- Haskell-Cafe - Haskell.org

Trouble building happy/alex with Stack lts-9.20
by Eric McCorkle 25 Dec '17

25 Dec '17

Hi folks, I'm trying to update my language project to happy >= 9.16, so I can use typeclass-based parsers. Unfortunately, I'm running into build errors after switching to lts-9.20. The log file is attached. I see similar problems when trying to build alex (the lexer generator). It seems to be claiming that there is no cabal file, which is odd, as there clearly is one (in the source at least). Has anyone else seen this problem, and if so, what is the workaround?

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Supporting Haskell.org
by Tikhon Jelvis 25 Dec '17

25 Dec '17

A significant part of the Haskell community infrastructure—including the haskell.org website, Hackage, Hoogle and the build infrastructure for GHC—runs on donations from the Haskell community administered by haskell.org . You can donate right now using several methods including PayPal and check: https://wiki.haskell.org/Donate_to_Haskell.org Haskell.org can also accept donations through employers via Benevity using the unique ID 475236502. As Haskell.org is a 501(c)(3) non-profit, donations are tax-deductible. This year marked the second Haskell Summer of Code program which provided grants for 15 students working on open source Haskell projects over the summer. The projects improved Haskell tooling and libraries as well as supporting Haskell education through improvements to code.world. A detailed retrospective can be found on summer.haskell.org: https://summer.haskell.org/news/2017-09-15-final-results.html With look forward to continuing this work with your support in 2018 as well as exploring new projects to improve the Haskell community infrastructure. Best wishes, Tikhon Jelvis on behalf of the haskell.org committee.

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ANN: progress-meter 1.0.0
by esz＠posteo.de 25 Dec '17

25 Dec '17

Hi everybody, I have just released a complete API rewrite of the `progress-meter` package: * <https://hackage.haskell.org/package/progress-meter> * <https://github.com/esoeylemez/progress-meter> With this package you can easily add live diagnostics to any long-running application from a simple progress bar to full task monitoring. The `System.Progress` module contains a tutorial. Features: * update progress from multiple threads, * non-progress diagnostics that just scroll by (e.g. logging), * breaking the state apart for individual threads, so they can update their relevant portion of the progress bar without interfering with each other ("zooming"), * smart throttling (no updates drawn when nothing is happening, and only ever drawn at a maximum rate). Here is a very simple example: import Control.Concurrent import System.Progress main = withProgress_ "" id $ \pm -> do -- Set the progress bar: setMeter pm "Working..." -- Do some "work": threadDelay 3000000 -- Print something while temporarily hiding the progress bar: putMsgLn pm "Some extra diagnostics that scrolls by" setMeter pm "Almost done..." threadDelay 1000000 putMsgLn pm "Done." The first argument of 'withProgress_' is the initial state and the second is a renderer for the current state: render :: Int -> String render p = "Progress: " ++ show p ++ "%" withProgress_ 0 render $ \pm -> do threadDelay 1000000 setMeter pm 10 threadDelay 8900000 setMeter pm 99 -- The famous last percent: threadDelay 10000000 putMsgLn pm "Done." Progress-meter will do The Right Thing when you update the state or produce log messages from multiple threads. Happy holidays ertes

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Hackage / Stackage Idea
by alex＠centromere.net 24 Dec '17

24 Dec '17

Hi all, I use Haskell in production, and when choosing a library I wonder, "Is this package production-ready?". In addition to evaluating the quality of the code, I consider various factors such as the most recent upload date, number of downloads, the age of the last commit, the author's reputation, the number of packages which depend on that package, and the number of issues open and closed. I think it would be interesting to add a feature to Hackage and/or Stackage which allows companies to advertise that they use a package in production. If they elect to be anonymous, only the count would increase. I believe that this data would not only help inform my library choices, but also help communicate Haskell's merits to industry. What do you all think? Alex

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Code runs 7x FASTER with profiling
by Neil Mayhew 24 Dec '17

24 Dec '17

I was writing a simple utility and I decided to use regexps to parse filenames. (I know, now I have two problems :-) ) I was surprised at how slow it ran, so I did a profiling build. The profiled code runs reasonably quickly, and is 7x faster, which makes it a bit hard to figure out where the slowdown is happening in the non-profiled code. I’m wondering if I’m doing something wrong, or if there’s a bug in |regex-tdfa| or in ghc. I’ve pared my code down to just the following: |import Text.Regex.TDFA ((=~)) main :: IO () main = do entries <- map parseFilename . lines <$> getContents let check (Right (_, t)) = last t == 'Z' check _ = False print $ all check entries parseFilename :: String -> Either String (String, String) parseFilename fn = case (fn =~ pattern :: [[String]]) of [[_, full, _, time]] -> Right $ (full, time) _ -> Left fn where pattern = "^\\./duplicity-(full|inc|new)(-signatures)?\\.\ \([0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]T[0-9][0-9][0-9][0-9][0-9][0-9]Z)\\." | The relevant part of my |.cabal| file looks like this: |executable DuplicityAnalyzer main-is: DuplicityAnalyzer.hs build-depends: base >=4.6 && <4.11, regex-tdfa >= 1.0 && <1.3 default-language: Haskell2010 ghc-options: -Wall -rtsopts | To run the profiling, I do: |cabal clean cabal configure --enable-profiling cabal build dist/build/DuplicityAnalyzer/DuplicityAnalyzer <names.in +RTS -sprofiling-summary.out -p | The |MUT| time in the non-profiling build is 7x bigger, and the |%GC| time goes from 8% to 21%. I’ve put the actual output in a gist <https://gist.github.com/neilmayhew/247a30738c0e294902e7c2830ca2c6f5>. I’ve also put my test input file there, in case anyone wants to try this themselves. I’ve done my testing with NixOS (ghc 8.0.2) and Debian with the Haskell Platform (ghc 8.2.1) and the results are basically the same. I even tried using Docker containers with Debian Jessie and Debian Stretch, just to eliminate any OS influence, and the results are still the same. I’ve tried it on an i5-2500K, i5-3317U and Xeon E5-1620. I also wrote a dummy implementation of |=~| that ignores the regex pattern and does a hard-coded manual parse, and that produces times just slightly better than the profiled ones. So I don’t think there’s a problem in my outer code that uses |=~|.

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Re: [Haskell-cafe] [ANNOUNCE] GHC 8.4.1-alpha1 available
by Ben Gamari 23 Dec '17

23 Dec '17

George Colpitts <george.colpitts(a)gmail.com> writes: > Probably stating what is obvious and well-know but anyways: > > - On the status page > <https://ghc.haskell.org/trac/ghc/wiki/Status/GHC-8.4.1> it would be > good to have a link for "Phase 2 of the Semigroup-Monoid Proposal (Herbert > Riedel)" Good catch. I've added a link. > - Also IIRC we normally have a page on porting to the new release. It > would be good to have that also when we have a chance. > Indeed, the migration page can be found here: https://ghc.haskell.org/trac/ghc/wiki/Migration/8.4. I've added a link to the 8.4 status page. Cheers, - Ben

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Happy National Mathematics Day
by Henk-Jan van Tuyl 22 Dec '17

22 Dec '17

L.S., Happy National Mathematics Day to everyone in India! Regards, Henk-Jan van Tuyl -- Message from Stanford University: 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://foldingathome.stanford.edu/ -- http://members.chello.nl/hjgtuyl/tourdemonad.html Haskell programming --

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Re: [Haskell-cafe] [ANNOUNCE] GHC 8.4.1-alpha1 available
by Oleg Grenrus 22 Dec '17

22 Dec '17

I copy & paste Hervert's reddit answer here [1], for ones who don't follow it: As the suffix "alpha" implies, this is a very bleeding edge release with very little guarantees regarding API stability (c.f. new GHC schedule [2] <https://ghc.haskell.org/trac/ghc/wiki/WorkingConventions/Releases/NewSchedu…>). Put differently, a package that works now with GHC 8.4.1-alpha1 may not necessarily work with the final GHC 8.4.1 release. In order to support early adopters in testing GHC 8.4.1-alpha, there's a new Overlay Hackage Package Index <https://github.com/hvr/head.hackage> [3] which provides packages patched for unreleased GHCs (currently GHC 8.4.1-alpha1 & GHC 8.5/HEAD). See its README <https://github.com/hvr/head.hackage#README> [4] for instructions on how to use it; there's also a shell script included which automates common workflows; finally there's also support for HEAD.hackage in themake-travis-yml Travis CI script generator <https://github.com/haskell-hvr/multi-ghc-travis>. [5] Don't hesitate to ask if you have questions! As usual, there's already an (incomplete & work-in-progress) GHC 8.4.x Migration Guide <https://ghc.haskell.org/trac/ghc/wiki/Migration/8.4> [6] you can consult and maybe even help complete. Links: - [1]: https://www.reddit.com/r/haskell/comments/7l4b19/announce_ghc_841alpha1_ava… - [2]: https://ghc.haskell.org/trac/ghc/wiki/WorkingConventions/Releases/NewSchedu… - [3]: https://github.com/hvr/head.hackage - [4]: https://github.com/hvr/head.hackage#README - [5]: https://github.com/haskell-hvr/multi-ghc-travis - [6]: https://ghc.haskell.org/trac/ghc/wiki/Migration/8.4 Cheers, Oleg On 21.12.2017 22:16, George Colpitts wrote: > Thanks Ben. I installed the Mac binaries. > > For others who are wondering, you need llvm 5 if you want to use llvm > with this. > > Needless to say, many libraries, e.g. haskell-src-exts, primitive, and > intero won't compile with this even with --allow-newer > > I'll notify those libraries about that in case they want to get > started on 8.4.1 > > Cheers > George > > On Wed, Dec 20, 2017 at 4:48 PM Ben Gamari <ben(a)well-typed.com > <mailto:ben@well-typed.com>> wrote: > > > The GHC development team is pleased to announce the first alpha > release > of the 8.4.1 release. The usual release artifacts are available from > > https://downloads.haskell.org/~ghc/8.4.1-alpha1 > <https://downloads.haskell.org/%7Eghc/8.4.1-alpha1> > > Note that this release drops compatibility with GCC 4.6 and earlier. > While we generally try to place as few constraints on system toolchain > as possible, this release depends upon the __atomic__ builtins > provided > by GCC 4.7 and later (see #14244). > > > === Notes on release scheduling === > > The 8.4.1 release marks the first release where GHC will be > adhering to > its new, higher-cadence release schedule [1]. Under this new scheme, > major releases will be made in 6-month intervals with interstitial > minor > releases as necessary. > > In order to minimize the likelihood of schedule slippage and to ensure > adequate testing, each major release will be preceeded by a number of > regular alpha releases. We will begin issuing these releases roughly > three months before the final date of the major release and will issue > roughly one every two weeks during this period. This high release > cadence will allow us to quickly get fixes in to users hands and allow > better feedback on the status of the release. > > GHC 8.4 is slated to be released in mid-February but, due to technical > constraints, we are starting the alpha-release cycle a bit later than > planned under the above schedule. For this reason, it would be greatly > appreciated if users could put this alpha through its paces to make up > for lost time. > > As always, do let us know if you encounter any trouble in the > course of > testing. Thanks for your help! > > Cheers, > > - Ben > > > [1] https://ghc.haskell.org/trac/ghc/blog/2017-release-schedule > _______________________________________________ > Glasgow-haskell-users mailing list > Glasgow-haskell-users(a)haskell.org > <mailto:Glasgow-haskell-users@haskell.org> > http://mail.haskell.org/cgi-bin/mailman/listinfo/glasgow-haskell-users > > > > _______________________________________________ > ghc-devs mailing list > ghc-devs(a)haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs

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Call for Papers: PACMPL issue ICFP 2018
by Lindsey Kuper 21 Dec '17

21 Dec '17

PACMPL issue ICFP 2018 Call for Papers accepted papers to be invited for presentation at The 23rd ACM SIGPLAN International Conference on Functional Programming St. Louis, Missouri, USA http://icfp18.sigplan.org/ ### Important dates Submissions due: 16 March 2018 (Friday) Anywhere on Earth https://icfp18.hotcrp.com Author response: 2 May (Wednesday) - 4 May (Friday) 14:00 UTC Notification: 18 May (Friday) Final copy due: 22 June (Friday) Conference: 24 September (Monday) - 26 September (Wednesday) ### About PACMPL Proceedings of the ACM on Programming Languages (PACMPL <https://pacmpl.acm.org/>) is a Gold Open Access journal publishing research on all aspects of programming languages, from design to implementation and from mathematical formalisms to empirical studies. Each issue of the journal is devoted to a particular subject area within programming languages and will be announced through publicized Calls for Papers, like this one. ### Scope PACMPL issue ICFP 2018 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. PACMPL issue ICFP 2018 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 principal editor if you have questions or are concerned about the appropriateness of a topic. ### Preparation of submissions **Deadline**: The deadline for submissions is Friday, March 16, 2018, Anywhere on Earth (<https://en.wikipedia.org/wiki/Anywhere_on_Earth>). This deadline will be strictly enforced. **Formatting**: 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 Small" template that is available (in both LaTeX and Word formats) from <https://www.acm.org/publications/authors/submissions>. For authors using LaTeX, a lighter-weight package, including only the essential files, is available from <http://sigplan.org/Resources/Author/#acmart-format>. There is a limit of 27 pages for a full paper or 14 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. See also PACMPL's Information and Guidelines for Authors at <https://pacmpl.acm.org/authors.cfm>. **Submission**: Submissions will be accepted at <https://icfp18.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 14:00 UTC on Wednesday, May 2, 2018, 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 principal editor 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 PACMPL issue ICFP 2018. We anticipate that there will be a need to clarify and expand on this process, and we will maintain a list of frequently asked questions and answers on the conference website to address common concerns. **PACMPL issue ICFP 2018 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 review 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 18, 2018. 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 22, 2018), 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. **PACMPL issue ICFP 2018 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 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 Small 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 submissions will be expected to attend and present their paper at the conference. 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. * 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 <https://icfp18.sigplan.org/track/icfp-2018-Artifacts>. ### Special categories of papers In addition to research papers, PACMPL issue 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 PACMPL issue 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 principal editor will be happy to advise on any concerns about which category to submit to. ### ICFP Organizers General Chair: Robby Findler (Northwestern University, USA) Artifact Evaluation Co-Chairs: Simon Marlow (Facebook, UK) Ryan R. Newton (Indiana University, USA) Industrial Relations Chair: Alan Jeffrey (Mozilla Research, USA) Programming Contest Organiser: Matthew Fluet (Rochester Institute of Technology, USA) Publicity and Web Chair: Lindsey Kuper (Intel Labs, USA) Student Research Competition Chair: Ilya Sergey (University College London, UK) Video Co-Chairs: Jose Calderon (Galois, Inc., USA) Nicolas Wu (University of Bristol, UK) Workshops Co-Chair: David Christiansen (Indiana University, USA) Christophe Scholliers (Universiteit Gent, Belgium) ### PACMPL issue ICFP 2018 Principal Editor: Matthew Flatt (Univesity of Utah, USA) Review Committee: Sandrine Blazy (IRISA, University of Rennes 1, France) David Christiansen (Indiana University, USA) Martin Elsman (University of Copenhagen, Denmark) Marco Gaboardi (University at Buffalo, CUNY, USA) Sam Lindley (University of Edinburgh, UK) Heather Miller (Northweastern University, USA / EPFL, Switzerland) J. Garrett Morris (University of Kansas, USA) Henrik Nilsson (University of Nottingham, UK) François Pottier (Inria, France) Alejandro Russo (Chalmers University of Technology, Sweden) Ilya Sergey (University College London, UK) Michael Sperber (Active Group GmbH, Germany) Wouter Swierstra (Utrecht University, UK) Éric Tanter (University of Chile, Chile) Katsuhiro Ueno (Tohoku University, Japan) Niki Vazou (University of Maryland, USA) Jeremy Yallop (University of Cambridge, UK) External Review Committee: Michael D. Adams (University of Utah, USA) Amal Ahmed (Northeastern University, USA) Nada Amin (University of Cambridge, USA) Zena Ariola (University of Oregon) Lars Bergstrom (Mozilla Research) Lars Birkedal (Aarhus University, Denmark) Edwin Brady ( University of St. Andrews, UK) William Byrd (University of Alabama at Birmingham, USA) Giuseppe Castagna (CRNS / University of Paris Diderot, France) Sheng Chen (University of Louisiana at Lafayette, USA) Koen Claessen (Chalmers University ot Technology, Sweden) Ugo Dal Lago (University of Bologna, Italy / Inria, France) David Darais (University of Vermont, USA) Joshua Dunfield (Queen’s University, Canada) Richard Eisenberg (Bryn Mawr College, USA) Matthew Fluet (Rochester Institute of Technology, USA) Nate Foster (Cornell University, USA) Jurriaan Hage (Utrecht University, Netherlands) David Van Horn (University of Maryland, USA) Zhenjiang Hu (National Institute of Informatics, Japan) Suresh Jagannathan (Purdue University, USA) Simon Peyton Jones (Microsoft Research, UK) Naoki Kobayashi (University of Tokyo, Japan) Neelakantan Krishnaswami (University of Cambridge, UK) Kazutaka Matsuda (Tohoku University, Japan) Trevor McDonell (University of New South Wales, Australia) Hernan Melgratti (University of Buenos Aires, Argentina) Akimasa Morihata (University of Tokyo, Japan) Aleksandar Nanevski (IMDEA Software Institute, Spain) Kim Nguyễn (University of Paris-Sud, France) Cosmin Oancea (DIKU, University of Copenhagen, Denmark) Bruno C. d. S. Oliveira (University of Hong Kong, China) Tomas Petricek (University of Cambridge, UK) Benjamin Pierce (University of Pennsylvania, USA) Christine Rizkallah (University of Pennsylvania, USA) Tom Schrijvers (KU Leuven, Belgium) Manuel Serrano (Inria, France) Jeremy Siek (Indiana University, USA) Josef Svenningsson (Chalmers University of Technology, Sweden) Nicolas Tabareau (Inria, France) Dimitrios Vytiniotis (Microsoft Research, UK) Philip Wadler (University of Edinburgh, UK) Meng Wang (University of Kent, UK)

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Re: [Haskell-cafe] Are bottoms ever natural?
by Alexey Muranov 21 Dec '17

21 Dec '17

Siddharth, how would you deal with functions that terminate for some arguments/inputs but do not terminate for the others ? Alexey. On Tue, 2017-12-19 at 07:20 +0000, (IIIT) Siddharth Bhat wrote: > > Is that really true, though? > > Usually when you have an infinite loop, you have progress of some > > sort. Infinite loops with no side effects can be removed from the > > program according to the C standard, for example. So, in general, we > > should allow programmers to express termination / progress, right? > At > > that point, no computation ever "bottoms out"? > > Shouldn't a hypothetical purely functional programming language > > better control this (by eg. Forcing totality?) It seems like we lose > > much of the benefits of purity by muddying the waters with > > divergence. > > From an optimising compiler perspective, Haskell is on some weird > > lose-lose space, where you lose out on traditional compiler > > techniques that work on strict code, but it also does not allow the > > awesome stuff you could do with "pure" computation because bottom > > lurks everywhere. > > What neat optimisations can be done on Haskell that can't be done in > > a traditional imperative language? I genuinely want to know. > > What are your thoughts on this? > > Cheers > > Siddharth > > > > On Tue 19 Dec, 2017, 08:09 Brandon Allbery, <allbery.b(a)gmail.com> > > wrote: >> > > Define "natural". >> > > >> > > You might want to look into the concept of Turing completeness. >> One >> > > could define a subset of Haskell in which bottoms cannot occur... >> > > but it turns out there's a lot of useful things you can't do in >> > > such a language. (In strict languages, these often are expressed >> as >> > > infinite loops of one kind or another. Note also that any >> > > dependency on external input is an infinite loop from the >> > > perspective of the language, since it can only be broken by the >> > > external entity providing the input.) >> > > >> > > On Tue, Dec 19, 2017 at 1:47 AM, (IIIT) Siddharth Bhat >> <siddharth.b >> > > hat(a)research.iiit.ac.in> wrote: >>> > > > I've been thinking about the issue of purity and speculation >>> > > > lately, and from what little I have read, it looks like the >>> > > > presence of bottom hiding inside a lazy value is a huge issue. >>> > > > >>> > > > How "natural" is it for bottoms to exist? If one were to >>> change >>> > > > Haskell and declare that any haskell value can be speculated >>> > > > upon, what ramifications does this have? >>> > > > >>> > > > Is it totally broken? Is it "correct" but makes programming >>> > > > unpleasant? What's the catch? >>> > > > >>> > > > Thanks, >>> > > > Siddharth

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