- Haskell-Cafe - Haskell.org

Import hiding module
by amindfv＠gmail.com 02 May '15

02 May '15

It's possible to write e.g. module A (module A.B, x) where To reexport everything from A.B And we can import A hiding (x) Is there a way to also import A hiding (module A.B) ? Thanks

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Swapping type arguments
by Alexey Uimanov 01 May '15

01 May '15

This question probably asked already. I have a type data T m b a = T (m (b, a)) and it should be instance of `Bifunctor` and `MonadTrans` same time. But there is a problem: instance Bifunctor (T m) is ok, but instance MonadTrans (T ... is not, because first argument is `m` but we need `b`. Type can be rewritten like data T b m a = T (m (b, a)) and instance of MonadTrans is ok: instance MonadTrans (T b) but how to define Bifunctor? instance Bifunctor (T ... I did not found how to workaround this. Is there any type magic for such cases?

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Haskell Weekly News
by Kim-Ee Yeoh 01 May '15

01 May '15

*Top Picks:* - Haskell wins a bumper crop of 18 accepted Google Summer of Code proposals <http://www.reddit.com/r/haskell/comments/342rvp/google_summer_of_code_18_pr…>. Mentor offers total 44, another thumpin' sign of life. Kudos to Edward Kmett, Johan Tibell, Shachaf Ben-Kiki, and Gershom Bazerman. Gloria Haskella sine labore nulla. - Reddit Haskell celebrates <http://www.reddit.com/r/haskell/comments/33wnf1/20k_rhaskell_subscribers_ni…> 20k subscribers. It's the 7th largest PL community on reddit <https://www.reddit.com/r/programming/wiki/faq#wiki_what_language_reddits_ar…> after python, javascript, java, php, ruby, c++, in that order. - Matthew Griffith <http://mechanical-elephant.com/thoughts/2015-04-20-becoming-productive-in-h…> migrates away from Python: "I do most of my web prototyping in Haskell now." A journey vividly logged and much loved on Hacker News <https://news.ycombinator.com/item?id=9431944>. And also on Proggit <http://www.reddit.com/r/programming/comments/33oyx9/becoming_productive_in_…> and Reddit Haskell <http://www.reddit.com/r/haskell/comments/33mnlc/becoming_productive_in_hask…> . - A web developer migrates away from Rails to Haskell and explains on HN the 10x advantage <https://news.ycombinator.com/item?id=9419601#up_9420448> he reaps. - Fancy Python in Haskell dress? Check out Dogelang <http://pyos.github.io/dg/>, charmingly defiant: "With Haskell's syntax but none of its type system, dg is the best way to make fans of static typing shut up already." Proggit kibbitzing here <http://www.reddit.com/r/programming/comments/33kleg/dg_its_a_python_no_its_…>, HN there <https://news.ycombinator.com/item?id=9432383>. - Caio Rordrigues copiously illustrates <https://github.com/caiorss/Functional-Programming> Haskell programming. Pretty: a tax bracket tool <https://github.com/caiorss/Functional-Programming#tax-brackets> and a coffee shop Point-of-Sale DSL <https://github.com/caiorss/Functional-Programming#small-dsl-domain-specific…>. It's almost a whole book! - Christian Marie starts the ball rolling on library cheatsheets <https://github.com/anchor/haskell-cheat-sheets/> to guide your way through the jungle of hackage. Moar, moar! <http://www.reddit.com/r/haskell/comments/33sc98/haskell_cheat_sheets_for_co…> - Got a C library you'd love Haskell bindings for? Remember Ian Ross and his new C2HS release <http://haskell.1045720.n5.nabble.com/Haskell-Weekly-News-td5768107.html>? Well, Ian's happy <http://haskell.1045720.n5.nabble.com/Tutorial-Ideas-td5808049.html> to do it for you. Provisos <http://www.skybluetrades.net/blog/posts/2015/04/27/c2hs-tutorial-request.ht…> apply. - Olle Fredriksson announces a combinator-based Earley parsing library <https://github.com/ollef/Earley> which accepts context-free but not context-sensitive (monadic parsing) grammars. Discussion <https://www.reddit.com/r/haskell/comments/33l9cr/ann_earley_parsing_library/> reveals that "one enormously important difference for this library is that it reports all possible parses." - Another Lennart, last name Spitzner, creates another genie that turns type signatures into programs. Unlike Djinn, Exference <http://haskell.1045720.n5.nabble.com/ANN-exference-a-different-djinn-td5807…> makes no promises over termination. "Your wish is my command even at the expense of closure." - Like Agda? You can now enjoy the hole-driven development style in Haskell, brought to you courtesy of Mote by Izaak Meckler <https://github.com/imeckler/mote>. Discussion here <https://www.reddit.com/r/haskell/comments/33v4nm/ann_mote_a_tool_bringing_h…> . <http://tomassetti.me/an-erd-web-server-generation-entity-diagrams-from-a-te…> - Federico Tomassetti <http://tomassetti.me/an-erd-web-server-generation-entity-diagrams-from-a-te…> creates a web-based interface to Andrew Gallant's erd tool <https://github.com/BurntSushi/erd>. Entity-Relationship Diagrams (ERD) come from the database world and help visualize {one,many} to {one,many} relationships. Federico's web app enables him to use erd everywhere without having to install the tool chain multiple times. - Mark Dominus gives a beginner spin <http://blog.plover.com/prog/haskell/monad-search.html> to the chestnut of SEND + MORE = MONEY <https://en.wikipedia.org/wiki/Verbal_arithmetic>. This puzzle site <http://programmingpraxis.com/2012/07/31/send-more-money-part-1/> has comparisons with other languages. - Got a number system? Flip it into a data structure <https://www.fpcomplete.com/user/edwardk/fibonacci/leonardo>. Re-flip it into an efficient search algorithm <https://www.fpcomplete.com/user/edwardk/fibonacci/search>. Edward Kmett shows you how. Respective discussion here <http://www.reddit.com/r/haskell/comments/342s31/edward_kmett_leonardo_rando…> and here <http://www.reddit.com/r/haskell/comments/346b6t/edward_kmett_openended_fibo…> . *In Memoriam* - A key founder of Haskell, Professor Paul Hudak, completed <http://yaledailynews.com/blog/2015/04/30/hudak-spirited-saybrugian-and-cs-p…> his end-of-life plan <http://www.caringbridge.org/visit/hudak/journal/view/id/5538f5cea589b4216c0…> after a five-year encounter with leukemia. He stays <https://news.ycombinator.com/item?id=9431017> in the thoughts <https://news.ycombinator.com/item?id=9465999> of all <http://www.reddit.com/r/haskell/comments/33oe4b/holding_on_and_letting_go/> who cherish <http://www.reddit.com/r/haskell/comments/34exz3/prof_hudak_passed_away_last…> his gifts <http://www.reddit.com/r/programming/comments/34f19q/paul_hudak_creator_of_h…> from the heart. *Quotes of the Week* - A type system flattens the cost of change curve <http://www.agilemodeling.com/essays/costOfChange.htm>. -- Chad Austin <http://chadaustin.me/2015/04/the-long-term-problem-with-dynamically-typed-l…> - The MLs and Haskell remind me of Brian Eno's line about how the first Velvet Underground album only sold 30,000 copies, but "everyone who bought one of those 30,000 copies started a band". -- Source <https://news.ycombinator.com/item?id=9431944#up_9437017> - On the value of Haskell <https://news.ycombinator.com/item?id=9445968#up_9448988>: I find I'm able to accomplish tasks which would otherwise be beyond my skill and intelligence. For example, even though C was the first language I learned, I can't imagine writing a parser in C after discovering the simplicity & readability of monadic parsing in Haskell. - Haskell's level of abstraction is so crazy that they can actually swap out their entire I/O system for another one without changing any application interfaces, this one blew my mind, it's the change that makes GHC 7.8 run the Warp webserver twice as fast. ... All of this without changing a line in Warp, they just transparently made every traditional Haskell use modern I/O principles. Academics man, they're smart ;) -- Source <https://news.ycombinator.com/item?id=9419601#up_9432564> - An old man loved is winter with flowers. -- Edgar Z. Friedenberg *Cool Beans of the Week* - Ravi Chugh and his fine team at U. Chicago just concluded stateside's first ever FRP-based FP course for undergrads using Elm. Check out the student projects <https://www.classes.cs.uchicago.edu/archive/2015/winter/22300-1/Showcase.ht…> for inspiration on FRP architecture. Over in Bonn, Janis Voigtländer also gave such a course <https://groups.google.com/d/msg/elm-discuss/Qjs6sp3lZq0/8aa5bvYcdDYJ> that completed this year. Paul's legacy lives on. p.s. Coming soon: Cabal Hell -- Kim-Ee

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[TFP'15] call for participation
by Peter Achten 01 May '15

01 May '15

----------------------------- L A S T C A L L F O R P A R T I C I P A T I O N ----------------------------- ======== TFP 2015 =========== 16th Symposium on Trends in Functional Programming June 3-5, 2015 Inria Sophia Antipolis, France http://tfp2015.inria.fr/ The symposium on Trends in Functional Programming (TFP) is an international forum for researchers with interests in all aspects of functional programming, taking a broad view of current and future trends in the area. It aspires to be a lively environment for presenting the latest research results, and other contributions (see below). Authors of draft papers will be invited to submit revised papers based on the feedback receive at the symposium. A post-symposium refereeing process will then select a subset of these articles for formal publication. The selected revised papers will be published as a Springer Lecture Notes in Computer Science (www.springer.com/lncs) volume. TFP 2015 will be the main event of a pair of functional programming events. TFP 2015 will be accompanied by the International Workshop on Trends in Functional Programming in Education (TFPIE), which will take place on June 2nd. The TFP symposium is the heir of the successful series of Scottish Functional Programming Workshops. Previous TFP symposia were held in * Edinburgh (Scotland) in 2003; * Munich (Germany) in 2004; * Tallinn (Estonia) in 2005; * Nottingham (UK) in 2006; * New York (USA) in 2007; * Nijmegen (The Netherlands) in 2008; * Komarno (Slovakia) in 2009; * Oklahoma (USA) in 2010; * Madrid (Spain) in 2011; * St. Andrews (UK) in 2012; * Provo (Utah, USA) in 2013; * and in Soesterberg (The Netherlands) in 2014. For further general information about TFP please see the TFP homepage. (http://www.tifp.org/) == INVITED SPEAKERS == TFP is pleased to announce talks by the following two invited speakers: * Laurence Rideau is a researcher at INRIA and is interested in the semantics of programming languages , the formal methods, and the verification tools for programs and mathematical proofs. She participated in the beginnings of the Compcert project (certified compiler), and is part of the Component Mathematical team in the MSR-INRIA joint laboratory, who performed the formalization of the Feit-Thompson theorem successfully. Thirty years ago, computers barged in mathematics with the famous proof of the Four Color Theorem. Initially limited to simple calculation, their role is now expanding to the reasoning whose complexity is beyond the capabilities of most humans, as the proof of the classification of finite simple groups. We present our large collaborative adventure around the formalization of the Feit-Thompson theorem (http://en.wikipedia.org/wiki/Feit%E2%80%93Thompson_theorem) that is a first step to the classification of finite groups and that uses a palette of methods and techniques that range from formal logic to software (and mathematics) engineering. * Anil Madhavapeddy == SCOPE == The symposium recognizes that new trends may arise through various routes. As part of the Symposium's focus on trends we therefore identify the following five article categories. High-quality articles are solicited in any of these categories: Research Articles: leading-edge, previously unpublished research work Position Articles: on what new trends should or should not be Project Articles: descriptions of recently started new projects Evaluation Articles: what lessons can be drawn from a finished project Overview Articles: summarizing work with respect to a trendy subject Articles must be original and not simultaneously submitted for publication to any other forum. They may consider any aspect of functional programming: theoretical, implementation-oriented, or experience-oriented. Applications of functional programming techniques to other languages are also within the scope of the symposium. Topics suitable for the symposium include: Functional programming and multicore/manycore computing Functional programming in the cloud High performance functional computing Extra-functional (behavioural) properties of functional programs Dependently typed functional programming Validation and verification of functional programs Debugging and profiling for functional languages Functional programming in different application areas: security, mobility, telecommunications applications, embedded systems, global computing, grids, etc. Interoperability with imperative programming languages Novel memory management techniques Program analysis and transformation techniques Empirical performance studies Abstract/virtual machines and compilers for functional languages (Embedded) domain specific languages New implementation strategies Any new emerging trend in the functional programming area If you are in doubt on whether your article is within the scope of TFP, please contact the TFP 2015 program chair, Manuel Serrano. == BEST PAPER AWARDS == To reward excellent contributions, TFP awards a prize for the best paper accepted for the formal proceedings. TFP traditionally pays special attention to research students, acknowledging that students are almost by definition part of new subject trends. A student paper is one for which the authors state that the paper is mainly the work of students, the students are listed as first authors, and a student would present the paper. A prize for the best student paper is awarded each year. In both cases, it is the PC of TFP that awards the prize. In case the best paper happens to be a student paper, that paper will then receive both prizes. == SPONSORS == TFP is financially supported by Erlang Solutions. == PROGRAM == Please find the program at: http://tfp2015.inria.fr/program/ The program features two invited talks by Laurence Rideau and Anil Madhavapeddy and one comprehensive Dart tutorial by Florian Loitsch. == IMPORTANT DATES == Registration: May 4, 2015 TFP Symposium: June 3-5, 2015 == PROGRAM COMMITTEE == Janis Voigtländer University of Bonn, DE Scott Owens University of Kent, UK Neil Sculthorpe Swansea University, UK Colin Runciman University of York, UK Manuel Serrano Inria (PC chair), FR Rinus Plasmeijer University of Nijmegen, NL Tomas Petricek University of Cambridge, UK Marco T. Morazan Seton Hall University, USA Wolfgang De Meuter Vrije Universiteit Brussel, BE Michel Mauny Ensta ParisTech, FR Sam Lindley The University of Edinburgh, UK Daan Leijen Microsoft, USA Jurriaan Hage Utrecht University, NL Andy Gill University of Kansas, USA Thomas Gazagnaire University of Cambrige, UK Lars-Ake Fredlund Universidad Politécnica de Madrid, ES Jean-Christophe Filliatre Université Paris Sud Orsay, FR Marc Feeley Université de Montréal, CA Olaf Chitil University of Kent, UK Edwin Brady University of St Andrews, UK

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Roles, GND, Data.Coerce
by David Terei 30 Apr '15

30 Apr '15

All, An issue that came up with GHC 7.8 was the design of Roles and Data.Coerce, with it's ability to break module abstractions by default, requiring programmers adopt explicit role annotations to enforce some types of invariants for abstract data types. Because of this issue, as of now, GND & Data.Coerce are still disabled in Safe Haskell. We'd like to change this but need feedback from everyone. I've written up a wiki page with lots of information on the issue: https://ghc.haskell.org/trac/ghc/wiki/SafeRoles Please read, it has information on how Roles work, the problem it raises and subtleties in the current system. Possible paths forward are also there, but I'll include below. Please be aware that this discussion is about Roles in general, not specifically how when using -XSafe. Ideally we'd come up with a solution that works regardless of if using Safe Haskell or not. I personally like option (3), although it isn't clear to me how hairy the implementation would be. == Possible Paths Forward for Roles == 1) Do Nothing -- Keep Roles & GND unchanged, keep them unsafe in Safe Haskell. 2) Accept as Safe -- Keep Roles & GND unchanged, accept them as safe in Safe Haskell and warn users that they neednominal role annotations on ADTs. 3) In-scope constructor restriction for lifting instances -- The newtype constructor restriction for unwrapping instances could be extended to both data types, and the lifting instances of Data.Coerce. This is, GND & Coercing under a type constructor is allowed if (a) all involved constructors are in scope, or (b) the constructors involved have been explicitly declared to allow coercion without them being in scope. I.e., (b) allows library authors to opt-into the current GHC behavior. This would require new syntax, probably just an explicit deriving Coercible statement. 4) Change default role to nominal -- This will prioritize safety over GND, and the belief is that it may break a lot of code. Worse, that it will be an ongoing tax as role annotations will be needed to enable GND. 5) Nominal default when constructors aren't exported -- When a module doesn't export all the constructors of a data type, then the type parameters of the data type should default to nominal. This heuristic seems to capture somewhat the intention of the user, but given the practice of defining an Internal module that exports everything, it seems of limited use. 6) Nominal default in future -- Add a new extension, SafeNewtypeDeriving that switches the default role to nominal, but continue to provide a deprecated GND extension to help with the transition. The claims in support of representational roles as default though believe that nominal by default has an ongoing, continuous tax, not just a transition cost. So it isn't clear that any scheme like this satisfies that argument. 7) Safe Haskell Specific -- Many of the above approaches could be adopted in a Safe Haskell specific manner. This isn't ideal as it makes safe-inference harder and Safe Haskell less likely to remain viable going forward. Richard suggests one such idea. == The belief by many people seems to be that (4) and (6) would be too much of burden. I'd like to avoid (7) if possible. It isn't clear to me if (7) ends up better than (2). I'm going to try to setup some infastructure for compiling Hackage so that we can measure how impactful these changes would be. Cheers, David

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dependent types, singleton types....
by Nicholls, Mark 30 Apr '15

30 Apr '15

Can someone check my answer (no I'm not doing an assessment...I'm actually learning stuff out of interest!) working through https://www.fpcomplete.com/user/konn/prove-your-haskell-for-great-safety/de… still there is a section about singleton types and the exercise is "Exercise: Define the binary tree type and implement its singleton type." Ok, I think I'm probably wrong....a binary tree is something like... > data BTree a = Leaf | Branch a (BTree a) (BTree a) With DataKind My logic goes... Leaf is an uninhabited type, so I need a value isomorphic to it.... Easy? > data SBTree a where > SLeaf :: SBTree Leaf Things like Branch Integer Leaf (Branch String Leaf Leaf) Are uninhabited...so I need to add > SBranch :: (a :: *) -> (SBTree (b :: BTree *)) -> (SBTree (c :: BTree *)) -> SBTree (Branch a b c) ? It compiles...but....is it actually correct? Things like > y = SBranch (SS (SS SZ)) SLeaf SLeaf > z = SBranch (SS (SS SZ)) (SBranch SZ SLeaf SLeaf) SLeaf Seem to make sense ish. From: Nicholls, Mark Sent: 28 April 2015 9:33 AM To: Nicholls, Mark Subject: sds Hello, working through https://www.fpcomplete.com/user/konn/prove-your-haskell-for-great-safety/de… but a bit stuck...with an error... > {-# LANGUAGE DataKinds, TypeFamilies, TypeOperators, UndecidableInstances, GADTs, StandaloneDeriving #-} > data Nat = Z | S Nat > data Vector a n where > Nil :: Vector a Z > (:-) :: a -> Vector a n -> Vector a (S n) > infixr 5 :- I assume init...is a bit like tail but take n - 1 elements from the front....but... > init' :: Vector a ('S n) -> Vector a n > init' (x :- Nil) = Nil > init' (x :- xs@(_ :- _)) = x :- (init' xs) > zipWithSame :: (a -> b -> c) -> Vector a n -> Vector b n -> Vector c n > zipWithSame f Nil Nil = Nil > zipWithSame f (x :- xs) (y :- xs@(_ :- _)) = Nil Mark Nicholls | Senior Technical Director, Programmes & Development - Viacom International Media Networks A: 17-29 Hawley Crescent London NW1 8TT | e: Nicholls.Mark(a)vimn.com<mailto:mik@vimn.com> T: +44 (0)203 580 2223 [Description: cid:image001.png@01CD488D.9204D030] CONFIDENTIALITY NOTICE This e-mail (and any attached files) is confidential and protected by copyright (and other intellectual property rights). If you are not the intended recipient please e-mail the sender and then delete the email and any attached files immediately. Any further use or dissemination is prohibited. While MTV Networks Europe has taken steps to ensure that this email and any attachments are virus free, it is your responsibility to ensure that this message and any attachments are virus free and do not affect your systems / data. Communicating by email is not 100% secure and carries risks such as delay, data corruption, non-delivery, wrongful interception and unauthorised amendment. If you communicate with us by e-mail, you acknowledge and assume these risks, and you agree to take appropriate measures to minimise these risks when e-mailing us. MTV Networks International, MTV Networks UK & Ireland, Greenhouse, Nickelodeon Viacom Consumer Products, VBSi, Viacom Brand Solutions International, Be Viacom, Viacom International Media Networks and VIMN and Comedy Central are all trading names of MTV Networks Europe. MTV Networks Europe is a partnership between MTV Networks Europe Inc. and Viacom Networks Europe Inc. Address for service in Great Britain is 17-29 Hawley Crescent, London, NW1 8TT.

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CFP: IEEE International Conference on Cloud and Autonomic Computing (CAC 2015)
by Al-Nashif, Youssif B. 29 Apr '15

29 Apr '15

[ Less than two weeks to deadline. Apologies if you receive multiple copies of this email.] IEEE International Conference on Cloud and Autonomic Computing (CAC 2015) (pending IEEE support) autonomic-conference.org Cambridge, MA, USA September 21-25, 2015 Co-located with the Ninth IEEE International Conference on Self-Adaptive and Self-Organizing System (SASO 2015) and with the 15th IEEE Peer-to-Peer Computing Conference Call for Papers Overview Enterprise-scale cloud platforms and services systems, present common and cross-cutting challenges in maximizing power efficiency and performance while maintaining predictable and reliable behavior, and at the same time responding appropriately to environmental and system changes such as hardware failures and varying workloads. Autonomic computing systems address the challenges in managing these environments by integrating monitoring, decision-processing and actuation capabilities to autonomously manage resources and applications based on high-level policies. Research in cloud and autonomic computing spans a variety of areas, from computer systems, architecture, middleware services, databases and data-stores, and networks to machine learning and control theory. The purpose of the 3rd International Conference on Cloud and Autonomic Computing (CAC) is to bring together researchers and practitioners across these disciplines to address the multiple facets of self-management in computing systems and applications. Papers are solicited on a broad array of topics of relevance to cloud and autonomic computing and their intersections, particularly those that bear on connections and relationships among different research areas or report on prototype systems or experiences. The goal is to confirm a premier international forum focused on the latest research, applications, and technologies aimed at making cloud and autonomic computing systems and services easy to design, to deploy and to implement, while achieving the simultaneous goals to be self-manageable, self-regulating and scalable with little involvement of human or system administrators. Topics of interest include, but are not limited to: Autonomic Cloud Computing * Self-managing cloud services * Autonomic resource and energy management in cloud computing * Autonomic cloud applications and services * Autonomic virtual cloud resources and services * Cloud workload characterization and prediction * Monitoring, modeling and analysis of cloud resources and services * Anomaly behavior analysis of autonomic systems and services Autonomics for Extreme Scales * Large scale autonomic systems * Self-optimizing and self-healing at petacomputing scale * Self-managing middleware and tools for extreme scales * Experiences in autonomic systems and applications at extreme scales (peta/exa-computing) Autonomic Computing Foundations and Design Methods * Evaluation, validation and quality and correctness assessment of autonomic loops * Theoretical frameworks for modeling and analyzing autonomic computing systems, control and decision theory * Model-based design, software engineering, formal methods, testing, programming languages and environments support * Knowledge representation and visualization of behavior of autonomic systems and services Autonomic Computing Systems, Tools and Applications * Self-protection techniques of computing systems, networks and applications * Stochastic analysis and prediction of autonomic systems and applications * Benchmarks and tools to evaluate and compare different architectures to implement autonomic cloud systems * High performance autonomic applications * Self-* applications in science and engineering * Self-* Human Machine Interface Paper/Poster Submission and Publication: Full papers (a maximum of 12 pages in length), industrial experience reports (a maximum of 8 pages) and posters (a maximum of 4 pages) are invited on a wide variety of topics relating to cloud and autonomic computing as indicated above. All papers must follow the IEEE proceedings format. All manuscripts will be reviewed and judged on merits including originality, significance, interest, correctness, clarity, and relevance to the broader community. Papers are strongly encouraged to report experiences, measurements, and user studies, and to provide an appropriate quantitative evaluation. Submitted papers must include original work, and may not be under consideration for another conference or journal. They should also not be under review or be submitted to another forum during the CAC 2015 review process. Authors should submit full papers or posters electronically following the instructions from the CAC 2015 conference web site. Accepted papers and posters will appear in proceedings distributed at the conference and available electronically. Authors of accepted papers/poster are expected to present their work at the conference. Authors are also encouraged to submit a poster or demo that summarizes and highlights the main points of their paper. Workshops, Demonstrations and Exhibitions: CAC 2015 welcomes proposals for co-located workshops on specific topics of general interest to the cloud and autonomic computing community. Workshops are expected to publish proceedings, and should cover areas that may not be properly addressed in the main scientific program. CAC 2015 will also feature a demonstration and exhibition session consisting of prototypes and technology artifacts such as demonstrating autonomic software or autonomic computing principles. Important dates: * Abstract registration: May 8, 2015 * Papers submission deadline: May 15, 2015 * Authors notification: June 15, 2015 * Camera-ready papers due: July 1, 2015 Organizing Committee General Chair: * Danny Menasce (George Mason University, USA) PC Co-chairs: * Eric Rutten (INRIA, France) * Prashant Shenoy (University of Massachusetts Amherst, USA) PC Committee (preliminary list): * Karl-Erik Arzen, U. Lund, Sweden * Ioana Banicescu, Mississippi State Univ., USA * Thais Vasconcelos Batista, University of Rio Grande do Norte, Brazil * Umesh Bellur, IIT Bombay, India * Nelly Bencomo, Aston University, UK * Junwei Cao, Tsinghua University, China * Franck Cappello, Urbana-Champaign, USA * Giuliano Casale, Imperial College London, UK * Emiliano Casalicchio, University of Rome, Tor Vergata, Italy * Abhishek Chandra, University of Minnesota, USA * Lydia Y. Chen, IBM Research GmbH, Zurich, Switzerland * Fabio Costa, Universidade Federal de Goias, Brazil * Marco Danelutto, University of Pisa * Frederic Desprez, INRIA, France * Yixin Diao, IBM Research, USA * Jim Dowling, Swedish Institute of Computer Science (SICS), Sweden * Laurence Duchien, Universite de Lille/INRIA, France * Erik Elmroth, Umea University and Elastisys, Sweden * Antonio Filieri, University of Stuttgart, Germany * Harry Foxwell, Oracle, USA * Indranil Gupta, UIUC, USA * David Irwin, UMass, USA * Yoonhee Kim, Sookmyung Women's University, Korea * Hector Alejandro Duran Limon, Univ. de Guadalajara, Mexico * Martina Maggio, Lund University, Sweden * Maitreya Natu, TCS India * Marco D. Santambrogio, Politecnico di Milano, Italy * Tallat M. Shafaat, Google, Mountain View, CA, USA * Evgenia Smirni, College of William and Mary, VA, USA * Chris Stewart, Ohio State University, USA * Bhuvan Urgaonkar, Penn State Univ, USA * Timothy Wood, George Washington University, DC, USA * Dongyan Xu, Purdue University, USA Publicity Committee: * Youssif Al-Nashif, chair (Old Dominion University, USA) * Yaser Jararwah, co-chair (Jordan University of Science and Technology, Jordan) * Bharat Madan, co-chair (Old Dominion University, USA) * Ivan Rodero, co-chair (Rutgers University, USA) * Keiichi Shima, co-chair (Research Laboratory, IIJ Innovation Institute, Inc., Japan) * Jinsong Wu, co-chair (Universidad de Chile, Santiago, Chile) Steering Committee: * Simon Dobson (University of St Andrews, Scotland) * Geoffrey Fox (Indiana University Bloomington, USA) * Salim Hariri (University of Arizona, USA) * Soonwook Hwang (Korea Institute of Science and Technology Information, South Korea) * Julie McCann (Imperial College, UK) * Manish Parashar (Rutgers University, USA) * S. Masoud Sadjadi (Florida International University, USA) * Alan Sill (Texas Tech University, USA) * Vladimir Vlassov (KTH Royal Institute of Technology, Sweden)

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HTTP client library supporting Server sent events ?
by Alexandre Mazari 29 Apr '15

29 Apr '15

In an effort to build an Haskell client library for the Firebase service [0], which rely heavily on HTTP event source/server sent events [1], I am looking for an HTTP client lib supporting this spec. AFAIK, both WAI and yesod handle the mechanism server-side but nor http-client, wreq or http-streams seem to provide the client counterpart. Am I looking in the wrong direction? SSE are basically '\n' separated yaml messages over a kept open http response stream. I guess a seasoned Haskell dev could build a solution quite easily but o couldn't find a way to keep the response stream opened. Ideally a conduit/pipe sink exposing each message could be exposed for further parsing and usage. I'd be very glassful of someone could help me contribute such handling or come up with a solution. Thanks for your time, Alexandre [0] https://www.firebase.com/docs/rest/api/ [1] http://www.w3.org/TR/2011/WD-eventsource-20110208/ Le 29 avr. 2015 14:02, <haskell-cafe-request(a)haskell.org> a écrit : Send Haskell-Cafe mailing list submissions to haskell-cafe(a)haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe or, via email, send a message with subject or body 'help' to haskell-cafe-request(a)haskell.org You can reach the person managing the list at haskell-cafe-owner(a)haskell.org When replying, please edit your Subject line so it is more specific than "Re: Contents of Haskell-Cafe digest..." Today's Topics: 1. Re: Coplanarity or Colinearity [Was: low-cost matrix rank?] (Richard A. O'Keefe) 2. Re: Prime sieve and Haskell demo (Doug McIlroy) 3. Re: Prime sieve and Haskell demo (Kim-Ee Yeoh) 4. Wiki user (fr33domlover) 5. Re: Wiki user (Henk-Jan van Tuyl) 6. Re: Wiki user (fr33domlover) 7. Re: dependent types, singleton types.... (Richard Eisenberg) ---------------------------------------------------------------------- Message: 1 Date: Wed, 29 Apr 2015 13:14:36 +1200 From: "Richard A. O'Keefe" <ok(a)cs.otago.ac.nz> To: Mike Meyer <mwm(a)mired.org> Cc: Haskell-Cafe <Haskell-Cafe(a)haskell.org> Subject: Re: [Haskell-cafe] Coplanarity or Colinearity [Was: low-cost matrix rank?] Message-ID: <28B3FCD1-5BE8-4769-8BA9-A20D8426F4C2(a)cs.otago.ac.nz> Content-Type: text/plain; charset=us-ascii On 26/04/2015, at 1:53 am, Mike Meyer <mwm(a)mired.org> wrote: > My real problem is that I've got a list of points in R3 and want to decide if they determine a plane, meaning they are coplanar but not colinear. Similarly, given a list of points in R2, I want to verify that they aren't colinear. Both of these can be done by converting the list of points to a matrix and finding the rank of the matrix, but I only use the rank function in the definitions of colinear and coplanar. To compute the rank of a matrix, perform elementary row operations until the matrix is left in echelon form; the number of nonzero rows remaining in the reduced matrix is the rank. ( http://www.cliffsnotes.com/math/algebra/linear-algebra/real-euclidean-vecto… ) A matrix is in row echelon form when it satisfies the following conditions: * The first non-zero element in each row, called the leading entry, is 1 * Each leading entry is in a column to the right of the leading entry in the previous row * Rows with all zero elements, if any, are below rows having a non-zero element. (http://stattrek.com/matrix-algebra/echelon-transform.aspx) Row echelon forms aren't unique, but for determining the rank of a matrix, that doesn't matter. Code working on a list of points left as an exercise for the reader. ------------------------------ Message: 2 Date: Tue, 28 Apr 2015 21:36:52 -0400 From: Doug McIlroy <doug(a)cs.dartmouth.edu> To: haskell-cafe(a)haskell.org Subject: Re: [Haskell-cafe] Prime sieve and Haskell demo Message-ID: <201504290136.t3T1aqI1020799(a)coolidge.cs.dartmouth.edu> Content-Type: text/plain; charset=us-ascii With deep apologies for sending the wrong file, I try again. Doug >> How about simply changing `sieve` to `trialDiv`? It's not that I >> don't like the given example, because it gives a very small use case >> for laziness that is difficult enough to reproduce in an eagerly >> evaluated language. > > Is it really so difficult to reproduce in a strict language? Here is > that Haskell example in OCaml > > let primes = > let rec trialDiv (Cons (p,xs)) = > Cons (p, lazy (trialDiv @@ filter (fun x -> x mod p <> 0) @@ Lazy.force xs)) > in trialDiv @@ iota 2 I'm afraid I don't understand why the program isn't a sieve. Is the concern that the sequence of integers is thinned by dropping composites rather than by merely marking them and counting across them? Or is it that a trace of lazy evaluation will show that all the divisibility tests on a single integer are clustered together in time? Or something I haven't thought of? Of course the program can be written in any Turing-complete language, but the effort is likely to cause beads of sweat, like "lazy", "force", or "spawn" to be shed on the algorithmic pearl. The sieve can even be written succinctly as a bash shell script (below), which exhibits warts (e.g. five flavors of parentheses) but no sweat. Though both the Ocaml and the shell code are compact, neither dulls the luster that lazy evaluation imparts to the Haskell. sift() { while true; do read p if (( $p % $1 != 0 )); then echo $p; fi done } sink() { read p; echo $p; sift $p | sink } seq 2 1000000 | sink ------------------------------ Message: 3 Date: Wed, 29 Apr 2015 09:42:03 +0700 From: Kim-Ee Yeoh <ky3(a)atamo.com> To: Doug McIlroy <doug(a)cs.dartmouth.edu> Cc: Haskell Cafe <haskell-cafe(a)haskell.org> Subject: Re: [Haskell-cafe] Prime sieve and Haskell demo Message-ID: <CAPY%2BZdQsu4iotcjO7wRwqsLg34jnoQ7rhHWQ%3DrYwYBOVBnUj4g(a)mail.gmail.com> Content-Type: text/plain; charset="utf-8" On Wed, Apr 29, 2015 at 8:36 AM, Doug McIlroy <doug(a)cs.dartmouth.edu> wrote: > I'm afraid I don't understand why the program isn't a sieve. Is > the concern that the sequence of integers is thinned by dropping > composites rather than by merely marking them and counting across > them? Or is it that a trace of lazy evaluation will show that all > the divisibility tests on a single integer are clustered together > in time? Or something I haven't thought of? > When I reread Ertugrul's original email, I see that he's alerting to the danger of derision. There will be people who will mock Haskell for having an un-performant and un-Eratosthenian non-sieve on its front page. As in, Haskell people don't even know their basic math, ha ha. It used to be fibonaccis. That's too inviting of derision. Primes are more noble, so the thinking goes. That very small space on the face of Haskell must perform incredible duties. Among them, it has to showcase beautiful syntax, see: https://github.com/haskell-infra/hl/issues/46#issuecomment-72331664 HTH, -- Kim-Ee

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Re: [Haskell-cafe] Wiki user
by Henk-Jan van Tuyl 29 Apr '15

29 Apr '15

On Wed, 29 Apr 2015 08:07:36 +0200, fr33domlover <fr33domlover(a)riseup.net> wrote: > should send an e-mail. Could you please create a wiki account for me? The > username I'd like to have is: akrasner. Done. Regards, Henk-Jan van Tuyl -- Folding@home What if you could share your unused computer power to help find a cure? In just 5 minutes you can join the world's biggest networked computer and get us closer sooner. Watch the video. http://folding.stanford.edu/ http://Van.Tuyl.eu/ http://members.chello.nl/hjgtuyl/tourdemonad.html Haskell programming --

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Wiki user
by fr33domlover 29 Apr '15

29 Apr '15

Hello, The Haskell Wiki says automatic registration has been disabled, and that I should send an e-mail. Could you please create a wiki account for me? The username I'd like to have is: akrasner. Thanks in advance!

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