January 2008 - Haskell

Announcing Djinn, version 2004-12-11, a coding wizard
by Lennart Augustsson 07 Apr '11

07 Apr '11

Howdy, y'all! I've written a small program that takes a (Haskell) type and gives you back a function of that type if one exists. It's kind of fun, so I thought I'd share it. It's probably best explained with a sample session. calvin% djinn Welcome to Djinn version 2005-12-11. Type :h to get help. # Djinn is interactive if not given any arguments. # Let's see if it can find the identity function. Djinn> f ? a->a f :: a -> a f x1 = x1 # Yes, that was easy. Let's try some tuple munging. Djinn> sel ? ((a,b),(c,d)) -> (b,c) sel :: ((a, b), (c, d)) -> (b, c) sel ((_, v5), (v6, _)) = (v5, v6) # We can ask for the impossible, but then we get what we # deserve. Djinn> cast ? a->b -- cast cannot be realized. # OK, let's be bold and try some functions that are tricky to write: # return, bind, and callCC in the continuation monad Djinn> type C a = (a -> r) -> r Djinn> returnC ? a -> C a returnC :: a -> C a returnC x1 x2 = x2 x1 Djinn> bindC ? C a -> (a -> C b) -> C b bindC :: C a -> (a -> C b) -> C b bindC x1 x2 x3 = x1 (\ c15 -> x2 c15 (\ c17 -> x3 c17)) Djinn> callCC ? ((a -> C b) -> C a) -> C a callCC :: ((a -> C b) -> C a) -> C a callCC x1 x2 = x1 (\ c15 _ -> x2 c15) (\ c11 -> x2 c11) # Well, poor Djinn has a sweaty brow after deducing the code # for callCC so we had better quit. Djinn> :q Bye. To play with Djinn do a darcs get http://darcs.augustsson.net/Darcs/Djinn or get http://darcs.augustsson.net/Darcs/Djinn/Djinn.tar.gz Then just type make. (You need a Haskell 98 implementation and some libraries.) And then start djinn. For the curious, Djinn uses a decision procedure for intuitionistic propositional calculus due to Roy Dyckhoff. It's a variation of Gentzen's LJ system. This means that (in theory) Djinn will always find a function if one exists, and if one doesn't exist Djinn will terminate telling you so. This is the very first version, so expect bugs. :) Share and enjoy. -- Lennart

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Haskell-mode 2.0
by Stefan Monnier 02 Feb '09

02 Feb '09

I have recently taken over maintainership of Haskell-mode, and after making a bunch of changes, I figured it would be a good idea to make a new release. You can find this new release at: http://www-perso.iro.umontreal.ca/~monnier/elisp/ If you think it should also be found at http://www.haskell.org/haskell-mode/, then please tell John Peterson to get back to me (my email to him seem to go straight to the bitbucket. John?). This release has several changes that have all been only lightly tested, especially w.r.t compatibility with various Emacsen. See appended the NEWS file that describes some of the notewirthy changes. Stefan Changes since 1.45: * keybindings C-c <char> have been replaced by C-c C-<char> so as not to collide with minor modes. * The following modules are now automatically activated without having to add anything to haskell-mode-hook: haskell-font-lock (just turn on global-font-lock-mode). haskell-decl-scan (just bind `imenu' to some key). * In recent Emacsen, haskell-doc hooks into eldoc-mode. * haskell-hugs and haskell-ghci are superceded by inf-haskell. * Indentation rules have been improved when using layout inside parens/braces. * Symbols like -> and \ can be displayed as actual arrows and lambdas. See haskell-font-lock-symbols. * Tweaks to the font-lock settings. Among other things paren-matching with things like \(x,y) should work correctly now. * New maintainer <monnier(a)gnu.org>.

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The real Monad Transformer
by Henning Thielemann 13 Nov '08

13 Nov '08

It was argued that people avoid Haskell because of terms from Category theory like 'Monad'. This problem can now be solved by a wrapper which presents all the WWW without monads! Start e.g. at http://saxophone.jpberlin.de/MonadTransformer?source=http%3A%2F%2Fwww%2Ehas… Of course the tool is written in Haskell, that is, Haskell helps solving problems which only exist because of Haskell. Bug reports and feature requests can be tracked at https://sourceforge.net/projects/parallelweb

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ANN: MacOSX - A library some Haskell users on OS X might find useful.
by Corey O'Connor 27 Feb '08

27 Feb '08

I've been working on integrating haskell code with some Objective-C/C++ Cocoa Mac OS X applications. Nothing fancy like a Haskell/Cocoa bridge. Just trying to get the build process smooth. The default cabal build system was incomplete to do this effectively;* Extending XCode was no good either. With some effort I created some Cabal build hooks to fix up the behavior of build on OS X and add support for packaging an executable into a ".app" package. That's not much, but I packaged it up, plus some extras, into a library in case other projects would like to use it: http://tothepowerofdisco.com/repo/HaskellLibraries/ Of course, this is all hackish and very incomplete. EG: * No fat binary support. I only have a PPC Mac and the only fat-binary process usable with GHC I know of requires executing the x86 GHC. * The build hook in MacOSX.Build will only work on the Cabal distributed with GHC 6.6.1 and *completely* replaces the standard GHC build hook. * GHC compiled to use the framework version of GMP installed to /Library/Frameworks is required. * The name is vague... Still, I've used it to add haskell support and replace XCode for building for 3 exisitng Cocoa applications. Maybe somebody else will find it useful as well. -- -Corey O'Connor * I neglected to make a good list of why the default Cabal build hook doesn't work.

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Announce: Yi 0.3
by Jean-Philippe Bernardy 31 Jan '08

31 Jan '08

Hello folks, I'm please to announce the 0.3 release of the Yi editor. Yi is a text editor written and extensible in Haskell. The long-term goal of the Yi project is to provide the editor of choice for Haskell programmers. In the meantime, we have fun by hacking an editor in a decent language :) Yi is not a finished product: this is a developer pre-release. However, Yi has become a lot more accessible than previously, so if you consider hacking on it, now might be a good time to take a look. Features * A purely functional editor core; * Keybindings written as parsers of the input; * Emacs and Vim emulations provided by default; * Vty, Gtk2Hs?, and (experimental) Cocoa frontends; * Embedding of GHC API for quick hacks and configuration. Links * release notes: http://code.google.com/p/yi-editor/wiki/ReleaseNotes0o3 * download: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/yi-0.3 * FAQ: http://haskell.org/haskellwiki/Yi/FAQ * homepage: http://haskell.org/haskellwiki/Yi * API documentation: http://code.haskell.org/yi/doc/ * check and report issues: http://code.google.com/p/yi-editor/issues/list * darcs repository: http://code.haskell.org/yi * get involved: mailto:yi-devel@googlegroups.com This release is brought to you by: Allan Clark, Andrew Birkett, Ben Moseley, Corey O'Connor, Daniel McAllansmith, Fraser Wilson, Gustav Munkby, Gwern Branwen, Jean-Philippe Bernardy, Jens Petersen, Massimiliano Gubinelli, Michael Maloney, Nicolas Pouillard, Paulo Tanimoto, Scott Williams, Thomas Schilling.

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2008 OCaml Summer Project
by Yaron Minsky 30 Jan '08

30 Jan '08

I hope this isn't deemed too off-topic for a Haskell list, since OCaml and Haskell are close relatives on good terms. In any case: I am pleased to announce the second OCaml Summer Project! The OSP is aimed at encouraging growth in the OCaml community by funding students over the summer to work on open-source projects in OCaml. We'll fund up to three months of work, and at the end of the summer, we will fly the participants out for a meeting in New York, where people will present their projects and get a chance to meet with other members of the OCaml community. The project is being funded and run by Jane Street Capital. Jane Street makes extensive use of OCaml, and we are excited about the idea of encouraging and growing the OCaml community. Our goal this year is to get both faculty and students involved. To that end, we will require joint applications from the student or students who will be working on the project, and from a faculty member who both recommends the students and will mentor them throughout the project. Each student will receive a grant of $5k/month for over the course of the project, and each faculty member will receive $2k/month. We expect students to treat this as a full-time commitment, and for professors to spend the equivalent of one day a week on the project. We will also award a prize for what we deem to be the most successful project. Special consideration will be given to projects that display real polish in the form of good documentation, robust build systems, and effective test suites. We'll announce more details about the prize farther down the line. If you'd like to learn more about the OSP and how to apply, you can look at our website here: http://ocamlsummerproject.com Please direct any questions or suggestions you have to osp(a)janestcapital.com. y -- Yaron Minsky <yminsky(a)janestcapital.com>

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Presentations at Dutch Functional Programming Day 2008
by Johan Jeuring 30 Jan '08

30 Jan '08

Most of the presentations at the Dutch Functional Programming Day 2008 are now available on-line: http://people.cs.uu.nl/johanj/FPDag2008/ All slides are in English. -- Johan

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PhD positions in Functional Programming at Chalmers in Sweden
by Koen Claessen 30 Jan '08

30 Jan '08

(apologies for multiple copies) ** please forward this to interested students ** PhD Positions in Functional Programming at the department of Computer Science and Engineering at Chalmers University of Technology, Sweden http://www.cs.chalmers.se/~koen/phdad.html Application deadline: March 11, 2008 Position starts: April 1, 2008 or September 1, 2008 The PhD student will join the research activities at our department in applications of functional programming, much of which concentrates on the design and application of Domain Specific Embedded Languages. Examples of our work are QuickCheck for specification-guided random testing, and Lava for hardware design and verification. Our group has also developed the award winning automated first-order logic reasoning tools Paradox and Equinox, which are both written in Haskell. There are advertised positions in two focus areas: 1. Development of the next generation of Paradox and Equinox, which involves inventing new programming techniques for building a modular, flexible automated reasoning tool, as well as developing novel automated reasoning algorithms. As new exciting applications for automated reasoning tools arise, new demands are placed on the reasoning tools, forcing changes in how they are designed and implemented. 2. Development of verification techniques for distributed systems implemented in the functional programming language Erlang. Methods here include QuickCheck-based testing, model checking and (automated) theorem proving techniques, and integration of these different techniques. There is a possibility of attacking real-world problems from our industrial partners. For more information, please look at: http://www.cs.chalmers.se/~koen/phdad.html Koen Claessen John Hughes

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School LERNET 2008 *** Deadline extension for registration ***
by Alberto Pardo 29 Jan '08

29 Jan '08

=================================================================== *** DEADLINE EXTENSION FOR REGISTRATION *** Call for Participation International Summer School on Language Engineering and Rigorous Software Development LERNET 2008, Piriapolis, Uruguay February 25 to March 1, 2008 http://www.fing.edu.uy/inco/eventos/lernet2008 email: lernet(a)fing.edu.uy *** NEW DEADLINE FOR REGISTRATION: February 4 *** *** DEADLINE FOR GRANT APPLICATION: January 31 *** =================================================================== The aim of the school is the dissemination of advanced scientific knowledge and the promotion of international contacts among scientists. The school is oriented to students and researchers working in computer science and interested in formal techniques for the design and construction of software systems and programming languages. The school is partially supported by the EU LerNet ALFA project (http://www.di.uminho.pt/lernet/) which implements a joint PhD programme on Software Design and Programming Language Engineering, based on a co-tutoring scheme and conformed by 6 european universities and 5 from Latin America. PROGRAM LERNET 2008 will consist of six courses: - Introduction to Type Theory Herman Geuvers (Radboud University Nijmegen, The Netherlands) - Theory and Applications of the PF-transform Jose Nuno Oliveira (University of Minho, Portugal) - Embedded Domain Specific Languages: Combinator Parsers Doaitse Swierstra (Utrecht University, The Netherlands) - Dependent Types at Work Peter Dybjer and Ana Bove (Chalmers University, Sweden) - Formal Programming Language Semantics with Inductive Types Yves Bertot (INRIA Sophia-Antipolis, France) - Verification Methods for Software Security and Correctness Gilles Barthe (INRIA Sophia-Antipolis, France) In addition, there will be some PhD sessions where students from the LerNet project will expose advances of their PhD thesis. VENUE LERNET 2008 will be held at Argentino Hotel (http://www.argentinohotel.com.uy) located in Piriápolis, a seaside city, 100 kms east from Montevideo. REGISTRATION To register, fill in the registration form at http://www.cs.chalmers.se/Cs/Research/Logic/LerNet08/registration.html The deadline for registration has been *extended*. The new deadline is February 4, 2008. FEES Details about the registration fees can be found in the school's webpage (http://www.fing.edu.uy/inco/eventos/lernet2008) GRANTS We may be able to offer a reduction in the value of the registration fee to a limited number of students. Priority will be given to students from Latin America. Details of the fee reduction application can be found in the school's webpage (http://www.fing.edu.uy/inco/eventos/lernet2008) The deadline for grant application is January, 31 2008. **Note that this deadline has not been extended**. SCHOOL ORGANISERS Luis Barbosa (Univerity of Minho, Portugal) Ana Bove (Chalmers University, Sweden) Alberto Pardo (Universidad de la República, Uruguay) Jorge Sousa Pinto (Univerity of Minho, Portugal) LOCAL ORGANISATION Alberto Pardo Luis Sierra Carlos Luna Instituto de Computación Facultad de Ingeniería Universidad de la República Montevideo, Uruguay FURTHER INFORMATION For further details on the school, visit the webpage http://www.fing.edu.uy/inco/eventos/lernet2008

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4th Haskell Hackathon, April 11-13 in Gothenburg, Sweden
by Björn Bringert 28 Jan '08

28 Jan '08

------------------------------------------------------------------------ Hac4 4th Haskell Hackathon April 11-13, 2008 Gothenburg, Sweden http://haskell.org/haskellwiki/Hac4 ------------------------------------------------------------------------ We are pleased to announce the 4th Haskell Hackathon! The event will be held over 3 days, April 11-13, at Chalmers University of Technology in Gothenburg, Sweden. The plan is to hack on Haskell infrastructure, tools, libraries and compilers. To attend please register, and get ready to hack those lambdas! Code to hack on: * Hackage * Cabal * Porting foreign libraries * Bug squashing * You decide! Before you attend, do start thinking and familiarizing yourself with 1 or 2 projects you wish to work on, to ensure no wasted effort during the Hackathon. A list of possible projects is available on the website. == Registration == We ask that you register you interest. Follow the instructions on the registration page: http://haskell.org/haskellwiki/Hac4/Register Once you've registered, do add your info to the attendees self-organizing page, http://haskell.org/haskellwiki/Hac4/Attendees if you are looking to share costs, or meet up prior to the hackathon, with other attendees. N.B. if you already expressed interest via the wiki, do confirm by registering `officially' anyway. == Important dates == Hackathon: April 11-13, 2008 == Organizers == Björn Bringert Thomas Schilling Lennart Kolmodin

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