- Haskell-Cafe - Haskell.org

Call for Participation: Workshop on Functional Art, Music, Modeling and Design
by Brent Yorgey 08 Aug '13

08 Aug '13

====================================================================== FARM 2013: Call for Participation ACM SIGPLAN Workshop on Functional Art, Music, Modeling and Design Boston, Massachusetts, USA 28th September, 2013 (directly after ICFP) http://www.cis.upenn.edu/~byorgey/farm13/ ====================================================================== The functional programming community is largely interested in writing beautiful programs. This workshop is intended to gather researchers and practitioners interested in writing beautiful programs that generate beautiful artifacts. Such artifacts may include visual art, music, 3D sculptures, animations, GUIs, video games, physical models, architectural models, choreographies for dance, poetry, and even physical objects such as VLSI layouts, GPU configurations, or mechanical engineering designs. The goal of FARM is to gather together researchers, practitioners, and educators in this interdisciplinary field, as well as anyone else with even a casual interest in the area. We wish to share ideas, look for common ground, and encourage more activity. We also hope to legitimize work in the field and facilitate potential collaboration among the participants. Registration ------------ Deadline for early registration: 22 August 2013 https://regmaster3.com/2013conf/ICFP13/register.php This is the registration site for ICFP 2013 and all the affiliated workshops including FARM 2013. Accepted papers and demonstrations ---------------------------------- - Samuel Aaron and Alan F. Blackwell. From Sonic Pi to Overtone: Creative Musical Experiences with Domain-Speciﬁc and Functional Languages - Henrik Bäärnhielm, Mikael Vejdemo-Johansson and Daniel Sundström. Using Haskell as DSL for controlling immersive media experiences (Demo) - Guillaume Baudart, Louis Mandel and Marc Pouzet. Programming Mixed Music in ReactiveML - Jean Bresson, Raphael Foulon and Marco Stroppa. Reduction as a Transition Controller for Sound Synthesis Events - Kelsey D'Souza. PySTEMM - A STEM Learning Tool for Exploring and Building Executable Concept Models (Demo) - Andy Gill and Brent A. Yorgey. Functional active animation (Demo) - Jason Hemann and Eric Holk. Visualizing the Turing Tarpit - Paul Hudak. Euterpea: From Signals to Symphonies (Demo) - David Janin, Florent Berthaut, Myriam Desainte-Catherine, Yann Orlarey and Sylvain Salvati. The T-Calculus : towards a structured programing of (musical) time and space - David Janin and Florent Berthaut. LiveTuiles for tiled composition of audio patterns (Demo) - Thomas Jordan. Spontaneous Musical Explorations of Visible Symmetric Structures (Demo) - Hendrik Vincent Koops, José Pedro Magalhães and W. Bas de Haas. A Functional Approach To Automatic Melody Harmonisation - José Pedro Magalhães, Bas De Haas, Gijs Bekenkamp, Dion ten Heggeler and Tijmen Ruizendaal. Chordify: Chord Transcription for the Masses (Demo) - Donya Quick and Paul Hudak. Grammar-Based Automated Music Composition in Haskell - Chung‐chieh Shan and Dylan Thurston. Braiding in circles (Demo) Workshop Organization --------------------- Workshop Chair: Paul Hudak Program Chair: Conal Elliott Publicity Chair: Brent Yorgey Program Committee ----------------- - Daniel Cukier (AgileAndArt) - Conal Elliott (Tabula) (chair) - Kathleen Fisher (Tufts University) - Richard Gabriel (IBM Research) - George Giorgidze (University of Tübingen) - Paul Hudak (Yale University) - José Pedro Magalhães (University of Oxford) - Alex McLean (University of Leeds) - John Peterson (Western State Colorado University) - Michael Sperber (Active Group) - Henning Thielemann (Martin-Luther-Universität Halle-Wittenberg) - Brent Yorgey (University of Pennsylvania)

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Proposal for adding finallyError to MonadError
by David Sorokin 08 Aug '13

08 Aug '13

Hi, Café! I have a proposal. I offer to add a new function to the MonadError type class: finallyError :: MonadError e m => m a -> m b -> m a This is a generalization of the standard finally function that has the following signature: finally: IO a -> IO b -> IO a Like function finally, the finallyError function runs the first computation and then runs the second computation regardless of whether an error might arise in the first computation. The first computation defines the result. Introducing semantics of a possible cancellation of the m computation, the finallyError function accepts an additional meaning. The second computation must be performed even in case of cancelling the computation, while function catchError must be ignored. It literally means that the finallyError function cannot be expressed in terms of the catchError function. This idea is essentially inspired by the F# async workflow that does allow cancelling the Async computation. I implemented a similar monad Simulation.Aivika.Cont.Cont for my simulation library Aivika [1]. My monad Cont is an extension of the standard monad with the same name. It uses continuations (namely, three different continuations within one computation). It supports the exception handling and it allows cancelling the computation (the liftIO function should also call finallyError to catch the possible cancellation event if my Cont was a generic monad transformer). In the simulation the cancellation of the computation (actually, of the discontinuous process) is a typical use case. Therefore it should be executed as fast as possible. If I raised a specialized IOException for the cancellation event, then it would be a more costly operation. This is a practical point why the finallyError function cannot be expressed in terms of catchError. Another reason is that the catchError function can eat the cancellation exception, which would be absolutely unacceptable. This is a theoretical reason for introducing finallyError. The finallyError function is very useful for guaranteed releasing the external resources (such as the modeled entities in Aivika) in case of raising an exception and even in case of cancelling the active computation, which is important for simulation, for example. Regarding the standard instances of MonadError, the finallyError function seems to be simple for implementing. It is difficult mainly for the Cont-based monads. So, in Aivika it is more difficult than catchError for my Cont monad. The actual name of the function is not important but here it looks consistent with other functions of the MonadError type class. Finally, the finallyError function can be actually defined in an additional type class, which would extend MonadError like that how the ArrowChoice type class extends Arrow. Kind regards, David Sorokin [1] https://github.com/dsorokin/aivika

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Why are field selectors functions? [was: ghc-users A possible alternative to dot notation for record access]
by AntC 08 Aug '13

08 Aug '13

No! This isn't more bikeshedding about notation. It's a bit of Haskell archaeology. > On Sun, Jun 30, 2013 at 2:59 AM, Judah Jacobson wrote: [This isn't exactly what Judah wrote.] > ... > > Instead of `x f` (to access field x of record f), > maybe we could write `f{x}` as the record selection. > The more I thought about that ... We use { ... } to declare records, build them, update them. We use { ... } in pattern matching to access named fields. Why don't we use { ... } to access named fields in terms? The syntax `e{ foo }` is unused in H98. (Or at least it was in 1998.) Can someone who was there at the time (1994?, TRex?) remember if that was ever considered? In the declaration, the build/update, and pattern match: data R = MkR { foo :: Int } r = MkR { foo = 7 } \ (MkFoo { foo }) -> ... -- using NamedFieldPuns `foo` is clearly bound to an Int. So why is there this `foo` thing that isn't an Int? AntC

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ANN: Monad.Reader Issue 22
by Edward Z. Yang 08 Aug '13

08 Aug '13

I am pleased to announce that Issue 22 of the Monad Reader is now available. http://themonadreader.files.wordpress.com/2013/08/issue22.pdf Issue 22 consists of the following two articles: * "Generalized Algebraic Data Types in Haskell" by Anton Dergunov * "Error Reporting Parsers: a Monad Transformer Approach" by Matt Fenwick and Jay Vyas * "Two Monoids for Approximating NP-Complete Problems" by Mike Izbicki Feel free to browse the source files. You can check out the entire repository using Git: git clone https://github.com/ezyang/tmr-issue22.git If you’d like to write something for Issue 23, please get in touch! Cheers, Edward

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Is there a Galois correspondence between a Haskell class hierarchy and a given instance hierarchy?
by Patrick Browne 08 Aug '13

08 Aug '13

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ANNOUNCE: tasty, a new testing framework
by Roman Cheplyaka 08 Aug '13

08 Aug '13

I am pleased to announce the first release of tasty, a new testing framework for Haskell. It is meant to be a successor to test-framework (which is unmaintained). Tasty supports HUnit, SmallCheck, QuickCheck, and golden tests out of the box (through the standard packages), but it is very extensible, so you can write your own test providers. Please see the home page for more information: http://documentup.com/feuerbach/tasty Roman

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Module names from a function name
by Jong-won Choi 08 Aug '13

08 Aug '13

Hi, I asked this question to beginner mailing list and no luck so far, so I'm trying here. How can I get all the module names which (re-)export a given function name? I'd like to fix Emacs Haskell mode - interactive documentation browser and I need the list of such module names. Thanks! - Jong-won

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Re: [Haskell-cafe] Module names from a function name
by Jong-won Choi 08 Aug '13

08 Aug '13

Thanks for the suggestion, but I am looking for a programmatic way. Is module in Haskell first class object? Does it maintain function names which are exported? On 08/08/13 12:41, Patrick Mylund Nielsen wrote: > > hoogle <function name> after running cabal install hoogle and hoogle data > > On Aug 7, 2013 10:35 PM, "Jong-won Choi" <oz.jongwon.choi(a)gmail.com > <mailto:oz.jongwon.choi@gmail.com>> wrote: > > Hi, > > I asked this question to beginner mailing list and no luck so far, > so I'm trying here. > > How can I get all the module names which (re-)export a given > function name? > > I'd like to fix Emacs Haskell mode - interactive documentation > browser and I need the list of such module names. > > Thanks! > > - Jong-won > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org <mailto:Haskell-Cafe@haskell.org> > http://www.haskell.org/mailman/listinfo/haskell-cafe >

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Haskell Weekly News: Issue 275
by Daniel Santa Cruz 08 Aug '13

08 Aug '13

Welcome to issue 275 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers the week of July 28 to August 3, 2013. Quotes of the Week * littlecalculist: combinatorics. n. math's way of punishing you for failing to use abstraction. * dmwit: ?let instance Num Bool where (+) = (/=); (*) = (&&); negate = id; abs = id; signum = id; fromInteger = odd * edwardk: clearly it should be \x -> x <$ do f . g $ x. do is a magical () killing machine * dmwit: Type families are not injective. Your first three inscrutable error messages with type families in them will be because you don't understand this rule. * elliott: halting problem, n. the property which makes stating anything about programs impossible, according to at least one person in any room * carmack: Everything that is syntactically legal that the compiler will accept will eventually wind up in your codebase. Top Reddit Stories * John Carmack talking at length about Haskell in his QuakeCon Keynote speech (live) Domain: twitch.tv, Score: 105, Comments: 47 On Reddit: [1] http://goo.gl/1g1zqD Original: [2] http://goo.gl/C17ci8 * SPJ: GHC's Glorious future Domain: haskell.org, Score: 79, Comments: 16 On Reddit: [3] http://goo.gl/97DGuc Original: [4] http://goo.gl/YAY6wC * There's a massive gap between the "average" and "expert" Haskeller. How do I bridge that gap? Domain: self.haskell, Score: 73, Comments: 53 On Reddit: [5] http://goo.gl/Y3jEoa Original: [6] http://goo.gl/Y3jEoa * Getting Started With GHC Hacking Domain: dagit.github.io, Score: 64, Comments: 2 On Reddit: [7] http://goo.gl/ZwHVpm Original: [8] http://goo.gl/ljhyff * Extensible Effects: An Alternative to Monad Transformers Domain: cs.indiana.edu, Score: 63, Comments: 47 On Reddit: [9] http://goo.gl/2JqImi Original: [10] http://goo.gl/zq5klw * The Intel Labs Haskell Research Compiler [pdf] Domain: leafpetersen.com, Score: 55, Comments: 19 On Reddit: [11] http://goo.gl/wRQs7E Original: [12] http://goo.gl/2eZhEX * Goto in Haskell Domain: self.haskell, Score: 36, Comments: 34 On Reddit: [13] http://goo.gl/pelEJo Original: [14] http://goo.gl/pelEJo * The Algebra of Algebraic Data Type Domain: chris-taylor.github.io, Score: 35, Comments: 3 On Reddit: [15] http://goo.gl/PPi0M1 Original: [16] http://goo.gl/xE78Ko * Functors and monads for analyzing data Domain: izbicki.me, Score: 32, Comments: 16 On Reddit: [17] http://goo.gl/42ux1T Original: [18] http://goo.gl/LAJ7ti * Why use _ <-? Domain: self.haskell, Score: 31, Comments: 24 On Reddit: [19] http://goo.gl/QpGPP1 Original: [20] http://goo.gl/QpGPP1 * CIS 194: Introduction to Haskell (Spring 2013) Domain: cis.upenn.edu, Score: 30, Comments: 3 On Reddit: [21] http://goo.gl/9zHuXb Original: [22] http://goo.gl/cNyEOT * The Commutative monad Domain: gelisam.blogspot.ca, Score: 30, Comments: 41 On Reddit: [23] http://goo.gl/kDVTrl Original: [24] http://goo.gl/mTCHL0 * FRP GUI - reactive-banana + threepenny-gui = awesome Domain: apfelmus.nfshost.com, Score: 30, Comments: 11 On Reddit: [25] http://goo.gl/xu91UA Original: [26] http://goo.gl/9Vu6ng Top StackOverflow Questions * Monad Stack Penetration Classes with Free/Operational Monad Transformers? votes: 16, answers: 1 Read on SO: [27] http://goo.gl/t4F6kd * Haskell reexport everything votes: 12, answers: 1 Read on SO: [28] http://goo.gl/7HQCVC * What are the main differences between Scala and Frege (in programming paradigms)? votes: 11, answers: 2 Read on SO: [29] http://goo.gl/TRhjDB * If a thunk results in an exception, is the exception kept as the result of the thunk? votes: 10, answers: 1 Read on SO: [30] http://goo.gl/rPSd6J * Check if import is redundant votes: 9, answers: 1 Read on SO: [31] http://goo.gl/jEqBnt * Haskell Parser Combinators votes: 9, answers: 1 Read on SO: [32] http://goo.gl/YCrsX3 * A library implementation of a recursion scheme votes: 8, answers: 1 Read on SO: [33] http://goo.gl/DdYPtw Until next time, [34]+Daniel Santa Cruz References 1. http://www.twitch.tv/bethesda?utm_campaign=live_embed_click&utm_source=www.… 2. http://www.reddit.com/r/haskell/comments/1jj40p/john_carmack_talking_at_len… 3. http://www.haskell.org/pipermail/ghc-devs/2013-August/001818.html 4. http://www.reddit.com/r/haskell/comments/1jky60/spj_ghcs_glorious_future/ 5. http://www.reddit.com/r/haskell/comments/1jeo0p/theres_a_massive_gap_betwee… 6. http://www.reddit.com/r/haskell/comments/1jeo0p/theres_a_massive_gap_betwee… 7. http://dagit.github.io/posts/2013-08-03-getting-started-with-ghc-hacking.ht… 8. http://www.reddit.com/r/haskell/comments/1jnaz5/getting_started_with_ghc_ha… 9. http://www.cs.indiana.edu/~sabry/papers/exteff.pdf 10. http://www.reddit.com/r/haskell/comments/1j9n5y/extensible_effects_an_alter… 11. http://www.leafpetersen.com/leaf/publications/hs2013/hrc-paper.pdf 12. http://www.reddit.com/r/haskell/comments/1jh4iv/the_intel_labs_haskell_rese… 13. http://www.reddit.com/r/haskell/comments/1jk06q/goto_in_haskell/ 14. http://www.reddit.com/r/haskell/comments/1jk06q/goto_in_haskell/ 15. http://chris-taylor.github.io/blog/2013/02/13/the-algebra-of-algebraic-data… 16. http://www.reddit.com/r/haskell/comments/1jhq7k/the_algebra_of_algebraic_da… 17. http://izbicki.me/blog/functors-and-monads-for-analyzing-data 18. http://www.reddit.com/r/haskell/comments/1ja3js/functors_and_monads_for_ana… 19. http://www.reddit.com/r/haskell/comments/1jcls5/why_use/ 20. http://www.reddit.com/r/haskell/comments/1jcls5/why_use/ 21. http://www.cis.upenn.edu/~cis194/ 22. http://www.reddit.com/r/haskell/comments/1j9m5e/cis_194_introduction_to_has… 23. http://gelisam.blogspot.ca/2013/07/the-commutative-monad.html 24. http://www.reddit.com/r/haskell/comments/1jegxb/the_commutative_monad/ 25. http://apfelmus.nfshost.com/blog/2013/08/02-reactive-banana-threepenny.html 26. http://www.reddit.com/r/haskell/comments/1jk16t/frp_gui_reactivebanana_thre… 27. http://stackoverflow.com/questions/17936900/monad-stack-penetration-classes… 28. http://stackoverflow.com/questions/18035458/haskell-reexport-everything 29. http://stackoverflow.com/questions/17905322/what-are-the-main-differences-b… 30. http://stackoverflow.com/questions/18018254/if-a-thunk-results-in-an-except… 31. http://stackoverflow.com/questions/17904265/check-if-import-is-redundant 32. http://stackoverflow.com/questions/18028220/haskell-parser-combinators 33. http://stackoverflow.com/questions/18013547/a-library-implementation-of-a-r… 34. https://plus.google.com/105107667630152149014/about

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Hackage upload problem
by Thomas Hallgren 07 Aug '13

07 Aug '13

Hi, I get the following error when I try to upload gf-3.5.tar.gz [1] to Hackage. 400 Error in upload could not extract gf-3.5 directory from gf-3.5.tar.gz I get the same error when I try to Check the previous version, gf-3.4.tar.gz [2], which was uploaded without problems 6 months ago [3], so it seems that something has changed on the server. Does anyone know what it could be that is going wrong? Is there a way to get a more informative error message? Thomas H [1] http://www.grammaticalframework.org/download/gf-3.5.tar.gz [2] http://www.grammaticalframework.org/download/gf-3.4.tar.gz [3] http://hackage.haskell.org/package/gf-3.4

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