February 2018 - Haskell-Cafe

Re: [Haskell-cafe] avoiding parens in postfix applicative notation
by Johannes Waldmann 07 Feb '18

07 Feb '18

Thanks for comments and suggestions. > The lens library defines (<&>) with very low precedence Yes. I guess my question was: Why? > f <$> foo <*> bar where f x y = ... I avoid "where" because * it uses an identifier before it is defined * it is not as composable as "let", which is an expression, but "where" can only be attached to declarations - I can write 1 + let x = 3 in x but not 1 + ( x where x = 3 ) - J.W.

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avoiding parens in postfix applicative notation
by Johannes Waldmann 07 Feb '18

07 Feb '18

Dear Cafe - operators <$> and <*> have their precedence so that this (silly example) works without parens: (,) <$> "foo" <*> "bar" Most of the time, I find that the function (the first argument) is the largest sub-expression, so I want to put it last. I can do this import Control.Lens.Lens ((<&>)) "foo" <**> ( "bar" <&> (,) ) but (even ignoring that this pulls in a library with a ton of dependencies) this needs parens, and I find this quite ugly when the closing parenthesis comes at the end of lambda expression that spans several lines. One work-around is ( "foo" <**> ) $ "bar" <&> (,) Can this be done in a less noisy way? - J.W. PS: Bike-sheddingly, shouldn't this (<&>) be defined right next to (<$>) ? There's nothing that would tie it to lenses? And, (&) right next to ($) ?

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[ANNOUNCE] GHC 8.4.1-alpha3 available
by Ben Gamari 06 Feb '18

06 Feb '18

The GHC development team is pleased to announce the third and likely last alpha release leading up to GHC 8.4.1. The usual release artifacts are available from https://downloads.haskell.org/~ghc/8.4.1-alpha3 Due to user demand we now offer a binary distribution for 64-bit Fedora 27, which links against ncurses6. This is in contrast to the Debian 8 distribution, which links against ncurses5. Users of newer distributions (Fedora 27, Debian Sid) should use this new Fedora 27 distribution. Also due to user demand we have reintroduced compatibility with GCC 4.4, which earlier alphas had dropped due to #14244. Note that this release is still affected by #14675, wherein the compiler will segmentation fault when built with some Ubuntu toolchains. We are actively working to identify the cause and hope that this will be resolved before the final release. === 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 preceded 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 into users' hands and more quickly identify potential issues. 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

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Re: [Haskell-cafe] rolling span and groupBy for lists
by Harendra Kumar 05 Feb '18

05 Feb '18

On 5 February 2018 at 12:22, Evan Laforge <qdunkan(a)gmail.com> wrote: > I have my own list library with a bunch of things like this. I think > it's what most people do, and some upload them to hackage, e.g. > utility-ht or the split package, or data-ordlist. > The irony is that theoretically you can find a Haskell package or implementation of whatever you can imagine but quite often it takes more time to discover it than writing your own. And then uploading what you wrote to hackage compounds the problem. A hoogle search only shows the groupBy in base, signature search also does not yield other results, it seems hoogle does not cover those other packages. After writing my own and spending quite a bit of time I could find two other similar implementations of groupBy, one in "utility-ht" package and the other in "data-list-sequences" but they don't turn up in hoogle search. It looks like hoogle database should cover more packages, or maybe the search has some issues. This state of affairs encourages people to write their own rather than find and reuse stuff. My example in this email can be dismissed as a small one but I think it is a larger problem. > You can probably find something like this in 'split', or if not, that > might be a good place to contribute it. > Yes, that is the fallback option I was considering, split seems to be the most comprehensive of all such list related packages. > I have a bunch of grouping functions too, which I use all the time, so > if there's some kind of general list grouping package then maybe I > could put them there. > It will be a great service to other Haskell explorers if we can consolidate all such packages and make one standard package covering most use cases and deprecate the other packages. Also it may be a good idea to have a see-also or related packages kind of field in packages so that discovery is easy. > On the other hand, this sort of thing is pretty individual, so it > doesn't seem so bad for each person to have their own local library. > That way you know it fits your style. Ultimately I think that's why > none of the split functions made it into Data.List, every person has a > slightly different idea of what it should be. > I thought that rollingGroupBy would have been a better default option as it can practically subsume the purpose of groupBy. groupBy in base is not well documented, and intuitively many think it works the way rollingGroupBy works i.e. compare two successive elements rather than comparing a fixed element. See this stack overflow question https://stackoverflow.com/questions/45654216/haskell-groupby-function-how-e… , I thought the same way. I guess if we compare two successive elements, by transitive equality the existing groupBy implementation will practically get covered by that, not strictly compatible but should serve all practical purposes. That was the point why I was asking to consider having it in base alongside groupBy. It seems more useful, general and intuitive than the existing groupBy. -harendra > > On Sun, Feb 4, 2018 at 7:50 PM, Harendra Kumar <harendra.kumar(a)gmail.com> > wrote: > > Hi, > > > > For a small problem, I was looking for a groupBy like function that > groups > > based on a predicate on successive elements but I could not find one. I > > wrote these little functions for that purpose: > > > > -- | Like span, but with a predicate that compares two successive > elements. > > The > > -- span ends when the two successive elements do not satisfy the > predicate. > > rollingSpan :: (a -> a -> Bool) -> [a] -> ([a], [a]) > > rollingSpan _ xs@[] = (xs, xs) > > rollingSpan _ xs@[_] = (xs, []) > > rollingSpan p (x1:xs@(x2:_)) > > | p x1 x2 = > > let (ys, zs) = rollingSpan p xs > > in (x1 : ys, zs) > > | otherwise = ([x1], xs) > > > > -- | Like 'groupBy' but with a predicate that compares two successive > > elements. > > -- A group ends when two successive elements do not satisfy the > predicate. > > rollingGroupBy :: (a -> a -> Bool) -> [a] -> [[a]] > > rollingGroupBy _ [] = [] > > rollingGroupBy cmp xs = > > let (ys, zs) = rollingSpan cmp xs > > in ys : rollingGroupBy cmp zs > > > > Are there any existing functions that serve this purpose or is there any > > simpler way to achieve such functionality? If not, where is the right > place > > for these, if any. Can they be included in Data.List in base? > > > > Thanks, > > Harendra > > > > _______________________________________________ > > ghc-devs mailing list > > ghc-devs(a)haskell.org > > http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs > > >

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WST 2018 - 1st Call for Papers (submission: April 15, 2018)
by Salvador Lucas 05 Feb '18

05 Feb '18

========================================================================== WST 2018 - Call for Papers 16th International Workshop on Termination July 18-19, 2017, Oxford, United Kingdom http://wst2018.webs.upv.es/ ========================================================================== The Workshop on Termination (WST) traditionally brings together, in an informal setting, researchers interested in all aspects of termination, whether this interest be practical or theoretical, primary or derived. The workshop also provides a ground for cross-fertilization of ideas from the different communities interested in termination (e.g., working on computational mechanisms, programming languages, software engineering, constraint solving, etc.). The friendly atmosphere enables fruitful exchanges leading to joint research and subsequent publications. The workshop is held as part of the 2018 Federated Logic Conference (FLoC 2018) http://www.floc2018.org/ IMPORTANT DATES: * submission deadline: April 15, 2018 * notification: May 15, 2018 * final version due: May 31, 2018 * workshop: July 18-19, 2018 TOPICS: The 16th International Workshop on Termination welcomes contributions on all aspects of termination. In particular, papers investigating applications of termination (for example in complexity analysis, program analysis and transformation, theorem proving, program correctness, modeling computational systems, etc.) are very welcome. Topics of interest include (but are not limited to): * abstraction methods in termination analysis * certification of termination and complexity proofs * challenging termination problems * comparison and classification of termination methods * complexity analysis in any domain * implementation of termination methods * non-termination analysis and loop detection * normalization and infinitary normalization * operational termination of logic-based systems * ordinal notation and subrecursive hierarchies * SAT, SMT, and constraint solving for (non-)termination analysis * scalability and modularity of termination methods * termination analysis in any domain (lambda calculus, declarative programming, rewriting, transition systems, etc.) * well-founded relations and well-quasi-orders COMPETITION: Since 2003, the catalytic effect of WST to stimulate new research on termination has been enhanced by the celebration of the Termination Competition and its continuously developing problem databases containing thousands of programs as challenges for termination analysis in different categories, see http://termination-portal.org/wiki/Termination_Competition In 2018, the Termination Competition will run in parallel with FLoC 2018. More details will be provided in a dedicated announcement on the competition. PROGRAM COMMITTEE: Cristina Borralleras - U. de Vic Ugo Dal Lago - U. degli Studi di Bologna Carsten Fuhs - Birkbeck, U. of London Samir Genaim - U. Complutense de Madrid Juergen Giesl - RWTH Aachen Raul Gutiérrez - U. Politecnica de València Keiichirou Kusakari - Gifu University Salvador Lucas (chair) - U. Politecnica de Valencia Fred Mesnard - U. de La Reunion Aart Middeldorp - U. of Innsbruck Albert Rubio - U. Politecnica de Catalunya Rene Thiemann - U. of Innsbruck Caterina Urban - ETH Zürich INVITED SPEAKERS: tba SUBMISSION: Submissions are short papers/extended abstracts which should not exceed 5 pages. There will be no formal reviewing. In particular, we welcome short versions of recently published articles and papers submitted elsewhere. The program committee checks relevance and provides additional feedback for each submission. The accepted papers will be made available electronically before the workshop. Papers should be submitted electronically via the submission page: https://easychair.org/conferences/?conf=wst2018 Please, use LaTeX and the LIPIcs style file http://drops.dagstuhl.de/styles/lipics/lipics-authors.tgz to prepare your submission.

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Yesod with lts-10.4
by Yotam Ohad 05 Feb '18

05 Feb '18

Hi, I'm trying to install yesod using stack and lts-10.4, but I get the following result: stack install yesod aeson-1.2.3.0: configure aeson-1.2.3.0: build Progress: 1/26 -- While building custom Setup.hs for package aeson-1.2.3.0 using: /home/yotam/.stack/setup-exe-cache/i386-linux-nopie/Cabal-simple_mPHDZzAJ_2.0.1.0_ghc-8.2.2 --builddir=.stack-work/dist/i386-linux-nopie/Cabal-2.0.1.0 build --ghc-options " -ddump-hi -ddump-to-file -fdiagnostics-color=always" Process exited with code: ExitFailure 1 Logs have been written to: /home/yotam/TheMafsidan/.stack-work/logs/aeson-1.2.3.0.log Configuring aeson-1.2.3.0... Preprocessing library for aeson-1.2.3.0.. Building library for aeson-1.2.3.0.. [ 1 of 24] Compiling Data.Aeson.Compat ( Data/Aeson/Compat.hs, .stack-work/dist/i386-linux-nopie/Cabal-2.0.1.0/build/Data/Aeson/Compat.o ) [ 2 of 24] Compiling Data.Aeson.Internal.Functions ( Data/Aeson/Internal/Functions.hs, .stack-work/dist/i386-linux-nopie/Cabal-2.0.1.0/build/Data/Aeson/Internal/Functions.o ) [ 3 of 24] Compiling Data.Aeson.Parser.UnescapePure ( pure/Data/Aeson/Parser/UnescapePure.hs, .stack-work/dist/i386-linux-nopie/Cabal-2.0.1.0/build/Data/Aeson/Parser/UnescapePure.o ) [ 4 of 24] Compiling Data.Aeson.Parser.Unescape ( Data/Aeson/Parser/Unescape.hs, .stack-work/dist/i386-linux-nopie/Cabal-2.0.1.0/build/Data/Aeson/Parser/Unescape.o ) [ 5 of 24] Compiling Data.Aeson.Types.Generic ( Data/Aeson/Types/Generic.hs, .stack-work/dist/i386-linux-nopie/Cabal-2.0.1.0/build/Data/Aeson/Types/Generic.o ) [ 6 of 24] Compiling Data.Aeson.Types.Internal ( Data/Aeson/Types/Internal.hs, .stack-work/dist/i386-linux-nopie/Cabal-2.0.1.0/build/Data/Aeson/Types/Internal.o ) [ 7 of 24] Compiling Data.Aeson.Parser.Internal ( Data/Aeson/Parser/Internal.hs, .stack-work/dist/i386-linux-nopie/Cabal-2.0.1.0/build/Data/Aeson/Parser/Internal.o ) [ 8 of 24] Compiling Data.Aeson.Parser ( Data/Aeson/Parser.hs, .stack-work/dist/i386-linux-nopie/Cabal-2.0.1.0/build/Data/Aeson/Parser.o ) [ 9 of 24] Compiling Data.Attoparsec.Time.Internal ( attoparsec-iso8601/Data/Attoparsec/Time/Internal.hs, .stack-work/dist/i386-linux-nopie/Cabal-2.0.1.0/build/Data/Attoparsec/Time/Internal.o ) [10 of 24] Compiling Data.Attoparsec.Time ( attoparsec-iso8601/Data/Attoparsec/Time.hs, .stack-work/dist/i386-linux-nopie/Cabal-2.0.1.0/build/Data/Attoparsec/Time.o ) [11 of 24] Compiling Data.Aeson.Parser.Time ( Data/Aeson/Parser/Time.hs, .stack-work/dist/i386-linux-nopie/Cabal-2.0.1.0/build/Data/Aeson/Parser/Time.o ) [12 of 24] Compiling Data.Aeson.Types.FromJSON ( Data/Aeson/Types/FromJSON.hs, .stack-work/dist/i386-linux-nopie/Cabal-2.0.1.0/build/Data/Aeson/Types/FromJSON.o ) /tmp/stack15763/aeson-1.2.3.0/Data/Aeson/Types/FromJSON.hs:108:1: error: Bad interface file: /home/yotam/.stack/snapshots/i386-linux-nopie/lts-10.4/8.2.2/lib/i386-linux-ghc-8.2.2/time-locale-compat-0.1.1.3-EeYCrKbfyeWLGJYmfXhrGy/Data/Time/Locale/Compat.hi Data.Binary.getPrim: end of file | 108 | import Data.Time.Locale.Compat (defaultTimeLocale) | ^^ Is this a matter of just waiting for packages to update to 8.2.2 or is it something I can change myself? Yotam

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Second Call for Papers: PACMPL issue ICFP 2018
by Lindsey Kuper 05 Feb '18

05 Feb '18

PACMPL Volume 2, 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](https://pacmpl.acm.org/) 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: open access on payment of a fee (**recommended**, and SIGPLAN can cover the cost as described next); copyright transfer to ACM; or retaining copyright but granting ACM exclusive publication rights. Further information about ACM author rights is available from <http://authors.acm.org>. * PACMPL is a Gold Open Access journal. It will be archived in ACM’s Digital Library, but no membership or fee is required for access. Gold Open Access has been made possible by generous funding through ACM SIGPLAN, which will cover all open access costs in the event authors cannot. Authors who can cover the costs may do so by paying an Article Processing Charge (APC). PACMPL, SIGPLAN, and ACM Headquarters are committed to exploring routes to making Gold Open Access publication both affordable and sustainable. * ACM offers authors a range of copyright options, one of which is Creative Commons CC-BY publication; this is the option recommended by the PACMPL editorial board. A reasoned argument in favour of this option can be found in the article [Why CC-BY?](https://oaspa.org/why-cc-by/) published by OASPA, the Open Access Scholarly Publishers Association. * We intend that the papers 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. * 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. * The official publication date is the date the papers 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 an Artifact Evaluation Committee, separate from the paper Review 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 papers, 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 papers 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 review 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 Volume 2, 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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Fwd: rolling span and groupBy for lists
by Harendra Kumar 05 Feb '18

05 Feb '18

Hi, I am looking for the decision making authority or a place where questions about haskell libraries like in the email below can be asked or answered. ghc-devs told me that their list is not the right place for this and redirected me to haskell-cafe or libraries(a)haskell.org. I tried sending an email to libraries(a)haskell.org but that seems to be a closed list, my email got rejected, so that also does not seem like the right place. Is haskell cafe the right place? I was under the impression that haskell-cafe is for general discussions and not an owner of any of the libraries or any other haskell code. Are there any other mailing lists that I am missing? I can raise a ticket at ghc trac but I guess that cannot be the primary way to ask simple questions. -harendra ---------- Forwarded message ---------- From: <libraries-owner(a)haskell.org> Date: 5 February 2018 at 09:34 Subject: Re: rolling span and groupBy for lists To: harendra.kumar(a)gmail.com You are not allowed to post to this mailing list, and your message has been automatically rejected. If you think that your messages are being rejected in error, contact the mailing list owner at libraries-owner(a)haskell.org. ---------- Forwarded message ---------- From: Harendra Kumar <harendra.kumar(a)gmail.com> To: David Feuer <david(a)well-typed.com>, libraries <libraries(a)haskell.org> Cc: ghc-devs(a)haskell.org Bcc: Date: Mon, 5 Feb 2018 10:07:55 +0530 Subject: Re: rolling span and groupBy for lists I was mainly asking if it makes sense to include these functions in base/Data.List. Since the base package is maintained and ships along with ghc, and the issues are also raised at ghc trac I thought this is the right list. I am copying to libraries(a)haskell.org as well. -harendra On 5 February 2018 at 09:53, David Feuer <david(a)well-typed.com> wrote: > This is the wrong list. You probably meant to email haskell-cafe or > perhaps libraries(a)haskell.org. > > > > David Feuer > Well-Typed, LLP > > -------- Original message -------- > From: Harendra Kumar <harendra.kumar(a)gmail.com> > Date: 2/4/18 10:50 PM (GMT-05:00) > To: ghc-devs(a)haskell.org > Subject: rolling span and groupBy for lists > > Hi, > > For a small problem, I was looking for a groupBy like function that groups > based on a predicate on successive elements but I could not find one. I > wrote these little functions for that purpose: > > -- | Like span, but with a predicate that compares two successive elements. > The > -- span ends when the two successive elements do not satisfy the predicate. > rollingSpan :: (a -> a -> Bool) -> [a] -> ([a], [a]) > rollingSpan _ xs@[] = (xs, xs) > rollingSpan _ xs@[_] = (xs, []) > rollingSpan p (x1:xs@(x2:_)) > | p x1 x2 = > let (ys, zs) = rollingSpan p xs > in (x1 : ys, zs) > | otherwise = ([x1], xs) > > -- | Like 'groupBy' but with a predicate that compares two successive > elements. > -- A group ends when two successive elements do not satisfy the predicate. > rollingGroupBy :: (a -> a -> Bool) -> [a] -> [[a]] > rollingGroupBy _ [] = [] > rollingGroupBy cmp xs = > let (ys, zs) = rollingSpan cmp xs > in ys : rollingGroupBy cmp zs > > Are there any existing functions that serve this purpose or is there any > simpler way to achieve such functionality? If not, where is the right place > for these, if any. Can they be included in Data.List in base? > > Thanks, > Harendra >

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Call for Participation: BOB 2018 (February 23, Berlin)
by Stefan Wehr 03 Feb '18

03 Feb '18

There are several Haskell-related talks and tutorials, see below for details! ================================================================ BOB 2018 Conference “What happens if we simply use what’s best?” February 23, 2018, Berlin http://bobkonf.de/2018/ Program: http://bobkonf.de/2018/en/program.html Registration: http://bobkonf.de/2018/en/registration.html ================================================================ BOB is the conference for developers, architects and decision-makers to explore technologies beyond the mainstream in software development, and to find the best tools available to software developers today. Our goal is for all participants of BOB to return home with new insights that enable them to improve their own software development experiences. The program features 14 talks and 8 tutorials on current topics: http://bobkonf.de/2018/en/program.html The subject range of talks includes functional programming, verticalization, formal methods, and data analytics. There will be two talks about Haskell: * Testing monadic programs using QuickCheck and state machine based models * New Hasql - a native Haskell Postgres driver faster than C The tutorials feature introductions to Haskell, Clojure, Livecoding, terminal programming in Haskell, Liquid Haskell, functional reactive programming, and domain-driven design. Leif Andersen will give the keynote talk. Registration is open online: http://bobkonf.de/2018/en/registration.html BOB cooperates with the :clojured conference on the following day. There is a registration discount available for participants of both events. http://www.clojured.de/

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MonadBaseControl and Freer
by Lana Black 02 Feb '18

02 Feb '18

Hello, I have a problem with implementing a MonadBaseControl instance for freer monad (Eff from extensible-effects). Specifically, I don't really get what the associated type StM should be. As far as I understand, MonadBaseControl class does the following: captures the current state. Performs the action passed to lifeBaseWith or other wrapper functions. Returns the result wrapped in the captured state. Here's the instance I could come up with. instance (MonadBase m (Eff r), Typeable m, SetMember Lift (Lift m) r) => MonadBaseControl m (Eff r) where type StM (Eff r) a = Eff r a liftBaseWith f = lift (f return) restoreM = id It obviously doesn't work, but I currently have no idea how to fix it, because `Eff r a' contains the state that needs to be captured and cannot be decomposed without losing data as far as I can see. The code can be found in this branch: https://github.com/greydot/extensible-effects/tree/monadbasecontrol As a side matter, I couldn't find any tests for MonadBaseControl instances, and monad-control package itself lacks any tests whatsoever. I'm curious whether there's a way to test instance correctness without plugging it into working code, e.g. something using lifted-base, and hoping for the best.

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