April 2012 - Haskell-Cafe

[Announce] wxHaskell 0.90
by Jeremy O'Donoghue 14 Apr '12

14 Apr '12

Hi Haskellers, I am delighted to announce the release of wxHaskell 0.90. This release represents a significant milestone for us as it includes support for wxWidgets 2.9.x. The release is avalable from Hackage and as a darcs repo from http://code.haskell.org/wxhaskell. Build and installation instructions have been updated on the Haskell wiki at http://www.haskell.org/haskellwiki/Wxhaskell. Highlights of the new release: - Builds and runs cleanly on 64 bit platforms (particularly MacOS X Lion). - The wxWidgets C wrapper is now built as a DLL on all platforms. - This is reported to enable meaningful use of wxHaskell in GHCi, at least on OS X and Windows. - It also theoretically allows wxc to be used independently of wxHaskell as the basis of a wxWidgets wrapper for other programming languages. Some D language hackers have expressed an interest in this. - New controls: - Styled Text Control (actually, this is reinstated as it was 'lost' a while back during cabalization) - OpenGL support - PropertyGrid control - Many events added in anticipation of wrapping more controls in the near future. There were many contributors to this release, the most notable being Dave Tapley (with the generous support of Mentics Inc.). Dave was responsible for the refactoring of wxc and PropertyGrid support. Eric Kow put in quite a bit of work with Kenny Frodo, Doaitse Swierstra and Alessandro Vermeulen on MacOS support. There were a couple of contributions from long-time wxHaskell contributor shelarcy, and bug reports, fixes and support from a larger community than I ever realised we had. Support for wxWidgets 2.8.x will continue in a 'maintenance mode' continuing from the wxHaskell 0.13 codeline. If you continue to use the old codeline, please take note of the changes to the procedure to get the correct version for your needs. This is also documented at http://www.haskell.org/haskellwiki/Wxhaskell. Thanks to everyone involved. Best regards Jeremy

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Final CFP: 16th Brazilian Symposium on Programming Languages
by Simon Thompson 14 Apr '12

14 Apr '12

============================================================ CALL FOR PAPERS 16th BRAZILIAN SYMPOSIUM ON PROGRAMMING LANGUAGES Natal, Rio Grande do Norte, Brazil September 24-28, 2012 http://www.cbsoft.dimap.ufrn.br ============================================================ IMPORTANT DATES Paper abstract submission (15 lines): April 27th, 2012 (extended) Full paper submission: May 4th, 2012 (extended) Notification of acceptance: June 4th, 2012 Final papers due: June 29th, 2012 INTRODUCTION The 16th Brazilian Symposium on Programming Languages, SBLP 2012, will be held in Natal, Brazil, on September 24-28, 2012. SBLP provides a venue for researchers and practitioners interested in the fundamental principles and innovations in the design and implementation of programming languages and systems. The symposium will be part of the 3rd Brazilian Conference on Software: Theory and Practice, CBSoft 2012, http://www.cbsoft.dimap.ufrn.br, which will host four traditional, well-established symposia: * XXVI Brazilian Symposium on Software Engineering (SBES) * XVI Brazilian Symposium on Programming Languages (SBLP) * XV Brazilian Symposium on Formal Methods (SBMF) * VI Brazilian Symposium on Components, Software Architecture and Software Reuse (SBCARS) SBLP 2012 invites authors to contribute with technical papers related (but not limited) to: * Program generation and transformation, including domain-specific languages and model-driven development in the context of programming languages. * Programming paradigms and styles, including functional, object-oriented, aspect-oriented, scripting languages, real-time, service-oriented, multithreaded, parallel, and distributed programming. * Formal semantics and theoretical foundations, including denotational, operational, algebraic and categorical. * Program analysis and verification, including type systems, static analysis and abstract interpretation. * Programming language design and implementation, including new programming models, programming language environments, compilation and interpretation techniques. SUBMISSIONS Contributions should be written in Portuguese or English. We solicit papers that should fall into one of two different categories: full papers, with at most 15 pages, or short papers, with at most 5 pages. We encourage the submission of short papers reporting on partial results of on-going master dissertations or doctoral theses. All accepted papers will be published in the conference proceedings distributed in a digital media by the CBSOFT organizers. Full papers submitted in English will be published in a volume of the Lecture Notes in Computer Science (LNCS), by Springer, to be distributed in the conference. For this reason, all papers must be prepared using the LNCS template, available at http://www.springer.com/computer/lncs?SGWID=0-164-6-793341-0. As in previous editions, a journal special issue, with selected papers from accepted contributions, is anticipated. Selected papers from 2003 to 2008 editions of SBLP were published in special issues of the Journal of Universal Computer Science, by Springer. The post-proceedings of SBLP from 2009 to 2011, also with selected papers from the conference proceedings, are being edited as special issues of Science of Computer Programming, published by Elsevier. Submissions should be done using SBLP 2012 installation of the EasyChair conference management system at http://www.easychair.org/conferences/?conf=sblp2012. GENERAL CO-CHAIRS NÈlio Cacho, UFRN Gibeon Aquino, UFRN Martin Musicante, UFRN PROGRAMME CHAIRS Francisco Heron de Carvalho Junior, UFC Luis Soares Barbosa, Univ. do Minho PROGRAMME COMMITTEE * Alberto Pardo, Univ. de La Republica * Alex Garcia, IME * Alvaro Freitas Moreira, UFRGS * AndrÈ Rauber Du Bois, UFPel * Andre Santos, UFPE * Carlos Camarao, UFMG * Christiano Braga, UFF * Fernando Castor Filho, UFPE * Fernando Quint„o Pereira, UFMG * Francisco Heron de Carvalho Junior, UFC (co-chair) * Joao Saraiva, Universidade do Minho * Jo„o F. Ferreira, Teesside University * Jonathan Aldrich, Carnegie Mellon Univ. * Jose Luiz Fiadeiro, Univ. of Leicester * Lucilia Figueiredo, UFOP * Luis Soares Barbosa, Univ. do Minho (co-chair) * Manuel AntÛnio Martins, Univ. de Aveiro * Marcelo A. Maia, UFU * Marcello Bonsangue, Leiden Univ/CWI * Marcelo d'Amorim, UFPE * Marco Tulio Valente, UFMG * Mariza A. S. Bigonha, UFMG * Martin A. Musicante, UFRN * Noemi Rodriguez, PUC-Rio * Paulo Borba, UFPE * Peter Mosses, Swansea University * Qiu Zongyang, Peking University * Rafael Dueire Lins, UFPE * Renato Cerqueira, PUC-Rio * Ricardo Massa, UFPE * Roberto S. Bigonha, UFMG * Roberto Ierusalimschy, PUC-Rio * Sandro Rigo, UNICAMP * Sergio Soares, UFPE * Simon Thompson, Univ. of Kent * Varmo Vene, Univ. de Tartu Simon Thompson | Professor of Logic and Computation School of Computing | University of Kent | Canterbury, CT2 7NF, UK s.j.thompson(a)kent.ac.uk | M +44 7986 085754 | W www.cs.kent.ac.uk/~sjt

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Re: [Haskell-cafe] [Haskell] ANNOUNCE: notcpp-0.0.1
by Facundo Domínguez 14 Apr '12

14 Apr '12

Hi, > scopeLookup :: String -> Q Exp The example provided here [1] fails at runtime is no name can be found in scope. Would it make more sense to have scopeLookup :: [String] -> Q Exp and have compilation fail if no name in the list is in scope? By the way, the library brings an interesting approach to conditional compilation. Facundo [1] http://hackage.haskell.org/packages/archive/notcpp/0.0.1/doc/html/NotCPP-Sc…

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Re: [Haskell-cafe] [Haskell] ANNOUNCE: notcpp-0.0.1
by Henning Thielemann 14 Apr '12

14 Apr '12

On Fri, 13 Apr 2012, Ben Millwood wrote: > But I never liked using CPP: it completely defeats haskell-src-exts > and hence things like SourceGraph, and anyway it's not designed for > Haskell and doesn't at all understand its structure, or fit with its > syntax. With a little thought, I wondered if creative use of template > haskell might not achieve the same goal. It turned out it did, and > emboldened with this knowledge I set out to write a new package making > this technique available to others. I never liked CPP in Haskell, too. The problem is: I also do not like Template Haskell. :-) Whereever possible I use a Cabal flag and a conditional Hs-Source-Dirs. http://www.haskell.org/haskellwiki/Cabal/Developer-FAQ#Adapt_to_different_s…

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is this an arrow?
by Johannes Waldmann 13 Apr '12

13 Apr '12

Dear Cafe, I have the following types: type Computer a b = ( a -> IO ( Maybe b ) ) type Transformer a b c d = Computer a ( b, c -> d ) For example, a SAT solver: minisat :: Computer CNF Assignment, and when I use it to solve an application problem via transformation to SAT, I need t :: Transformer Problem SAT Assignment Solution Now - what is the proper abstraction? Is this an arrow somehow? And is there already a type and a library that would contain useful combinators like some of these: http://autolat.imn.htwk-leipzig.de/gitweb/?p=box;a=blob;f=src/exotic/Strate… Thanks - J.W.

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Can cabal detect property of the platform ?
by Vincent Hanquez 13 Apr '12

13 Apr '12

Hi Cafe, Is there a way to have (some) cabal flags to autoconfigure themselves ? For example, a SSE flag, i want the configure to default to on when the building machine has SSE instruction available, and default to off otherwise. (of course, it wouldn't affect the user ability to override the default with -f) It doesn't appears possible just using the cabal file. Is there a way with the Setup.hs maybe ? or some other cunning plan ? -- Vincent

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open source project for student
by Dan Cristian Octavian 13 Apr '12

13 Apr '12

Hello, I am a second year computer science student who is very interested in working on a haskell open source project. I have no particular focus on a certain type of application. I am open to ideas and to exploring new fields. What kind of project should I look for considering that I am a beginner? (Any particular project proposals would be greatly appreciated). Is the entry bar too high for most projects out there for somebody lacking experience such as me so that I should try getting some experience on my own first? Would it be a better idea to try to hack on my own project rather than helping on an existing one? Thank you very much for your help.

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prettyprint with IO
by Warren Harris 13 Apr '12

13 Apr '12

I wrote a parsec parser that does symbols lookups during the parsing process (ParsecT String Store IO a). Now I'd like to write a pretty printer that does the reverse. Unfortunately there doesn't appear to be a transformer version of Text.PrettyPrint.HughesPJ. Can anyone suggest a way to do this? Thanks, Warren

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I Need a Better Functional Language!
by Grigory Sarnitskiy 12 Apr '12

12 Apr '12

Hello! I've just realized that Haskell is no good for working with functions! First, what are 'functions' we are interested at? It can't be the usual set-theoretic definition, since it is not constructive. The constructive definition should imply functions that can be constructed, computed. Thus these are computable functions that should be of our concern. But computable functions in essence are just a synonym for programs. One could expect from a language that bears 'functional' as its characteristic to be able to do everything imaginable with functions. However, the only thing Haskell can do with functions is to apply them to arguments and to feed them as arguments, run in parallel (run and concatenate programs). Obviously, that's not all of the imaginable possibilities. One also can rewrite programs. And write programs that rewrite programs. And write programs that rewrite programs that rewrite the first programs and so on. But there is no such possibility in Haskell, except for introducing a DSL. So now I wonder, what are the languages that are functional in the sense above? With a reasonable syntax and semantics, thus no assembler. I guess Lisp might be of this kind, but I'm not sure. In addition, I'm not a fan of parentheses. What else? Pure? Mathematica? Maxima? Note, that the reflectivity is important.

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Is type class 'Addressable' already exists.
by 陈文龙 12 Apr '12

12 Apr '12

To get element in List,Map... in python's way. Python: > strMap["apple"] Haskell: > strMap # "apple" https://gist.github.com/2364395 {-# LANGUAGE TypeFamilies #-} module Addressable where import qualified Data.Map as M import Prelude class Addressable a where type Key a type Value a (#!) :: a -> Key a -> Value a (#) :: a -> Key a -> Maybe (Value a) instance Addressable [a] where type Key [a] = Int type Value [a] = a (#!) = (!!) xs # i | i < 0 = Nothing [] # _ = Nothing (x:_) # 0 = Just x (_:xs) # n = xs # (n-1) instance (Ord k) => Addressable (M.Map k v) where type Key (M.Map k v) = k type Value (M.Map k v) = v a #! i = a M.! i a # i = M.lookup i a main :: IO () main = do let strMap = M.fromList [("one","1"),("two","2"),("three","3")] let strList = ["1","2","3"] print $ strMap # "two" -- Just "2" print $ strMap #! "two" -- "2" print $ strList # 0 -- Just "1" print $ strList #! 0 -- "1" print $ strMap # "no-exist" -- Nothing print $ strList # 100 -- Nothing print $ strMap #! "no-exist" -- error print $ strList #! 100 -- error

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