- Haskell-Cafe - Haskell.org

A Java bytecode interpreter written in Haskell
by Erik Dominikus 26 May '16

26 May '16

(Please keep expectations low for now; this is just a weekend project.) I have written, in Haskell, something that aspires to be a Java Virtual Machine (but I don't call it a JVM yet as it doesn't fully comply with the spec). The code is available here: https://github.com/edom/haji This is similar to Frege [3], but while Frege aims to run a variant of Haskell on Java, this project tries the other direction: running a subset of Java on Haskell. Thanks. Best, Erik Some related stuffs: [1] https://github.com/MateVM/MateVM [2] https://hackage.haskell.org/package/hs-java [3] https://github.com/Frege/frege [4] https://wiki.haskell.org/GHC:FAQ#Why_isn.27t_GHC_available_for_.NET_or_on_t… [5] https://github.com/levans/Open-Quark

3 4

Interacting with Java in GHCVM
by Rahul Muttineni 26 May '16

26 May '16

Hi Haskell-Cafe, I've been working on a JVM backend for GHC [1] and I took some time to flesh out a design for the Java FFI [2] which will pretty much decide whether the project will be useful or not. I would love feedback from the community on how to improve the design or requests for important interop features that I have neglected. Thanks, Rahul Muttineni [1] http://github.com/rahulmutt/ghcvm [2] https://gist.github.com/rahulmutt/355505bce57c7c2cffd7d4cf5edddad4

4 8

Example of FunBind without wrapping AbsBind?
by Robin Palotai 26 May '16

26 May '16

I was playing with the AST's typechecked tree, and found some examples of the subject, but can't tell what is the rule for that to occur. It was a local binding. Do you have a hint and/or a minimal example? Thanks! Robin

1 0

ANN: new #haskell-atom channel, Atom setup doc
by Simon Michael 25 May '16

25 May '16

Hi all, Recently I helped a newcomer set up Haskell and Atom (the text editor/IDE - not the embedded systems DSL), and also for the first time succeeded in getting a "modern IDE experience" working with my own projects. I've saved my notes so far - I hope you'll also find them useful: https://github.com/simonmichael/haskell-atom-setup In the process I found some issues, looked for help in many places, and wished the #haskell-atom IRC channel existed. So I've started it: #haskell-atom on Freenode I'm an Emacs man, but I try all the available Haskell IDEs periodically. Atom is the first one where I've succeeded in getting inline error reporting working, and it's the only one I could recommend to a new programmer or a mainstream IDE lover right now. So I think this channel is worth having, and will grow. All welcome! Best, -Simon

2 2

1st CfP: IFL 2016 (28th Symposium on Implementation and Application of Functional Languages)
by publicityifl＠gmail.com 25 May '16

25 May '16

Hello, Please, find below the first call for papers for IFL 2016. Please forward these to anyone you think may be interested. Apologies for any duplicates you may receive. best regards, Jurriaan Hage Publicity Chair of IFL --- IFL 2016 - Call for papers 28th SYMPOSIUM ON IMPLEMENTATION AND APPLICATION OF FUNCTIONAL LANGUAGES - IFL 2016 KU Leuven, Belgium In cooperation with ACM SIGPLAN August 31 - September 2, 2016 https://dtai.cs.kuleuven.be/events/ifl2016/ Scope The goal of the IFL symposia is to bring together researchers actively engaged in the implementation and application of functional and function-based programming languages. IFL 2016 will be a venue for researchers to present and discuss new ideas and concepts, work in progress, and publication-ripe results related to the implementation and application of functional languages and function-based programming. Peer-review Following the IFL tradition, IFL 2016 will use a post-symposium review process to produce the formal proceedings. All participants of IFL 2016 are invited to submit either a draft paper or an extended abstract describing work to be presented at the symposium. At no time may work submitted to IFL be simultaneously submitted to other venues; submissions must adhere to ACM SIGPLAN's republication policy: http://www.sigplan.org/Resources/Policies/Republication The submissions will be screened by the program committee chair to make sure they are within the scope of IFL, and will appear in the draft proceedings distributed at the symposium. Submissions appearing in the draft proceedings are not peer-reviewed publications. Hence, publications that appear only in the draft proceedings are not subject to the ACM SIGPLAN republication policy. After the symposium, authors will be given the opportunity to incorporate the feedback from discussions at the symposium and will be invited to submit a revised full article for the formal review process. From the revised submissions, the program committee will select papers for the formal proceedings considering their correctness, novelty, originality, relevance, significance, and clarity. The formal proceedings will appear in the International Conference Proceedings Series of the ACM Digital Library. Important dates August 1: Submission deadline draft papers August 3: Notification of acceptance for presentation August 5: Early registration deadline August 12: Late registration deadline August 22: Submission deadline for pre-symposium proceedings August 31 - September 2: IFL Symposium December 1: Submission deadline for post-symposium proceedings January 31, 2017: Notification of acceptance for post-symposium proceedings March 15, 2017: Camera-ready version for post-symposium proceedings Submission details Prospective authors are encouraged to submit papers or extended abstracts to be published in the draft proceedings and to present them at the symposium. All contributions must be written in English. Papers must use the new ACM two columns conference format, which can be found at: http://www.acm.org/publications/proceedings-template For the pre-symposium proceedings we adopt a 'weak' page limit of 12 pages. For the post-symposium proceedings the page limit of 12 pages is firm. Authors submit through EasyChair: https://easychair.org/conferences/?conf=ifl2016 Topics IFL welcomes submissions describing practical and theoretical work as well as submissions describing applications and tools in the context of functional programming. If you are not sure whether your work is appropriate for IFL 2016, please contact the PC chair at tom.schrijvers(a)cs.kuleuven.be. Topics of interest include, but are not limited to: - language concepts - type systems, type checking, type inferencing - compilation techniques - staged compilation - run-time function specialization - run-time code generation - partial evaluation - (abstract) interpretation - metaprogramming - generic programming - automatic program generation - array processing - concurrent/parallel programming - concurrent/parallel program execution - embedded systems - web applications - (embedded) domain specific languages - security - novel memory management techniques - run-time profiling performance measurements - debugging and tracing - virtual/abstract machine architectures - validation, verification of functional programs - tools and programming techniques - (industrial) applications Peter Landin Prize The Peter Landin Prize is awarded to the best paper presented at the symposium every year. The honored article is selected by the program committee based on the submissions received for the formal review process. The prize carries a cash award equivalent to 150 Euros. Programme committee Chair: Tom Schrijvers, KU Leuven, Belgium - Sandrine Blazy, University of Rennes 1, France - Laura Castro, University of A Coru√±a, Spain - Jacques, Garrigue, Nagoya University, Japan - Clemens Grelck, University of Amsterdam, The Netherlands - Zoltan Horvath, Eotvos Lorand University, Hungary - Jan Martin Jansen, Netherlands Defence Academy, The Netherlands - Mauro Jaskelioff, CIFASIS/Universidad Nacional de Rosario, Argentina - Patricia Johann, Appalachian State University, USA - Wolfram Kahl, McMaster University, Canada - Pieter Koopman, Radboud University Nijmegen, The Netherlands - Shin-Cheng Mu, Academia Sinica, Taiwan - Henrik Nilsson, University of Nottingham, UK - Nikolaos Papaspyrou, National Technical University of Athens, Greece - Atze van der Ploeg, Chalmers University of Technology, Sweden - Matija Pretnar, University of Ljubljana, Slovenia - Tillmann Rendel, University of T√ºbingen, Germany - Christophe Scholliers, Universiteit Gent, Belgium - Sven-Bodo Scholz, Heriot-Watt University, UK - Melinda Toth, Eotvos Lorand University, Hungary - Meng Wang, University of Kent, UK - Jeremy Yallop, University of Cambridge, UK Venue The 28th IFL will be held in association with the Faculty of Computer Science, KU Leuven, Belgium. Leuven is centrally located in Belgium and can be easily reached from Brussels Airport by train (~15 minutes). The venue in the Arenberg Castle park can be reached by foot, bus or taxi from the city center. See the website for more information on the venue.

1 0

Dev/tools/git/Haskell role in London
by Don Stewart 25 May '16

25 May '16

https://donsbot.wordpress.com/2016/05/24/haskell-devtoolsgit-role-at-standa… I have a new role at SCB this time in the "Modelling Infrastructure" team to work on our Haskell-based continuous integration and testing system on top of git. This is a London role. More details in the linked post.

1 0

Stack build with GHC 8?
by David Turner 24 May '16

24 May '16

Hi, My name appears in the Stackage GHC 8 mega-issue [ https://github.com/fpco/stackage/issues/1476] and I'd like to upgrade my packages. I suspect it's just a case of relaxing the upper bound on base to <4.10 but I'd quite like to check that this does, in fact, work. However I'm not sure how to go about doing this since there don't yet seem to be any stackage snapshots that use GHC 8. What's the best way to get around this? Cheers, David

2 1

[ANNOUNCE] GHC 8.0.1 is available!
by Ben Gamari 23 May '16

23 May '16

=============================================== The Glasgow Haskell Compiler -- version 8.0.1 =============================================== The GHC developers are very pleased to announce the release of the first new super-major version of our Haskell compiler in six years, GHC 8.0.1. This release features dozens of exciting developments including, * A more refined interface for implicit call-stacks, allowing libraries to provide more helpful runtime error messages to users * The introduction of the DuplicateRecordFields language extension, allowing multiple record types to declare fields of the same name * Significant improvements in error message readability and content, including facilities for libraries to provide custom error messages, more aggressive warnings for fragile rewrite rules, and more helpful errors for missing imports * A rewritten and substantially more thorough pattern match checker, providing more precise exhaustiveness checking in GADT pattern matches * More reliable debugging information including experimental backtrace support, allowing better integration with traditional debugging tools * Support for desugaring do-notation to use Applicative combinators, allowing the intuitive do notation to be used in settings which previously required the direct use of Applicative combinators * The introduction of Strict and StrictData language extensions, allowing modules to be compiled with strict-by-default evaluation of bindings * Great improvements in portability, including more reliable linking on Windows, a new PPC64 code generator, support for the AIX operating system, unregisterised m68k support, and significant stabilization on ARM targets * A greatly improved user's guide, with beautiful and modern PDF and HTML output * Introduction of type application syntax, reducing the need for proxies * More complete support for pattern synonyms, including record pattern synonyms and the ability to export patterns "bundled" with a type, as you would a data constructor * Support for injective type families and recursive superclass relationships * An improved generics representation leveraging GHC's support for type-level literals * The TypeInType extension, which unifies types and kinds, allowing GHC to reason about kind equality and enabling promotion of more constructs to the type level * ...and more! A more thorough list of the changes included in this release can be found in the release notes, https://downloads.haskell.org/~ghc/8.0.1/docs/html/users_guide/8.0.1-notes.… As always, we have collected various points of interest for users of previous GHC releases on the GHC 8.0 migration page, https://ghc.haskell.org/trac/ghc/wiki/Migration/8.0 Please let us know if you encounter anything missing or unclear on this page. This release is the culmination of nearly eighteen months of effort by over one hundred contributors. We'd like to thank everyone who has contributed code, bug reports, and feedback over the past year. It's only because of their efforts that GHC continues to evolve. How to get it ~~~~~~~~~~~~~ Both the source tarball and binary distributions for a wide variety of platforms are available at, http://www.haskell.org/ghc/ Background ~~~~~~~~~~ Haskell is a standardized lazy functional programming language. The Glasgow Haskell Compiler (GHC) is a state-of-the-art programming suite for Haskell. Included is an optimising compiler generating efficient code for a variety of platforms, together with an interactive system for convenient, quick development. The distribution includes space and time profiling facilities, a large collection of libraries, and support for various language extensions, including concurrency, exceptions, and foreign language interfaces. GHC is distributed under a BSD-style open source license. Supported Platforms ~~~~~~~~~~~~~~~~~~~ The list of platforms we support, and the people responsible for them, can be found on the GHC wiki http://ghc.haskell.org/trac/ghc/wiki/Platforms Ports to other platforms are possible with varying degrees of difficulty. The Building Guide describes how to go about porting to a new platform: http://ghc.haskell.org/trac/ghc/wiki/Building Developers ~~~~~~~~~~ We welcome new contributors. Instructions on getting started with hacking on GHC are available from GHC's developer site, http://ghc.haskell.org/trac/ghc/ Community Resources ~~~~~~~~~~~~~~~~~~~ There are mailing lists for GHC users, develpoers, and monitoring bug tracker activity; to subscribe, use the web interfaces at http://mail.haskell.org/cgi-bin/mailman/listinfo/glasgow-haskell-users http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-tickets There are several other Haskell and GHC-related mailing lists on www.haskell.org; for the full list, see https://mail.haskell.org/cgi-bin/mailman/listinfo Some GHC developers hang out on the #ghc and #haskell of the Freenode IRC network, too: http://www.haskell.org/haskellwiki/IRC_channel Please report bugs using our bug tracking system. Instructions on reporting bugs can be found here: http://www.haskell.org/ghc/reportabug

5 4

Help moving a bounds check into a case branch
by David Feuer 23 May '16

23 May '16

Sorry for the terrible subject line, but I'm a but stuck here. A couple days ago I overhauled Data.Sequence.splitAt, greatly improving its performance. You can see the new implementation at https://github.com/haskell/containers/blob/e8b1f664a631e3795dfd14f2d8c2b39c… . There's one spot where I'm still stuck, however. Much like the original implementation, I check that the splitting index is before the end of the sequence (to ensure correctness). I go further, in fact, checking that the splitting index is positive, in order to avoid allocating a new tree-top in a trivial split. Logically, this check should be moved into the Deep case branch in splitTreeE, to avoid pattern matching on the top of the tree twice and performing redundant comparisons. However, when I make that move, the split/append benchmark gets worse. When I looked at the Core, it seemed that I confused GHC somehow. I ended up with a join point taking an extra argument that it totally ignored. I can fix that benchmark by marking the splitTreeMiddleE function INLINE, but then the zipWith benchmark went screwy. Unless I can get non-fragile results, I'm just going to accept the redundant case match. If anyone has any ideas, please let me know. Thanks, David Feuer

1 0

Re: [Haskell-cafe] TDNR without new operators or syntax changes
by Jeremy . 23 May '16

23 May '16

Yes, that it indeed was I meant. AntC seems to be replying to a much more complicated/invasive proposal than what I had intended, apologies if I wasn't clear. (I see in retrospect that I may have misunderstood the original TDNR proposal, understandably leading to confusion.) 1. If the compiler encounters a term f a, and there is more than one definition for f in scope (after following all of the usual rules for qualified imports); 2. And exactly one of these definitions matches the type of a (or the expected type of f if given); 3. Then this is the definition to use. That is all, although point 2 could be extended to consider the return type of f or other arguments as well. Even with the extension on, it would have no effect on programs which compile without it. This has nothing to do with ORF, which relies on magic type classes (although there is some overlap in what it can achieve). The primary use-case I had in mind is disambiguating name clashes between local and/or unqualified imports. Cross-posting to cafe and libraries as this doesn't seem to have attracted a lot of interest in users. Maybe it's just a boring proposal, maybe I didn't post it to the right list.

3 2