February 2017 - Haskell-Cafe

VSTTE 2017 - First Call for Papers
by Andrei Paskevich 17 Feb '17

17 Feb '17

9th Working Conference on Verified Software: Theories, Tools, and Experiments (VSTTE) https://vstte17.lri.fr July 22-23, 2017, Heidelberg, Germany Co-located with the 29th International Conference on Computer-Aided Verification, CAV 2017 Important Dates * Abstract submission: Mon, Apr 24, 2017 * Full paper submission: Mon, May 1, 2017 * Notification: Mon, Jun 5, 2017 * VSTTE: Sat-Sun, Jul 22-23, 2017 * Camera-ready: Mon, Aug 21, 2017 Overview The goal of the VSTTE conference series is to advance the state of the art in the science and technology of software verification, through the interaction of theory development, tool evolution, and experimental validation. We welcome submissions describing significant advances in the production of verified software, i.e., software that has been proved to meet its functional specifications. Submissions of theoretical, practical, and experimental contributions are equally encouraged, including those that focus on specific problems or problem domains. We are especially interested in submissions describing large-scale verification efforts that involve collaboration, theory unification, tool integration, and formalized domain knowledge. We also welcome papers describing novel experiments and case studies evaluating verification techniques and technologies. Topics of interest for VSTTE include education, requirements modeling, specification languages, specification/verification/certification case studies, formal calculi, software design methods, automatic code generation, refinement methodologies, compositional analysis, verification tools (e.g., static analysis, dynamic analysis, model checking, theorem proving, satisfiability), tool integration, benchmarks, challenge problems, and integrated verification environments. Paper Submissions We accept both long (limited to 16 pages) and short (limited to 10 pages) paper submissions. Short submissions also cover Verification Pearls describing an elegant proof or proof technique. Submitted research papers and system descriptions must be original and not submitted for publication elsewhere. Each submission will be evaluated by at least three members of the Program Committee. We expect that one author of every accepted paper will present their work at the conference. Paper submissions must be written in English using the LNCS LaTeX format (http://www.springer.com/gp/computer-science/lncs/conference-proceedings-gui…) and must include a cogent and self-contained description of the ideas, methods, results, and comparison to existing work. Papers will be submitted via EasyChair at the VSTTE 2017 conference page (https://www.easychair.org/conferences/?conf=vstte2017) The post-conference proceedings of VSTTE 2017 will be published in the LNCS series. Authors of accepted papers will be requested to sign the copyright transfer form. A selection of best papers will be invited for publication in the Journal of Automated Reasoning. Program Committee * June Andronick (University of New South Wales, Australia) * Christel Baier (TU Dresden, Germany) * Sandrine Blazy (Université de Rennes 1, France) * Arthur Charguéraud (Inria, France) * Ernie Cohen (Amazon Web Services, USA) * Rayna Dimitrova (MPI-SWS, Germany) * Carlo A. Furia (Chalmers University of Technology, Sweden) * Arie Gurfinkel (University of Waterloo, Canada) * Hossein Hojjat (Rochester Institute of Technology, USA) * Marieke Huisman (University of Twente, Netherlands) * Bart Jacobs (KU Leuven, Belgium) * Rajeev Joshi (NASA Jet Propulsion Laboratory, USA) * Zachary Kincaid (Princeton University, USA) * Akash Lal (Microsoft Research, India) * Shuvendu Lahiri (Microsoft Research, USA) * Francesco Logozzo (Facebook, USA) * Peter Müller (ETH Zürich, Switzerland) * Jorge A. Navas (SRI International, USA) * Scott Owens (University of Kent, UK) * Andrei Paskevich (Université Paris-Sud, France), co-chair * Gerhard Schellhorn (Universität Augsburg, Germany) * Peter Schrammel (University of Sussex, UK) * Natarajan Shankar (SRI International, USA) * Mihaela Sighireanu (Université Paris-Diderot, France) * Julien Signoles (CEA LIST, France) * Michael Tautschnig (Queen Mary University of London, UK) * Tachio Terauchi (JAIST, Japan) * Oksana Tkachuk (NASA Ames Research Center, USA) * Mattias Ulbrich (Karlsruhe Institute of Technology, Germany) * Thomas Wies (New York University, USA), co-chair

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How to code Haskell in KDevelop in Windows
by vinod kc 16 Feb '17

16 Feb '17

Hi, I am new in Haskell. I installed GHC and KDevelop. But i don't know how to setup Haskell in KDevelop. Can anybody help me ? Thanks in advance -Vinod

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Self updating binary
by Pieter Laeremans 16 Feb '17

16 Feb '17

Hi there, Has anyone experience suggestions with writing self updating binaries for windows ? I have a small utility that I have to install on two "unmanaged" pc's, I would like to let the program check an url, for new versions, download a new versions, some how check that the program is valid (with a build in key, or certificate) and replace itself when necessary. Has anyone already done this in Haskell? Any suggestions, links ? Thanks, Pieter -- Pieter Laeremans pieter(a)laeremans.org

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Final Call for Papers: ICFP 2017
by Lindsey Kuper 15 Feb '17

15 Feb '17

ICFP 2017 The 22nd ACM SIGPLAN International Conference on Functional Programming Oxford, United Kingdom http://icfp17.sigplan.org/ Final Call for Papers ### Important dates Submissions due: Monday, February 27, Anywhere on Earth https://icfp17.hotcrp.com Author response: Monday, April 17, 2017, 15:00 (UTC) - Thursday, April 20, 2017, 15:00 (UTC) Notification: Monday, 1 May, 2017 Final copy due: Monday, 5 June 2017 Early registration: TBA Conference: Monday, 4 September - Wednesday, 6 September, 2017 ### New this year Those familiar with previous ICFP conferences should be aware of two significant changes that are being introduced in 2017: 1. Papers selected for ICFP 2017 will be published as the ICFP 2017 issue of a new journal, Proceedings of the ACM on Programming Languages (PACMPL), which replaces the previous ICFP conference proceedings. The move to PACMPL will have two noticeable impacts on authors: * A new, two-phase selection and reviewing process that conforms to ACM’s journal reviewing guidelines. * A new, single-column format for submissions. 2. Authors of papers that are conditionally accepted in the first phase of the reviewing process will have the option to submit materials for Artifact Evaluation. Further details on each of these changes are included in the following text. ### Scope ICFP 2017 seeks original papers on the art and science of functional programming. Submissions are invited on all topics from principles to practice, from foundations to features, and from abstraction to application. The scope includes all languages that encourage functional programming, including both purely applicative and imperative languages, as well as languages with objects, concurrency, or parallelism. Topics of interest include (but are not limited to): * *Language Design*: concurrency, parallelism, and distribution; modules; components and composition; metaprogramming; type systems; interoperability; domain-specific languages; and relations to imperative, object-oriented, or logic programming. * *Implementation*: abstract machines; virtual machines; interpretation; compilation; compile-time and run-time optimization; garbage collection and memory management; multi-threading; exploiting parallel hardware; interfaces to foreign functions, services, components, or low-level machine resources. * *Software-Development Techniques*: algorithms and data structures; design patterns; specification; verification; validation; proof assistants; debugging; testing; tracing; profiling. * *Foundations*: formal semantics; lambda calculus; rewriting; type theory; monads; continuations; control; state; effects; program verification; dependent types. * *Analysis and Transformation*: control-flow; data-flow; abstract interpretation; partial evaluation; program calculation. * *Applications*: symbolic computing; formal-methods tools; artificial intelligence; systems programming; distributed-systems and web programming; hardware design; databases; XML processing; scientific and numerical computing; graphical user interfaces; multimedia and 3D graphics programming; scripting; system administration; security. * *Education*: teaching introductory programming; parallel programming; mathematical proof; algebra. Submissions will be evaluated according to their relevance, correctness, significance, originality, and clarity. Each submission should explain its contributions in both general and technical terms, clearly identifying what has been accomplished, explaining why it is significant, and comparing it with previous work. The technical content should be accessible to a broad audience. ICFP 2017 also welcomes submissions in two separate categories --- Functional Pearls and Experience Reports --- that must be marked as such at the time of submission and that need not report original research results. Detailed guidelines on both categories are given at the end of this call. Please contact the program chair if you have questions or are concerned about the appropriateness of a topic. ### Preparation of submissions ICFP 2017 will employ a lightweight double-blind reviewing process, as described below. **Deadline**: The deadline for submissions is Monday, February 27, 2017, Anywhere on Earth (<https://en.wikipedia.org/wiki/Anywhere_on_Earth>). This deadline will be strictly enforced. **Formatting**: (NOTE: NEW FORMAT REQUIREMENTS FOR ICFP 2017) Submissions must be in PDF format, printable in black and white on US Letter sized paper, and interpretable by common PDF tools. All submissions must adhere to the "ACM Large" template that is available (in both LaTeX and Word formats) from <http://www.acm.org/publications/proceedings-template>. For authors using LaTeX, a lighter-weight package, including only the essential files, is available from <http://sigplan.org/Resources/Author/#acmart-format>; the appropriate template for ICFP 2017 authors is in the file `acmart-pacmpl-template.tex`. As documented in the template, submissions should be prepared using the `acmlarge` and `anonymous` options. The use of the `review` option is also strongly encouraged but not required. (The `review` option will add line numbers, which will make it easier for reviewers to reference specific parts of your paper in their comments, but should have absolutely no other effect on the typesetting.) Details of available technical support for LaTeX-specific questions is available at <http://www.acm.org/publications/proceedings-template#h-technical-support>. There is a limit of 24 pages for a full paper or 12 pages for an Experience Report; in either case, the bibliography will not be counted against these limits. These page limits have been chosen to allow essentially the same amount of content with the new single-column format as was possible with the two-column format used in past ICFP conferences. Submissions that exceed the page limits or, for other reasons, do not meet the requirements for formatting, will be summarily rejected. **Citations**: As part of PACMPL, ICFP 2017 papers are expected to use author-year citations for references to other work. Author-year citations may be used as either a noun phrase, such as "The lambda calculus was originally conceived by Church (1932)", or a parenthetic phrase, such as "The lambda calculus (Church 1932) was intended as a foundation for mathematics". A useful test for correct usage it to make sure that the text still reads correctly when the parenthesized portions of any references are omitted. Take care with prepositions; in the first example above, "by" is more appropriate than "in" because it allows the text to be read correctly as a reference to the author. Sometimes, readability may be improved by putting parenthetic citations at the end of a clause or a sentence, such as "A foundation for mathematics was provided by the lambda calculus (Church 1932)". In LaTeX, use `\citet{Church-1932}` for citations as a noun phrase, "Church (1932)", and `\citep{Church-1932}` for citations as a parenthetic phrase, "(Church 1932)"; for details, see Sections 2.3--2.5 of the natbib documentation (<http://ctan.org/pkg/natbib>). **Submission**: Submissions will be accepted at <https://icfp17.hotcrp.com/>. Improved versions of a paper may be submitted at any point before the submission deadline using the same web interface. **Author Response Period**: Authors will have a 72-hour period, starting at 15:00 UTC on Monday, April 17, 2017, to read reviews and respond to them. **Supplementary Materials**: Authors have the option to attach supplementary material to a submission, on the understanding that reviewers may choose not to look at it. The material should be uploaded at submission time, as a single pdf or a tarball, not via a URL. This supplementary material may or may not be anonymized; if not anonymized, it will only be revealed to reviewers after they have submitted their review of the paper and learned the identity of the author(s). **Authorship Policies**: All submissions are expected to comply with the ACM Policies for Authorship that are detailed at <https://www.acm.org/publications/authors/information-for-authors>. **Republication Policies**: Each submission must adhere to SIGPLAN's republication policy, as explained on the web at <http://www.sigplan.org/Resources/Policies/Republication>. **Resubmitted Papers**: Authors who submit a revised version of a paper that has previously been rejected by another conference have the option to attach an annotated copy of the reviews of their previous submission(s), explaining how they have addressed these previous reviews in the present submission. If a reviewer identifies him/herself as a reviewer of this previous submission and wishes to see how his/her comments have been addressed, the program chair will communicate to this reviewer the annotated copy of his/her previous review. Otherwise, no reviewer will read the annotated copies of the previous reviews. ### Review Process This section outlines the two-stage process with lightweight double-blind reviewing that will be used to select papers for presentation at ICFP 2017. A [list of frequently asked questions and answers](http://icfp17.sigplan.org/track/icfp-2017-papers#Submission-and-Re… that address common concerns is available on the conference website and will be updated as necessary to clarify and expand on this process. **ICFP 2017 will employ a two-stage review process.** The first stage in the review process will assess submitted papers using the criteria stated above and will allow for feedback and input on initial reviews through the author response period mentioned previously. At the PC meeting, a set of papers will be conditionally accepted and all other papers will be rejected. Authors will be notified of these decisions on May 1, 2017. Authors of conditionally accepted papers will be provided with committee reviews (just as in previous conferences) along with a set of mandatory revisions. After five weeks (June 5, 2017), the authors will provide a second submission. The second and final reviewing phase assesses whether the mandatory revisions have been adequately addressed by the authors and thereby determines the final accept/reject status of the paper. The intent and expectation is that the mandatory revisions can be addressed within five weeks and hence that conditionally accepted papers will in general be accepted in the second phase. The second submission should clearly identify how the mandatory revisions were addressed. To that end, the second submission must be accompanied by a cover letter mapping each mandatory revision request to specific parts of the paper. The cover letter will facilitate a quick second review, allowing for confirmation of final acceptance within two weeks. Conversely, the absence of a cover letter will be grounds for the paper’s rejection. This process is intended as a refinement of the review process that has been used in previous ICFP conferences. By incorporating a second stage, the process will conform to ACM’s journal reviewing guidelines for PACMPL. **ICFP 2017 will employ a lightweight double-blind reviewing process.** To facilitate this, submitted papers must adhere to two rules: 1. **author names and institutions must be omitted**, and 2. **references to authors' own related work should be in the third person** (e.g., not "We build on our previous work ..." but rather "We build on the work of ..."). The purpose of this process is to help the PC and external reviewers come to an initial judgement about the paper without bias, not to make it impossible for them to discover the authors if they were to try. Nothing should be done in the name of anonymity that weakens the submission or makes the job of reviewing the paper more difficult (e.g., important background references should not be omitted or anonymized). In addition, authors should feel free to disseminate their ideas or draft versions of their paper as they normally would. For instance, authors may post drafts of their papers on the web or give talks on their research ideas. ### Information for Authors of Accepted Papers * As a condition of acceptance, final versions of all papers must adhere to the new ACM Large format. The page limits for final versions of papers will be increased to ensure that authors have space to respond to reviewer comments and mandatory revisions. * Authors of accepted submissions will be required to agree to one of the three ACM licensing options: copyright transfer to ACM; retaining copyright but granting ACM exclusive publication rights; or open access on payment of a fee. Further information about ACM author rights is available from <http://authors.acm.org>. * At least one author of each accepted submission will be expected to attend and present their paper at the conference. (ICFP welcomes all authors, regardless of nationality. If any author of an accepted submission has visa-related difficulties in travelling to the conference, we will make arrangements to enable remote participation, and not require them to attend the conference in order to present their talk. In such a case contact us (icfp2017(a)cs.ox.ac.uk) for further guidance.) The schedule for presentations will be determined and shared with authors after the full program has been selected. Presentations will be videotaped and released online if the presenter consents. * We intend that the proceedings will be freely available for download from the ACM Digital Library in perpetuity via the OpenTOC mechanism. * ACM Author-Izer is a unique service that enables ACM authors to generate and post links on either their home page or institutional repository for visitors to download the definitive version of their articles from the ACM Digital Library at no charge. Downloads through Author-Izer links are captured in official ACM statistics, improving the accuracy of usage and impact measurements. Consistently linking to the definitive version of an ACM article should reduce user confusion over article versioning. After an article has been published and assigned to the appropriate ACM Author Profile pages, authors should visit <http://www.acm.org/publications/acm-author-izer-service> to learn how to create links for free downloads from the ACM DL. * **AUTHORS TAKE NOTE: The official publication date is the date the proceedings are made available in the ACM Digital Library. This date may be up to *two weeks prior* to the first day of the conference. The official publication date affects the deadline for any patent filings related to published work.** ### Artifact Evaluation Authors of papers that are conditionally accepted in the first phase of the review process will be encouraged (but not required) to submit supporting materials for Artifact Evaluation. These items will then be reviewed by a committee, separate from the program committee, whose task is to assess how the artifacts support the work described in the associated paper. Papers that go through the Artifact Evaluation process successfully will receive a seal of approval printed on the papers themselves. Authors of accepted papers will be encouraged to make the supporting materials publicly available upon publication of the proceedings, for example, by including them as "source materials" in the ACM Digital Library. An additional seal will mark papers whose artifacts are made available, as outlined in the ACM guidelines for artifact badging. Participation in Artifact Evaluation is voluntary and will not influence the final decision regarding paper acceptance. Further information about the motivations and expectations for Artifact Evaluation can be found at <http://icfp17.sigplan.org/track/icfp-2017-Artifacts>. ### Special categories of papers In addition to research papers, ICFP solicits two kinds of papers that do not require original research contributions: Functional Pearls, which are full papers, and Experience Reports, which are limited to half the length of a full paper. Authors submitting such papers should consider the following guidelines. #### Functional Pearls A Functional Pearl is an elegant essay about something related to functional programming. Examples include, but are not limited to: * a new and thought-provoking way of looking at an old idea * an instructive example of program calculation or proof * a nifty presentation of an old or new data structure * an interesting application of functional programming techniques * a novel use or exposition of functional programming in the classroom While pearls often demonstrate an idea through the development of a short program, there is no requirement or expectation that they do so. Thus, they encompass the notions of theoretical and educational pearls. Functional Pearls are valued as highly and judged as rigorously as ordinary papers, but using somewhat different criteria. In particular, a pearl is not required to report original research, but, it should be concise, instructive, and entertaining. A pearl is likely to be rejected if its readers get bored, if the material gets too complicated, if too much specialized knowledge is needed, or if the writing is inelegant. The key to writing a good pearl is polishing. A submission that is intended to be treated as a pearl must be marked as such on the submission web page, and should contain the words "Functional Pearl" somewhere in its title or subtitle. These steps will alert reviewers to use the appropriate evaluation criteria. Pearls will be combined with ordinary papers, however, for the purpose of computing the conference's acceptance rate. #### Experience Reports The purpose of an Experience Report is to help create a body of published, refereed, citable evidence that functional programming really works --- or to describe what obstacles prevent it from working. Possible topics for an Experience Report include, but are not limited to: * insights gained from real-world projects using functional programming * comparison of functional programming with conventional programming in the context of an industrial project or a university curriculum * project-management, business, or legal issues encountered when using functional programming in a real-world project * curricular issues encountered when using functional programming in education * real-world constraints that created special challenges for an implementation of a functional language or for functional programming in general An Experience Report is distinguished from a normal ICFP paper by its title, by its length, and by the criteria used to evaluate it. * Both in the proceedings and in any citations, the title of each accepted Experience Report must begin with the words "Experience Report" followed by a colon. The acceptance rate for Experience Reports will be computed and reported separately from the rate for ordinary papers. * Experience Report submissions can be at most 12 pages long, excluding bibliography. * Each accepted Experience Report will be presented at the conference, but depending on the number of Experience Reports and regular papers accepted, authors of Experience reports may be asked to give shorter talks. * Because the purpose of Experience Reports is to enable our community to accumulate a body of evidence about the efficacy of functional programming, an acceptable Experience Report need not add to the body of knowledge of the functional-programming community by presenting novel results or conclusions. It is sufficient if the Report states a clear thesis and provides supporting evidence. The thesis must be relevant to ICFP, but it need not be novel. The program committee will accept or reject Experience Reports based on whether they judge the evidence to be convincing. Anecdotal evidence will be acceptable provided it is well argued and the author explains what efforts were made to gather as much evidence as possible. Typically, more convincing evidence is obtained from papers which show how functional programming was used than from papers which only say that functional programming was used. The most convincing evidence often includes comparisons of situations before and after the introduction or discontinuation of functional programming. Evidence drawn from a single person's experience may be sufficient, but more weight will be given to evidence drawn from the experience of groups of people. An Experience Report should be short and to the point: it should make a claim about how well functional programming worked on a particular project and why, and produce evidence to substantiate this claim. If functional programming worked in this case in the same ways it has worked for others, the paper need only summarize the results --- the main part of the paper should discuss how well it worked and in what context. Most readers will not want to know all the details of the project and its implementation, but the paper should characterize the project and its context well enough so that readers can judge to what degree this experience is relevant to their own projects. The paper should take care to highlight any unusual aspects of the project. Specifics about the project are more valuable than generalities about functional programming; for example, it is more valuable to say that the team delivered its software a month ahead of schedule than it is to say that functional programming made the team more productive. If the paper not only describes experience but also presents new technical results, or if the experience refutes cherished beliefs of the functional-programming community, it may be better off submitted it as a full paper, which will be judged by the usual criteria of novelty, originality, and relevance. The program chair will be happy to advise on any concerns about which category to submit to. ### Organizers General Chair: Jeremy Gibbons (University of Oxford, UK) Program Chair: Mark Jones (Portland State University, USA) Artifact Evaluation Chair: Ryan R. Newton (Indiana University, USA) Industrial Relations Chair: Ryan Trinkle (Obsidian Systems LLC, USA) Programming Contest Organiser: Sam Lindley (University of Edinburgh, UK) Publicity and Web Chair: Lindsey Kuper (Intel Labs, USA) Student Research Competition Chair: Ilya Sergey (University College London, UK) Video Chair: Jose Calderon (Galois, Inc., USA) Workshops Co-Chair: Andres Löh (Well-Typed LLP) Workshops Co-Chair: David Christiansen (Indiana University, USA) Program Committee: Bob Atkey (University of Strathclyde, Scotland) Adam Chlipala (MIT, USA) Dominique Devriese (KU Leuven, Belgium) Martin Erwig (Oregon State, USA) Matthew Flatt (University of Utah, USA) Ronald Garcia (University of British Columbia, Canada) Kathryn Gray (University of Cambridge, England) John Hughes (Chalmers University and Quvik, Sweden) Chung-Kil Hur (Seoul National University, Korea) Graham Hutton (University of Nottingham, England) Alan Jeffrey (Mozilla Research, USA) Ranjit Jhala (University of California, San Diego, USA) Shin-ya Katsumata (Kyoto University, Japan) Lindsey Kuper (Intel Labs, USA) Dan Licata (Wesleyan University, USA) Ben Lippmeier (Digital Asset, Australia) Gabriel Scherer (Northeastern University, USA) Alexandra Silva (University College London, England) Nikhil Swamy (Microsoft Research, USA) Sam Tobin-Hochstadt (Indiana University, USA) Nicolas Wu (University of Bristol, England) Beta Ziliani (CONICET and FAMAF, Universidad Nacional de Córdoba, Argentina)

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Re: [Haskell-cafe] Extensible records & mandatory/optional record fields
by Anthony Clayden 15 Feb '17

15 Feb '17

> On 15 February 2017 at 23:06 Harendra Kumar wrote: >> On 16 February 2017 at 02:31, Anthony Clayden wrote: > > > I am aware of the ghc "overloaded records" proposal. rawr > provides anonymous extensible records using the overloaded > labels feature of ghc 8. Records can be merged or > partitioned. I believe, the key difference between > "overloaded records" and rawr is that the latter provides > extensible records while the former does not. Yes. But you seem to be talking about a different 'feature' of rawr. For gathering params to a function, I see no need for extensible records. The params are known at compile time. If for a DSL you want 'optional' fields, make them Maybe's, with a default of Nothing. > > I am trying to write a program which provides a friendly > high level DSL to the user. 'user' here seems to mean programmer, if you're looking for static guarantees. > I want a pure function like > API but instead of passing positional parameters I want > the user to be able to specify arguments based on keywords > and be able to skip any optional arguments. Something like > the following, name is mandatory and email is optional: > > maintainer (#name := "Harendra Kumar", #email := > "xyz(a)gmail.com") > > I can achieve this using rawr. The argument to the > function is an anonymous record ... OK. But I'm not seeing why it has to be anonymous. Again, if it's for a specific function, it needs specific parameters. An anonymous record might provide keywords not valid, as well as fail to provide keywords expected. > and we can pattern match > partially using the mandatory fields in the record to > statically check that those fields are present. OK. That's the critical feature you want, then. It wasn't clear from your O.P. > > I was only trying to say that this is a pretty > useful feature in python and I guess in some other > imperative languages too. (I don't think it's anything to do with programming paradigm.) > It allows you to write self > documenting code where necessary. No the code you posted was not self-documenting. (The comments were useful, thank you.) Only a python-charmer would claim code full of graphic chars is 'self-documenting'. I have no idea what it was that made #name mandatory but #email not. > It will be nice if we have a way to achieve something like this. > There's nothing in the standard language currently. > > [example] > This is the first approach that I tried, this is commonly > used in many libraries. The only drawback with this is > that I cannot enforce mandatory/optional fields > statically. All fields are optional in this case. So your DSL is going to be compiled? Not intepreted? Including putting in values like #name? I'd expect #name would come from end-user input at run time(?) Yes the approach I illustrated is common in many libraries. Perhaps authors of those libraries are listening in, and could comment. AntC

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Re: [Haskell-cafe] Extensible records & mandatory/optional record fields
by Anthony Clayden 15 Feb '17

15 Feb '17

> On Tue, 14 Feb 2017 at 18:50, Harendra Kumar said: > In my application, I want some of the fields in a record to have default > values while others must always be specified by the user. I can implement > this using the rawr records library (http://hackage.haskell.org/package/rawr) Hi Harendra. I believe rawr builds on some of the work in 'overloaded records'. That's a suite of features being developed right now look here for what's coming soon https://github.com/adamgundry/ghc-proposals/blob/overloaded-record-fields/p… > like so: > > def :: ("b" := String) -> R ("a" := Int, "b" := String) > def t = (R (#a := 0) :*: R t) -- merge with defaults > > let r = def (#b := "hello") That looks like some sort of anonymous/extensible records system. What is data constructor `R`; where is it defined? There's a few mentions of 'anonymous' records on that link above. (And mention of rawr.) It's not clear what you're trying to do. Do you need anonymous/extensible records? Why use `let` to bind a value for `r`? > Here field "a" has a default value (i.e. it is optional when "def" is used) > but field "b" does not have a default value and has to be explicitly > specified by the user. This is made possible by record merging feature of > rawr, making the record extensible. > I could not find an equivalent way of achieving this using overloaded > records (http://hackage.haskell.org/package/overloaded-records) So far, overloaded records is based on standard-ish Haskell record decls. So you must declare a distinct record constructor and field labels. Like data MyR = MyR { a :: Int, b :: String }; If you want default values: myRdef = MyR{ a = 0 }; -- don't have to give b Then bind some value, to incorp defaults. r = myRdef { b = "hello" }; -- takes the defult for a > Is record merging possible or can be made possible It looks to me like you don't need '"record merging". What do you think it is; why do you think you need it? > using overloaded-records or with the ghc overloaded records poposal? > If not, is there a plan to make something like this possible in future? I'd say it's on the radar, but a long way off. > Or will this never be possible with the in built record syntax? I think that built-in record syntax will fit your requirements. > Note that, this is handy to simulate mandatory and optional keyword > arguments to a function by passing them in the form of a record. Sure. Keyword arguments to a function are fixed. No need for building dynamic/anonymous structures. Yes it's good (and standard practice) to pass as a record. So you can use a standard built-in Haskell record decl, as I used above. > Something which is available in other languages like python. It looks to me that you're trying to write Python code in Haskell. Not a good idea. Use built-in/static features first. Think about the difference between a compiled vs interpreted language. Only when static features really really aren't working, consider dynamic/extensible. AntC

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Applicative transformers
by Laurent Christophe 15 Feb '17

15 Feb '17

Hi guys, the way `StateT` are implemented as `Applicative` have been buggling my mind for some time. https://hackage.haskell.org/package/transformers-0.5.2.0/docs/src/Control.M… <https://hackage.haskell.org/package/transformers-0.5.2.0/docs/src/Control.M…> instance (Functor m, Monad m) => Applicative (StateT s m) where pure a = StateT $ \ s -> return (a, s) StateT mf <*> StateT mx = StateT $ \ s -> do (f, s') <- mf s (x, s'') <- mx s' return (f x, s'') Using dependant monadic computations, this implementation cannot be expressed in term of applicative. This explains why we cannot have `instance (Applicative m) => Applicative (State s m)`. However using real monadic style computations for implementing `<*>` buggles my mind. Moreover `liftA2 (<*>)` can be used to generically compose applicative functors so why monads are needed? https://www.haskell.org/haskellwiki/Applicative_functor#Applicative_transfo… <https://www.haskell.org/haskellwiki/Applicative_functor#Applicative_transfo…> Any inputs would be greatly appreciated! Cheers, Laurent

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1st call for papers: Trends in Functional Programming, 19-21 june 2017, University of Kent, Canterbury
by Peter Achten 15 Feb '17

15 Feb '17

----------------------------- C A L L F O R P A P E R S ----------------------------- ======== TFP 2017 =========== 18th Symposium on Trends in Functional Programming 19-21 June, 2017 University of Kent, Canterbury https://www.cs.kent.ac.uk/events/tfp17/index.html 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. TFP 2017 will be the main event of a pair of functional programming events. TFP 2017 will be accompanied by the International Workshop on Trends in Functional Programming in Education (TFPIE), which will take place on 22 June. 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; * Soesterberg (The Netherlands) in 2014; * Inria Sophia-Antipolis (France) in 2015; * and Maryland (USA) in 2016. For further general information about TFP please see the TFP homepage. (http://www.tifp.org/) == 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, but are not limited to: 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 2017 program chairs, Scott Owens and Meng Wang. == 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 == TBD == PAPER SUBMISSIONS == Acceptance of articles for presentation at the symposium is based on a lightweight peer review process of extended abstracts (4 to 10 pages in length) or full papers (20 pages). The submission must clearly indicate which category it belongs to: research, position, project, evaluation, or overview paper. It should also indicate which authors are research students, and whether the main author(s) are students. A draft paper for which ALL authors are students will receive additional feedback by one of the PC members shortly after the symposium has taken place. We use EasyChair for the refereeing process. Papers must be submitted at: https://easychair.org/conferences/?conf=tfp17 Papers must be written in English, and written using the LNCS style. For more information about formatting please consult the Springer LNCS web site: http://www.springer.com/computer/lncs?SGWID=0-164-6-793341-0 == IMPORTANT DATES == Submission of draft papers: 5 May, 2017 Notification: 12 May, 2017 Registration: 11 June, 2017 TFP Symposium: 19-21 June, 2017 Student papers feedback: 29 June, 2017 Submission for formal review: 2 August, 2017 Notification of acceptance: 3 November, 2017 Camera ready paper: 2 December, 2017 == PROGRAM COMMITTEE == TBD

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Re: [Haskell-cafe] Lenses and records and ecosystem
by Anthony Clayden 14 Feb '17

14 Feb '17

> On Sat, Feb 11, 2017 at 21:04, David Menendez wrote: > > On Fri, Feb 10, 2017 at 7:53 PM, Anthony Clayden wrote: > > > > Certainly (.) for lenses works 'backwards' > > (i.e. suffix style) > > compared to function-prefix style. > > (As any Lens tutorial will say.) > > > > Those tutorials are oversimplifying. Thank you David, ho hum I'm not getting much feedback about ecosystem/ co-existence; nor a specialised composition operator. > Lenses (and their relatives) transform operations, not values. So it must be a stubborn superstition on my part that getting/putting from/to structures is about values. I'm not here to 'knock' lenses (of whichever model), but every time I scratch the surface, the answers wander off into category theory and higher-order types. I'll draw a comparison with another place in Haskell where category theory has huge benefits: monads. There's less than a handful of operators for monads, and those are conveniently handled behind some elegant syntactic sugar (do-notation). So a newbie doesn't really need to grok monads. They can get on and use them; learn the theory later. Can that be said of lenses? I guess part of the trouble is that H98 record operations have gobbled up so much of the syntactic design space. Nevertheless I don't see what syntactic sugar could help with lenses. > Composition of lenses is exactly like composition of functions, with > the inner-most operation on the right. That doesn't seem to say more than "it's composition". If I want to get a foo out of a bar out of a baz in a s, I'd (perhaps naievely) go foo (bar (baz s)) -- i.e. (foo . bar . baz) s And I'm using function application all the way through. I'd only think of doing s.baz.bar.foo If I was trying to mimic OO style methods. And anyway with lenses, that's exactly what I _can't_ do. Lenses do not use function application of the lens to the structure. You need an extra operator (view, over). Then I'm not seeing the syntactic merit of using composition (.) for lenses. It's certainly making the mental machinery incompatible for lenses vs records, even if they can co-exist semantically. > A lens foo :: Lens > O I transforms an operation on I into an operation on O. A > composition outer.inner turns an operation on the target > of inner into an operation on the source of outer. > > This is demonstrated by the way over distributes with (.): > > over (outer . inner) = over outer . over inner > > What confuses people is view, which is contravariant: > > view (outer . inner) = view inner . view outer > > but you can't avoid having one of over and view be > contravariant. OK. (Why did it need so much category theory to explain that?) And why do those nifty equivalences have to intrude so much into the surface syntax, just to get a value out of a structure? AntC

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Haskell.org committee financial statement 2016
by Gershom B 14 Feb '17

14 Feb '17

Dear Haskellers, The Haskell.org Committee [1] manages funds for haskell.org and oversees haskell.org infrastructure. The funds available to Haskell.org have historically come from two sources: 1) Mentor payments from the Google Summer of Code program. 2) Donations [2] from the Haskell community at large. Haskell.org is a registered 501(c)3 nonprofit. A portion of our funds are held by Software in the Public Interest, also a 501(c)3 US non-profit, through which we also accept donations. In 2016 we were not accepted into the GSoC program, and ran a summer of haskell program along similar lines, funded by earmarked donations provided by individual and corporate sponsors and from our pool of general funds. A full list of sponsors is on the soh webpage [3]. According to our charter, "Each year, the committee will post a statement of the haskell.org assets, and the transactions for that year." Included in this message is a brief statement of Haskell.org assets over the period 1 December 2015 - 31 December 2016. Aside from the SOH disbursements, our expenses are nearly entirely hosting, with a small overhead incurred by payment processing. SOH thus accounts for both our increased revenue (in the form of earmarked donations) and expenses this year. We do not have full statements from our SPI account yet, as their treasury reports are only complete through october at this time [4] although I hope that will be changed shortly. So this statement is produced as though the income and expenses on our spi account for the last for months of 2016 were net zero, though that was obviously not the case. Even in this incomplete state, I think it is better to provide this than nothing. Additionally, as this covers holdings in our haskell.org bank account, it does not reflect when funds received via paypal donations, are received by paypal, but rather when the lump sum transfers from them are received by us. So paypal donations made in December 2016, for example, will likely be reflected in our 2017 statement. A portion of the income in 2016 is also attributable to gsoc mentor payment from our participation in the 2015 program. Thanks to many generous donations, despite the substantial haskell summer of code expenditures, we are nonetheless net-positive in income (though the difference just about amounts to the outstanding gsoc payments from 2015). We hope to find good opportunity to put our reserves to use again in the coming year. 1. Income and Expenses Total revenue over 2016: 54,802.56 Total expenses over 2016: 48,344.05 ---- Net income over 2016: 6,458.51 2. Total Balance Balance as of 31 December 2015: 32,882.34 Balance as of 31 December 2016: 39,340.85 [1] https://wiki.haskell.org/Haskell.org_committee [2] https://wiki.haskell.org/Donate_to_Haskell.org [3] https://summer.haskell.org/ [5] http://spi-inc.org/treasurer/reports/ Best, Gershom for the Haskell.org Committee

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