- Haskell-Cafe - Haskell.org

Type safety in foreign pointer
by Mauricio 15 Oct '08

15 Oct '08

Hi, I'm wrapping a library where functions take as parameters pointers to a few standard structs (as, well, all C libraries). I would like to ensure that only pointers of correct structs are passed to those functions. What is the "Haskell way" to do that? My idea is to do something like this: newtype SomeStruct = SomeStruct () and then foreign import ccall "my_function" myfunction :: Ptr SomeStruct -> IO int Is that the proper way to do that? Thanks, Maurício

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ICFP09: Call for Workshop Proposals
by Matthew Fluet (ICFP Publicity Chair) 15 Oct '08

15 Oct '08

CALL FOR WORKSHOP PROPOSALS ICFP 2009 14th ACM SIGPLAN International Conference on Functional Programming 31st August - 2nd September, 2009 Edinburgh, Scotland http://www.icfpconference.org/icfp2009 The 14th ACM SIGPLAN International Conference on Functional Programming will be held in Edinburgh, Scotland from 31st August to 2nd September 2009. ICFP provides a forum for researchers and developers to hear about the latest work on the design, implementations, principles, and uses of functional programming. Proposals are invited for workshops to be affiliated with ICFP 2009 and sponsored by SIGPLAN. These workshops should be more informal and focused than ICFP itself, include sessions that enable interaction among the workshop attendees, and be fairly low cost. The preference is for one-day workshops, but other schedules can also be considered. The workshops themselves will be held between August 30th and September 5th, as capacity allows. ---------------------------------------------------------------------- Submission details Deadline for submission: 19th November 2008 Notification of acceptance: 17th December 2008 Prospective workshop organisers are invited to submit a completed workshop proposal form in plain text format to the ICFP 2009 workshop co-chairs (Chris Stone and Mike Sperber), via email to icfp09-workshops at cs.hmc.edu by 19th November 2008. Please note that this is a firm deadline. Organisers will be notified if their proposal is accepted by 17th December 2008, and if successful are required to produce a final report after the workshop has taken place that is suitable for publication in SIGPLAN Notices. The proposal form is available at: http://www.icfpconference.org/icfp2009/workshops/icfp09-workshops-form.txt Further information about SIGPLAN sponsorship is available at: http://acm.org/sigplan/sigplan_workshop_proposal.htm ---------------------------------------------------------------------- Selection committee The workshop proposals will be evaluated by a committee comprising the following members of the ICFP 2009 organising committee, together with the members of the SIGPLAN executive committee. Chris Stone Harvey Mudd College Workshops co-chair Mike Sperber DeinProgramm Workshops co-chair Graham Hutton University of Nottingham General Chair Andrew Tolmach Portland State University Program Chair ---------------------------------------------------------------------- Further information Any queries regarding ICFP 2009 workshop proposals should be addressed to the workshops co-chairs (Chris Stone and Mike Sperber), via email to icfp09-workshops at cs.hmc.edu

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I do not want to be a bitch, but ghc-6.8.3 and haskell binary policy are really horrible.
by Magicloud 15 Oct '08

15 Oct '08

1. I cannot install ghc-6.8.3 in my box until I found the old runable binary. 2. After I installed cabal, and upgraded, ghc-6.8.3 cannot rebuild itself. Because its libraries are conflict with the ones upgraded by cabal. 3. Sometimes, ghc just ignore some libs, because it does not meet its dependencies. Well, ghc does not even tell me. It knows what I want? 4. I use cabal, thinking it would make dependencies installation easier for me. Well it does not, once an error happened, nothing would work since. I cannot even remove the broken lib. 5. No more needed. The above ones, which are important enough to drive me crazy.

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Multi-line string literals are both easy /and/ elegant in Haskell
by Matt Morrow 15 Oct '08

15 Oct '08

The new QuasiQuotes extension arriving with ghc 6.10 is very exciting, and handling multi-line string literals is like stealing candy from a baby. ;) ----------------------------------------------------------------------------- -- Here.hs module Here (here) where import Language.Haskell.TH.Quote import Language.Haskell.TH.Syntax import Language.Haskell.TH.Lib here :: QuasiQuoter here = QuasiQuoter (litE . stringL) (litP . stringL) ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- -- There.hs {-# LANGUAGE QuasiQuotes #-} module Main where import Here (here) main = putStr [$here| Shall I say, I have gone at dusk through narrow streets And watched the smoke that rises from the pipes Of lonely men in shirt-sleeves, leaning out of windows? I should have been a pair of ragged claws Scuttling across the floors of silent seas. |] ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- [m@ganon a]$ ghc -O2 --make There.hs [1 of 2] Compiling Here ( Here.hs, Here.o ) [2 of 2] Compiling Main ( There.hs, There.o ) Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. Loading package syb ... linking ... done. Loading package array-0.2.0.0 ... linking ... done. Loading package packedstring-0.1.0.1 ... linking ... done. Loading package containers-0.2.0.0 ... linking ... done. Loading package pretty-1.0.1.0 ... linking ... done. Loading package template-haskell ... linking ... done. Linking There ... [m@ganon a]$ ./There Shall I say, I have gone at dusk through narrow streets And watched the smoke that rises from the pipes Of lonely men in shirt-sleeves, leaning out of windows? I should have been a pair of ragged claws Scuttling across the floors of silent seas. [m@ganon a]$ -----------------------------------------------------------------------------

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ANNOUNCE: Salsa: A .NET Bridge for Haskell
by Andrew Appleyard 15 Oct '08

15 Oct '08

I'd like to announce the first release of Salsa, an experimental Haskell library that allows Haskell programs to access .NET libraries. Here's a taste: > type Hello.hs import Foreign.Salsa import Bindings main = withCLR $ do _Console # _writeLine ("Hello .NET World!") > type Hello.imports System.Console: WriteLine > msbuild > .\hello Hello .NET World! Salsa operates by loading the .NET runtime into your Haskell process and using the FFI (and run-time code generation) to marshall calls between the .NET and Haskell runtimes. It includes a code generator and a type-level library (which uses type families) to provide type-safe access to .NET libraries in Haskell with C#-style method overload resolution and implicit conversions. The adventurous can find version 0.1.0.1 of Salsa on Hackage [1], the darcs repository on code.haskell.org [2], and some (limited) documentation on the Haskell wiki [3]. The library is experimental and by no means complete (refer to the wiki page [3] for some of its limitations). Be prepared to end up with incomprehensible error messages and/or a broken compiler! :-) At the moment you'll need Windows, GHC 6.8, and version 3.5 of the .NET Framework to use it. Have fun! [1] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Salsa [2] http://code.haskell.org/Salsa [3] http://haskell.org/haskellwiki/Salsa -- Andrew

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How to specify multiple fonts for xmobar?
by Magicloud 15 Oct '08

15 Oct '08

Hi, I am using xmonad + xmobar. And I am using sgi screen font. But sometimes I need to display CJK characters, which need another font. In gtk2 software, this is OK. I just specify the screen font for ascii. It can auto-choose a CJK font. Everything looks fine, maybe not pretty. While, xmobar does not auto-choose a CJK font, if I just specify screen font for ascii, it displays CJK characters in blank. How to fix this?

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Foreign.Marshal.Error.void
by Mauricio 15 Oct '08

15 Oct '08

Hi, Wouldn't it be nice if we had something like 'void' in Foreign.Marshal.Error in standard monad functions, so that we could use it instead of, for instance, mapM_ or sequence_? Best, Maurício

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There is something wrong with hprotoc-0.3.1 package.
by Magicloud 15 Oct '08

15 Oct '08

Hi, I wanted to install this package. Well, Building hprotoc-0.3.1... ... [3 of 7] Compiling Text.ProtocolBuffers.ProtoCompile.Parser ... Text/ProtocolBuffers/ProtoCompile/Parser.hs:48:0: Type synonym `GenParser' should have 2 arguments, but has been given 1 In the type synonym declaration for `P' And it just stopped here.

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There is something wrong in derive-0.1.2 package.
by Magicloud 14 Oct '08

14 Oct '08

Hi, I wanted to install it with cabal. Well $ cabal install derive Resolving dependencies... cabal: Couldn't read cabal file "./derive/0.1.2/derive.cabal" As I traced a little, it seemed that line: 'build-depends: base == 4.*, syb' was wrong.

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[ANN] Haskell Cheatsheet v1.0
by Justin Bailey 14 Oct '08

14 Oct '08

All, I've created a "cheat sheet" for Haskell. It's a PDF that tries to summarize Haskell 98's syntax, keywords and other language elements. It's currently available on hackage[1]. Once downloaded, unpack the archive and you'll see the PDF. A literate source file is also included. If you install with "cabal install cheatsheet", run "cheatsheet" afterwards and the program will tell you where the PDF is located. The audience for this document is beginning to intermediate Haskell programmers. I found it difficult to look up some of the less-used syntax and other language stumbling blocks as I learned Haskell over the last few years, so I hope this document can help others in the future. This is a beta release (which is why I've limited the audience by using hackage) to get feedback before distributing the PDF to a wider audience. With that in mind, I welcome your comments or patches[2]. Justin [1] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/CheatSheet [2] git://github.com/m4dc4p/cheatsheet.git

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