constraint) type family Parent a class C a b where f :: b -> a -> String instance (C (Parent a) b) => C a b where f _ _ = f (undefined :: b) (undefined :: Parent a) data A1 = A1 data A2 = A2 data A3 = A3 data A4 = A4 type instance Parent A2 = A1 type instance Parent A3 = A2 type instance Parent A4 = A3 data F1 = F1 data F3 = F3 instance C A1 F1 where f _ _ = "F1" instance C A3 F3 where f _ _ = "F3" type family Constraints t a :: Constraint data D t = forall a. (Constraints t a) => D a type instance Constraints A1 a = (C a F1) type instance Constraints A2 a = (C a F1, C a F3) type instance Constraints A3 a = (C a F1, C a F3) type instance Constraints A4 a = (C a F1, C a F3) main = do putStrLn (f F1 A1) putStrLn (f F1 A2) putStrLn (f F1 A3) putStrLn (f F1 A4) putStrLn (f F3 A3) putStrLn (f F3 A4) putStrLn $ (\fn (D x) -> f fn x) F1 ((D A1) :: D A1) putStrLn $ (\fn (D x) -> f fn x) F1 ((D A2) :: D A1) putStrLn $ (\fn (D x) -> f fn x) F3 ((D A3) :: D A2) -- h = (\fn (D x) -> f fn x)

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Re: [Haskell-cafe] pqueue - repository and maintainer (taking over)
by Louis Wasserman 28 May '15

28 May '15

No, it's not; I never did put it up on github. On Wed, May 27, 2015 at 11:18 PM Tobias Brandt <tob.brandt(a)gmail.com> wrote: > I have an open pull request for this issue since February: > https://github.com/bumptech/haskell-pqueue/pull/2 > > But I don't even know whether this is the official repository. > > On Wed, May 27, 2015 at 10:01 PM lennart spitzner < > lsp(a)informatik.uni-kiel.de> wrote: > >> Greetings, >> >> Regarding the pqueue package: >> >> 1) Does anyone have any (additional) contact details for the current >> maintainer/author, Louis Wasserman? >> 2) Is the package's repository available anywhere? The darcs link >> listed in the package 404s. >> 3) I would be willing to take over for basic maintenance if the >> current maintainer is unavailable. >> >> The pqueue package does not compile with ghc-7.10. Fixing requires >> just some quick changes (i have a working version locally). The last >> upload for the package is from 2012, but the author's github account >> lowasser shows some more recent activity. Yet I have not received a >> reply to my e-mail from six weeks ago. >> >> Lennart >> > _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe >> >

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Libraries Mailing Problem?
by Dominic Steinitz 28 May '15

28 May '15

Is there something wrong with the libraries mailing list? There doesn’t seem to have been any traffic since 18 May: https://mail.haskell.org/pipermail/libraries/2015-May/date.html <https://mail.haskell.org/pipermail/libraries/2015-May/date.html> Dominic Steinitz dominic(a)steinitz.org http://idontgetoutmuch.wordpress.com

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International Conference on Live Coding, 13-15 July, Registration open
by alex 28 May '15

28 May '15

First International Conference on Live Coding ICSRiM, School of Music, University of Leeds 13th-15th July 2015 http://iclc.livecodenetwork.org/ We are happy to announce that registration for ICLC2015 is now open. Live coding turns programming languages into live interfaces, allowing us to directly manipulate computation via its notation. Live coding has great potential, being used for example to create improvised music and visuals, to allow developers to collaborate in new ways, to better understand computational models by making fundamental changes to them on-the-fly, and to find new ways to learn and teach programming. Since the beginning of the TOPLAP movement in 2003 (building on an extensive but hidden pre-history), live coding has grown fast, attracting interest from many people in artistic, creative, scientific, educational, business and mixed contexts. After a good number of international events, the time is right to bring these people together for an academic conference, exchanging ideas and techniques, and enjoying dozens of peer reviewed papers and performances. The conference will also open up the field for people new to live coding, so they may develop and contribute their own perspectives on this emerging field. Join us! Registration is £80 (£50 concessions) for the three day conference including lunches, evening events, and more. See the website for details of the developing programme: http://iclc.livecodenetwork.org/ And register here, completing both the on-line payment and registration forms: http://iclc.livecodenetwork.org/registration.html ICLC is organised by the Live Coding Research Network, which is funded by the Arts and Humanities Research Council. -- http://yaxu.org/

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no Web-Security component in Haskell?
by Thomas Koch 28 May '15

28 May '15

Hallo, I did not found anything comparable to Spring Security[1][2] (Java) or Symfony Security[3] (PHP) in Haskell. Both components are used in web applications to grant or deny access to resources based on roles, ACLs or custom voters. A naive strategy would be to port the concepts of both components, which are very similar, to Haskell. They represent a lot of accumulated knowledge from many experts about web security. Or are there better ways to do web security in a powerful language like Haskell? Regards, Thomas Koch [1] http://projects.spring.io/spring-security [2] http://docs.spring.io/autorepo/docs/spring-security/3.1.7.RELEASE/apidocs [3] http://api.symfony.com/master/Symfony/Component/Security/Core/SecurityConte…

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