November 2023 - Haskell-Cafe

Does the constraints library give (a :- b) -> Dict (a |- b)?
by Tom Ellis 01 Dec '23

01 Dec '23

The constraints library [1] has implied :: forall a b. (a => b) => a :- b from which I can obtain implied' :: Dict (a |- b) -> a :- b implied' Dict = implied but can I get the converse of this, that is coimplied :: (a :- b) -> Dict (a |- b) coimplied = error "Can it be done?" I don't see how. The library itself only mentions "|-" in its definition. Would this combinator violate some guarantee that's essential for the safe use of type classes? I'm a bit confused why the same library allows abstraction over type variables with forall_[2] forall_ :: (forall a. Dict (p a)) -> Dict (Forall p) but not abstraction over "term" variables (i.e. of kind Constraint), as in coimplied. Alternatively, can someone help me achieve my goal another way? That is, I need to be able to dischange the quantified constraint forall i. T0 i => T2 i given that I can already discharge the constraint forall i. T1 i => T2 i and I have available the value forall i. T0 i => Dict (T1 i) >From the latter I can easily get forall i. T0 i :- T1 i But without coimplied I don't know how to proceed. Thanks, Tom [1] https://hackage.haskell.org/package/constraints-0.14/docs/Data-Constraint-F… [2] https://hackage.haskell.org/package/constraints-0.14/docs/Data-Constraint-F…

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[ANNOUNCE] Agda 2.6.4.1
by Andreas Abel 30 Nov '23

30 Nov '23

Dear all, The Agda Team is pleased to announce Agda 2.6.4.1. Agda 2.6.4.1 is a minor release of Agda 2.6.4 featuring a few changes: - Make recursion on proofs legal again (regression in 2.6.4). - Improve performance, e.g. by removing debug printing unless built with cabal flag `debug`. - Switch to XDG directory convention. - Reflection: change to order of results returned by `getInstances`. - Fix some internal errors. - Fix some issues with `opaque`. # GHC supported versions Agda 2.6.4.1 has been tested with GHC 9.8.1, GHC 9.6.3, 9.4.7, 9.2.8, 9.0.2, 8.10.7, 8.8.4 and 8.6.5 on Linux, macOS and Windows. # Installation Agda 2.6.4.1 can be installed using cabal-install or stack: 1. Getting the tarball $ cabal update $ cabal get Agda-2.6.4.1 $ cd Agda-2.6.4.1 2. a. Using cabal-install $ cabal install -f +optimise-heavily -f +enable-cluster-counting 2. b. Using stack $ stack --stack-yaml stack-a.b.c.yaml install --flag Agda:optimise-heavily --flag Agda:enable-cluster-counting replacing `a.b.c` with your version of GHC. The flags mean: - optimise-heavily: Turn on extra optimisation for a faster Agda. Takes large resources during compilation of Agda. - enable-cluster-counting: Enable unicode clusters for alignment in the LaTeX backend. Requires the ICU lib to be installed and known to pkg-config. These flags can be dropped from the install if causing trouble. # Standard library You can use standard library v1.7.3 or v2.0 (soon to be released) of the standard library with Agda 2.6.4.1. # Fixed issues over Agda 2.6.4 https://hackage.haskell.org/package/Agda-2.6.4.1/changelog Enjoy Agda! Andreas, on behalf of the Agda Team -- Andreas Abel <>< Du bist der geliebte Mensch. Department of Computer Science and Engineering Chalmers and Gothenburg University, Sweden andreas.abel(a)gu.se http://www.cse.chalmers.se/~abela/

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Strange quirk with {} syntax?
by Noon van der Silk 30 Nov '23

30 Nov '23

Sometimes I have a type like: data A = A1 Int | A2 Int Int Then if I want to do pattern matching and ignore the parameters I do: f (A1 _) = .. f (A2 _ _) = ... But that's annoying; I need to remember how many parameters each one has! Yesterday I learned I can just do this: f A1 {} = ... f A2 {} = ... And GHC is happy. Is this expected? Am I the last to learn about this trick? -- Noon van der Silk, ن http://silky.github.io/ "My programming language is kindness."

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ICFP 2024: Call for Papers
by ICFP Publicity 30 Nov '23

30 Nov '23

PACMPL Volume 7, Issue ICFP 2024 Call for Papers Accepted papers to be invited for presentation at The 29th ACM SIGPLAN International Conference on Functional Programming Milan, Italy ### Important dates (All dates are in 2023 at 11.59pm Anywhere on Earth.) Paper Submission -- Wed 28 Feb 2024 (AOE) Paper Author Response -- Mon 29 Apr 12:00 - Wed 1 May 12:00 2024 Paper Notification --Mon 20 May 2024 ### NEW THIS YEAR ------------------- * Full double blind reviewing ### Scope ------------------- PACMPL issue ICFP 2024 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; modularity; components and composition; meta-programming; macros; pattern matching; type systems; type inference; dependent types; effect types; gradual types; refinement types; session types; interoperability; domain-specific languages; imperative programming; object-oriented programming; logic programming; probabilistic programming; reactive programming; generic programming; bidirectional programming. * Implementation: abstract machines; virtual machines; interpretation; compilation; compile-time and run-time optimisation; garbage collection and memory management; runtime systems; 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; build systems; program synthesis. * Foundations: formal semantics; lambda calculus; program equivalence; rewriting; type theory; logic; category theory; computational effects; continuations; control; state; names and binding; program verification. * 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; scientific and numerical computing; graphical user interfaces; graphics and multimedia; GPU programming; scripting; system administration; security. * Education: teaching introductory 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 2024 also welcomes submissions in two separate categories — Functional Pearls and Experience Reports — that must be marked as such when submitted and that need not report original research results. Detailed guidelines on both categories are given at the end of this call. In an effort to achieve a balanced, diverse program, each author may be listed as a (co)author on a maximum of four submissions. Submissions from underrepresented groups are encouraged. Authors who require financial support to attend the conference can apply for PAC funding ( http://www.sigplan.org/PAC/) The General Chair and PC Chair may not submit papers. PC members (other than the PC Chair) may submit papers. Please contact the Program Chair if you have questions or are concerned about the appropriateness of a topic. ### Full Double-Blind Reviewing Process ICFP 2024 will use a full double-blind reviewing process (similar to the one used for POPL 2024 but different from the lightweight double-blind process used in previous years). This means that identities of authors will not be made visible to reviewers until after conditional-acceptance decisions have been made, and then only for the conditionally-accepted papers. The use of full double-blind reviewing has several consequences for authors. * Submissions: Authors must omit their names and institutions from their paper submissions. In addition, references to authors’ own prior work should be in the third person (e.g., not “We build on our previous work …” but rather “We build on the work of …”). * Supplementary material: Authors are permitted to provide supplementary material (e.g., detailed proofs, proof scripts, system implementations, or experimental data) along with their submission, which reviewers may (but are not required to) examine. This material may take the form of a single file, such as a PDF or a tarball. Authors must fully anonymize any supplementary material. Links to supplementary material on external websites are not permitted. * Author response: In responding to reviews, authors should not say anything that reveals their identity, since author identities will not be revealed to reviewers at that stage of the reviewing process. * Dissemination of work under submission: Authors are welcome to disseminate their ideas and post draft versions of their paper(s) on their personal website, institutional repository, or arXiv (reviewers will be asked to turn off arXiv notifications during the review period). But authors should not take steps that would almost certainly reveal their identities to members of the Program Committee, e.g., directly contacting PC members or publicizing the work on widely-visible social media or major mailing lists used by the community. The purpose of the above restrictions is to help the Program Committee and external reviewers come to a judgment about the paper without bias, not to make it impossible for them to discover the authors’ identities if they were to try. In particular, nothing should be done in the name of anonymity that weakens the quality of the submission. However, there are occasionally cases where adhering to the above restrictions is truly difficult or impossible for one reason or another. In such cases, the authors should contact the Program Chair to discuss the situation and how to handle it. ### Preparation of submissions ------------------------------- * Deadline: The deadline for submissions is Wednesday, 28 February , 2024, Anywhere on Earth (https://www.timeanddate.com/time/zones/aoe) 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. There is a limit of 25 pages for a full paper or Functional Pearl and 12 pages for an Experience Report; in either case, the bibliography and an optional clearly marked appendix will not be counted against these limits. 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://icfp24.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 12:00 (noon) AOE on Monday, 29 April, 2024, to read reviews and respond to them. * Appendix and Supplementary Material: Authors have the option to include a clearly marked appendix and/or to attach supplementary material to a submission, on the understanding that reviewers may choose not to look at such an appendix or supplementary material. Supplementary material may be uploaded as a separate PDF document or tarball. Any supplementary material must be uploaded at submission time, not by providing a URL in the paper that points to an external repository. All supplementary material must be anonymised. * 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. * ORCID: ORCID provides a persistent digital identifier (an ORCID iD) that you own and control, and that distinguishes you from every other researcher: https://orcid.org/. ACM now require an ORCID iD for every author of a paper, not just the corresponding author. So, the author who is filling out the permission form should make sure they have the ORCID iDs for all of their coauthors before filling out the form. Any authors who do not yet have an ORCID iD can go to https://orcid.org/register to have one assigned. ### 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 2024. New this year, ICFP 2024 will adapt a full double-blind reviewing process. More information see below. ICFP 2024 will have an Associate Chair who will help the PC Chair monitor reviews, solicit external expert reviews for submissions when there is not enough expertise on the committee, and facilitate reviewer discussions. PACMPL issue ICFP 2024 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. As a result of the review process, a set of papers will be conditionally accepted and all other papers will be rejected. Authors will be notified of these decisions on 20 May, 2024. Authors of conditionally accepted papers will be provided with committee reviews along with a set of mandatory revisions. By 11 June, 2024, the authors should provide a second revised 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 feasibly be addressed within three weeks. 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. ### Information for Authors of Accepted Papers ---------------------------------------------- As a condition of acceptance, final versions of all papers must adhere to the ACM Small format. The page limit for the final versions of papers will be increased by two pages to help authors respond to reviewer comments and mandatory revisions: 27 pages plus bibliography for a regular paper or Functional Pearl, 14 pages plus bibliography for an Experience Report. Authors of accepted submissions will be required to agree to one of the three ACM licensing 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? published by OASPA, the Open Access Scholarly Publishers Association. The other options are copyright transfer to ACM or retaining copyright but granting ACM exclusive publication rights. PACMPL is a Gold Open Access journal, and authors are encouraged to publish their work under a CC-BY license. Gold Open Access guarantees permanent free online access to the definitive version in the ACM Digital Library, and the recommended CC-BY option also allows anyone to copy and distribute the work with attribution. 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 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 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. Authors of each accepted submission are invited to attend and be available for the presentation of that paper at the conference. The schedule for presentations will be determined and shared with authors after the full program has been selected. ### 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. ### 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-specialised 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 describe the experience of using functional programming in practice, whether in industrial application, tool development, programming education, or any other area. 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 end with the words “(Experience Report)” in parentheses. 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 understand the application 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 describes an illuminating experience with functional programming, or provides evidence for a clear thesis about the use of functional programming. The experience or 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 paper to illuminate some aspect of the use of functional programming. 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, papers that show how functional programming was used are more convincing than papers that say only that functional programming was used. It can be especially effective to present comparisons of the situations before and after the experience described in the paper, but other kinds of evidence would also make sense, depending on context. Experience 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. For an industrial project, it should make a claim about how well functional programming worked and why; for a pedagogy paper, it might make a claim about the suitability of a particular teaching style or educational exercise. Either way, it should produce evidence to substantiate the claim. If functional programming worked in this case in the same ways it has worked for others, the paper need only summarise 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 experience and its implementation, but the paper should characterise it and its context well enough so that readers can judge to what degree this experience is relevant to their own circumstances. The paper should take care to highlight any unusual aspects; specifics about the experience are more valuable than generalities about functional programming. 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 to submit 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. ### 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 publicised Calls for Papers, like this one. ### ICFP Organisers General Chair: Marco Gaboardi (Boston University, USA) Programme Chair: Brigitte Pientka (McGill University, Canada) Associate Programme Chair: Gabriele Keller (Utrecht University, Netherlands) Publicity Chair: Ilya Sergey (National University of Singapore, Singapore) Programme Committee: https://icfp24.sigplan.org/committee/icfp-2024-papers-icfp-papers-and-events -----------------------------------------------------------------------

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[TFP 2024 Final Call for Papers] 25th International Symposium on Trends in Functional Programming
by Peter Achten 30 Nov '23

30 Nov '23

# TFP 2024 -- Call for Papers (trendsfp.github.io) ## Important Dates Submission deadline: pre-symposium, full papers, Saturday 4 November, 2023 (AOE) Submission deadline: pre-symposium, draft papers, Friday 8 December, 2023 (AOE) Notification: pre-symposium full papers, Friday 8 December, 2023 Notification: pre-symposium draft papers, Thursday 14 December, 2023 Registration: Friday 5 January, 2024 TFPIE Workshop: Tuesday 9 January, 2024 TFP Symposium: Wednesday 10 - Friday 12 January, 2024 Submission deadline: post-symposium review, Friday 23 February, 2024 (AOE) Notification: post-symposium submissions, Friday 5 April, 2024 Camera-ready: post-symposium submissions, Friday 3 May, 2024 (AOE) 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. This year, TFP will take place in-person at Seton Hall University, in South Orange, NJ in the United States. It is co-located with the Trends in Functional Programming in Education (TFPIE) workshop, which will take on the day before the main symposium. Please be aware that TFP has several submission deadlines. The first, November 4, is for authors that wish to have their full paper reviewed prior to the symposium. Papers that are accepted in this way must also be presented at the symposium. The second, November 30, is for authors that wish to present their work or work-in progress at the symposium first without submitting to the full review process for publication. These authors can then take into account feedback received at the symposium and submit a full article for review by the third deadline, February 23. ## 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 2024 program chair, Jason Hemann. ## Best Paper Awards TFP awards two prizes for the best papers each year. First, to reward excellent contributions, TFP awards a prize for the best overall paper accepted for the post-conference formal proceedings. Second, each year TFP also awards a prize for the best student paper. 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 the paper's first authors, and a student would present the paper. In both cases, it is the PC of TFP that awards the prize. In case the best paper happens to be a student paper, then that paper will receive both prizes. ## Instructions to Authors Authors must submit papers to: https://easychair.org/conferences/?conf=tfp24 Authors of papers have the choice of having their contributions formally reviewed either before or after the Symposium. Further, pre-symposium submissions may either be full (earlier deadline) or draft papers (later deadline). ## Pre-symposium formal review Papers to be formally reviewed before the symposium should be submitted before the early deadline and will receive their reviews and notification of acceptance for both presentation and publication before the symposium. A paper that has been rejected for publication but accepted for presentation may be resubmitted for the post-symposium formal review. ## Post-symposium formal review Draft papers will receive minimal reviews and notification of acceptance for presentation at the symposium. 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. ## Paper categories Draft papers and papers submitted for formal review are submitted as 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. ## Format Papers must be written in English, and written using the LNCS style. For more information about formatting please consult the Springer LNCS Guidelines web site: https://www.springer.com/gp/computer-science/lncs/conference-proceedings-gu… ## Organizing Committee Jason Hemann PC Chair Seton Hall University, USA Stephen Chang Symposium Chair University of Massachusetts Boston, USA Shajina Anand Local Arrangements Seton Hall University, South Orange, USA Peter Achten Publicity Chair Radboud University Nijmegen, Netherlands

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ByteString and ByteString.Builder questions
by Zoran Bošnjak 30 Nov '23

30 Nov '23

Hi all, if I understand correctly, the ByteString.Builder is used to efficiently construct sequence of bytes from smaller parts. However, for inspecting data (take, head, index...), a plain ByteString is required. What if the byte sequence manipulation task requires both, for example: - receive ByteString from the network (e.g: Network.Socket.ByteString.recv :: ... -> IO ByteString) - inspect and manipulate data (pure function) - resend to the network (e.g: Network.Socket.ByteString.sendMany :: ... -> [ByteString] -> IO ()) ... where a pure data manipulation could be something like: - extract some segments out of the original sequence - create and add some segments of bytes - reorder - concatinate It is somewhat inconvenient to use 2 different types for the task, namely the ByteString and the Builder... where both represent a sequence of bytes. I have tryed to define a Bytes type where both representations are available: import qualified Data.ByteString as BS import qualified Data.ByteString.Lazy as Bsl import qualified Data.ByteString.Builder as Bld data Bytes = Bytes { toByteString :: ByteString , toBuilder :: Builder , length :: Int } instance Semigroup Bytes ... instance Monoid Bytes ... -- create fromByteString :: ByteString -> Bytes fromByteString bs = Bytes { toByteString = bs , toBuilder = Bld.byteString bs , length = BS.length bs } -- inspect function example head :: Bytes -> Word8 head = BS.head . toByteString -- prepare to send data over the network toChunks :: Bytes -> [ByteString] toChunks = Bsl.toChunks . Bld.toLazyByteString . toBuilder The fields of Bytes are non-strict, so the expectation was that lazy evaluation will suspend unnecessary calculations and to have efficient inspection (via ByteString part) and efficient concatination (via Builder part). I have performed some benchmarks (not sure if they are exactly to the point), but the results of Bytes are not so good: Inspect test using ByteString: OK (0.50s) 5.51 ms ± 342 μs using Bytes: OK (0.17s) 62.0 ms ± 3.0 ms Construct test using Builder: OK (0.21s) 5.29 ms ± 361 μs using Bytes: OK (0.17s) 21.3 ms ± 1.6 ms naive: OK (0.81s) 49.6 ms ± 4.1 ms Here is the full code: https://gist.github.com/zoranbosnjak/7887d843056f07bac6061d20970e1d6a My questions are: 0) Where does the big timing difference comming from? Thunks? 1) Is there any simple way (INLINE pragmas... or some other tricks) to get the performance back with the current implementation? 2) Would DList [ByteString] or any other type be any better over the ByteString.Builder in this case? 3) What would be the most efficient (and reasonable) implementation to support this kind of data processing (inspecting and concatination) in some uniform way? In other words: Is it worth to have uniformity here? 4) Is the Network.Socket.ByteString.sendMany function the way to go in cases where the byte sequence is constructed from segment or is there any better (faster) way? regards, Zoran

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Mutual scoping question
by Todd Wilson 28 Nov '23

28 Nov '23

Hello, Cafe: Is there a preferred way to define two top-level mutually recursive functions, f and g, that both use a common local function h such that h is (1) only defined once and (2) does not escape the scope of f and g? I suppose it could be done like this: fg = let f ... = ... f,g,h ... g ... = ... f,g,h ... h ... = ... h ... in (f,g) f = fst fg g = snd fg but is there something more elegant than this that I'm not seeing? Todd Wilson

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Re: [Haskell-cafe] [Haskell] ANT 2024 CFP (December 4, 2023 (extended)): The 15th International Conference on Ambient Systems, Networks and Technologies (ANT) , Hasselt, Belgium, April 23-25, 2024
by Jeremy Gibbons 27 Nov '23

27 Nov '23

I don’t know what Ivan’s relationship to the list is (for the record, I am not a list administrator myself, just a member of the community). But Ivan makes a good point. The three Haskell mailing lists have a specific purpose: "to discuss issues related to Haskell”. In the last year you appear to have posted 53 adverts for five conferences, called "Ambient Systems, Networks and Technologies", "Emerging Data and Industry", "Information and Communication Technologies in Healthcare", "Emerging Ubiquitous Systems and Pervasive Networks", "Sustainable Energy Information Technology", and "Mobile Systems and Pervasive Computing”. I don’t see that any of these are “related to Haskell”. Has there ever been any paper mentioning Haskell at any of these conferences? Do their calls for papers mention functional programming? If these conferences are not “related to Haskell”, then their announcements do not belong on the Haskell mailing list. Jeremy PS Diverting from the announcements list to haskell-cafe, the discussion list. > On 27 Nov 2023, at 07:28, Ali BENZERBADJ <ali.benzerbadj(a)univ-temouchent.edu.dz> wrote: > > Dear Ivan, > I would like to ask you to introduce yourself first, please. Are you the admin of the mailing list? I assume that Haskell is the one who assesses the relevance of announcements. If the topic doesn't interest you, just ignore it, and that's it. > > Yours sincerely. > > On Sun, 26 Nov 2023 at 23:07, Ivan Perez <ivanperezdominguez(a)gmail.com <mailto:ivanperezdominguez@gmail.com>> wrote: > Ali, > > None of the CfPs you've sent to this mailing list over the past year appear even remotely related to Haskell. I doubt people on this list will find them relevant or interesting. > > Could you please stop sending CfPs to haskell and haskell-cafe? > > Thanks > > Ivan > > On Sun, 26 Nov 2023 at 11:19, Ali BENZERBADJ <ali.benzerbadj(a)univ-temouchent.edu.dz <mailto:ali.benzerbadj@univ-temouchent.edu.dz>> wrote: > *************************************************************************** > The 15th International Conference on Ambient Systems, Networks and Technologies (ANT) > Hasselt, Belgium > April 23-25, 2024 > > *************************************************************************** > Conference Website: http://cs-conferences.acadiau.ca/ant-24/ <http://cs-conferences.acadiau.ca/ant-24/> > Workshops: http://cs-conferences.acadiau.ca/ant-24/#workshop <http://cs-conferences.acadiau.ca/ant-24/#workshop> > > Important Dates > - Workshops Proposals Due: October 20, 2023 > - Paper Submission Due: December 4, 2023 (extended) > - Acceptance Notification: January 15, 2024 > - Camera-Ready Submission: February 9, 2024 > > ANT 2024 accepted papers will be published by Elsevier Science in the open-access Procedia Computer Science series on-line. Procedia Computer Science is hosted by Elsevier on www.Elsevier.com <http://www.elsevier.com/> and on Elsevier content platform ScienceDirect (www.sciencedirect.com <http://www.sciencedirect.com/>), and will be freely available worldwide. All papers in Procedia will be indexed by Scopus (www.scopus.com <http://www.scopus.com/>) and by Thomson Reuters' Conference Proceeding Citation Index (http://thomsonreuters.com/conference-proceedings-citation-index/ <http://thomsonreuters.com/conference-proceedings-citation-index/>). All papers in Procedia will also be indexed by Scopus (www.scopus.com <http://www.scopus.com/>) and Engineering Village (Ei) (www.engineeringvillage.com <http://www.engineeringvillage.com/>). This includes EI Compendex (www.ei.org/compendex <http://www.ei.org/compendex>). Moreover, all accepted papers will be indexed in DBLP (http://dblp.uni-trier.de/ <http://dblp.uni-trier.de/>). The papers will contain linked references, XML versions and citable DOI numbers. You will be able to provide a hyperlink to all delegates and direct your conference website visitors to your proceedings. Selected papers will be invited for publication, in the special issues of: > > > - International Journal of Ambient Intelligence and Humanized Computing (IF: 4.594), by Springer (http://www.springer.com/engineering/journal/12652 <http://www.springer.com/engineering/journal/12652>) > - International Journal Personal and Ubiquitous Computing (IF:3.006), Springer (https://www.springer.com/journal/779 <https://www.springer.com/journal/779>) > - International Journal on Transportation Research Part A: Policy and Practice (IF: 3.992), by Elsevier (https://www.journals.elsevier.com/transportation-research-part-a-policy-and… <https://www.journals.elsevier.com/transportation-research-part-a-policy-and…>) > > > ANT 2024 will be held in Hasselt, Belgium. ANT 2024 is co-organized & co-hosted by the Hasselt University, Belgium. Since 1973 Hasselt University is located on the Campus Diepenbeek, which occupies an attractive 150 acre site in the middle of Limburg's green belt. It is 2 kms west of the town centre of Diepenbeek, a residential town of 17.717 inhabitants, and 4 kms east of Hasselt which has a population of about 69.529 and is the administrative and commercial centre of the province. Brussels is 90 kms away (to the South-West), Antwerp lies 90 kms to the West, Liège (in the French-speaking part of Belgium) 45 kms to the South, Maastricht (in the Netherlands) 25 kms to the East, Aachen (in Germany) 60 kms to the South-East. > > ANT 2024 will be held in conjunction with the 7th International Conference on Emerging Data and Industry (EDI40). > > Conference Tracks > - Agent Systems, Intelligent Computing and Applications > - Big Data and Analytics > - Cloud Computing > - Context-awareness and Multimodal Interfaces > - Emerging Networking, Tracking and Sensing Technologies > - Human Computer Interaction > - Internet of Things > - Mobile Networks, Protocols and Applications > - Modelling and Simulation in Transportation Sciences > - Multimedia and Social Computing > - Service Oriented Computing for Systems & Applications > - Smart, Sustainable Cities and Climate Change Management > - Smart Environments and Applications > - Systems Security and Privacy > - Systems Software Engineering > - Vehicular Networks and Applications > - General Track > > > General Chairs > > Atta Badii, University of Reading, UK > Albert Zomaya, The University of Sydney, Australia > > Program Chairs > > Hossam Hassanein, Queen's University, Canada > Ansar-Ul-Haque Yasar, Hasselt University, Belgium > > Workshops Chair > > Stephane Galland, UTBM, France > > Vice Chairs > > Muhammad Adnan, Hasselt University, Belgium > Manzoor Ahmed, Hubei Engineering University, Xiaogan, China > Akramul Azim, Ontario Tech University, Canada > Ayoub Bahnasse, Hassan II University, Morocco > Nik Bessis, Edge Hill University, UK > Samia Bouzefrane, CEDRIC Lab Conservatoire National des Arts et Metiers, France > Junsung Choi, Chungbuk National University, Republic of Korea > Robertas Damasevicius, Kaunas University of Technology, Lithuania > Antonella Galizia, Principal Scientist, CNR, Italy > Mohammad Ghanim, Ministry of Transport, Qatar > Stefano Guarino, IAC-CNR Rome, Italy > Faouzi Kammoun, Ecole Superieure Privee d'Ingenierie et de Technologies, Tunis > Bouabdellah Kechar, Oran 1 Ahmed BenBella University, Algeria > Ridha Khedri, McMaster University, Canada > Flavio Lombardi, Roma Tre University of Rome, Italy > Yazan Mualla, UTBM, France > Aneta Poniszewska-Maranda, Lodz University of Technology, Poland > Khair Eddin Sabri, The University of Jordan, Jordan > Cristina Seceleanu, Malardalen University, Sweden > Khaled Shaaban, Utah Valley University, USA > Kamran Siddique, Xiamen University Malaysia, Malaysia > Mohamed Tabaa, EMSI, Morocco > Igor Tchappi, University of Luxembourg, Luxembourg > > Technical Program Committee > > http://cs-conferences.acadiau.ca/ant-24/#programCommittees <http://cs-conferences.acadiau.ca/ant-24/#programCommittees> > > Publicity Chairs > > Ali Benzerbadj, University of Ain Temouchent Belhadj Bouchaib, Algeria > Wim Ectors, Hasselt University, Belgium > Siddardha Kaja, Air Canada, Canada > Orven E. Llantos, MSU-IIT, Philippines > Farhan Ullah, Northwestern Polytechnical University, China > > International Journals Chairs > > Haroon Malik, Marshall University, USA > Michael Sheng, Macquarie University, Australia > > Advisory Committee > > Reda Alhajj, University of Calgary, Canada > Sajal K. Das, The University of Texas at Arlington, USA > Erol Gelenbe, Imperial College, UK > Ibad Kureshi, Inlecomm Systems, Belgium > Vincenzo Loia, University of Salerno, Italy > Peter Sloot, Universiteit van Amsterdam, Netherlands > Ralf Steinmetz, Technische Universitaet Darmstadt, Germany > Katia Sycara, Carnegie Mellon University, USA > Peter Thomas, Manifesto Research, Australia > > International Liaison Chairs > > Soumaya Cherkaoui, Sherbrooke University, Canada > Paul Davidsson, Malmo University, Sweden > David Taniar, Monash University, Australia > > Steering Committee Chair and Founder of ANT > > Elhadi Shakshuki, Acadia University, Canada > > -- > Ali Benzerbadj > Lecturer, University of Ain Temouchent > Ain Temouchent, Algeria > Research Laboratory in Industrial Computing and Networks (RIIR) > Research team :"Networks and QoS" > University of Oran 1 Ahmed Ben Bella, Oran, Algeria > Mob(s): +213 6 61622162 > E-mail(s):.benzerbadj@univ-temouchent.edu.dz <mailto:ali.benzerbadj@univ-temouchent.edu.dz>, ali_benz(a)yahoo.fr <mailto:ali_benz@yahoo.fr>, > _______________________________________________ > Haskell mailing list > Haskell(a)haskell.org <mailto:Haskell@haskell.org> > http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell <http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell> > > > -- > Ali Benzerbadj > Lecturer, University of Ain Temouchent > Ain Temouchent, Algeria > Research Laboratory in Industrial Computing and Networks (RIIR) > Research team :"Networks and QoS" > University of Oran 1 Ahmed Ben Bella, Oran, Algeria > Mob(s): +213 6 61622162 > E-mail(s):.benzerbadj@univ-temouchent.edu.dz <mailto:ali.benzerbadj@univ-temouchent.edu.dz>, ali_benz(a)yahoo.fr <mailto:ali_benz@yahoo.fr>, > _______________________________________________ > Haskell mailing list > Haskell(a)haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell Jeremy.Gibbons(a)cs.ox.ac.uk Oxford University Department of Computer Science, Wolfson Building, Parks Road, Oxford OX1 3QD, UK. +44 1865 283521 http://www.cs.ox.ac.uk/people/jeremy.gibbons/

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Folded long string literals and CPP?
by Viktor Dukhovni 23 Nov '23

23 Nov '23

It looks like there's some sort of syntax conflict between CPP and long string literals folded across multiple lines. Is there a way to have both CPP and folded long string literals? $ cat /tmp/foo.hs {-# LANGUAGE CPP #-} module Main(main) where hello :: String hello = "Hello\ \ World!" main :: IO () main = print hello ---- $ ghci /tmp/foo.hs GHCi, version 9.8.1: https://www.haskell.org/ghc/ :? for help [1 of 2] Compiling Main ( /tmp/foo.hs, interpreted ) /tmp/foo.hs:5:25: error: [GHC-21231] lexical error in string/character literal at character 'W' | 5 | hello = "Hello\ | ^ Failed, no modules loaded. λ> Leaving GHCi. When I run the input through "cpp -E" I get: {-# LANGUAGE CPP #-} module Main(main) where hello :: String hello = "Hello \ World!" main :: IO () main = print hello Clearly not what I want, so the subsequent lexical error from GHC is not surprising, but is there a workaround that allows folding long strings across lines and retaining the layout. Given that the CPP lexer also recognises quoted strings, it looks like a difficult to reconcile mismatch. There would need be some other sort of joiner understood by GHC, where each string fragment is fully enclosed in quotes. Would the below be acceptable? {-# LANGUAGE CPP #-} module Main(main) where hello :: String hello = ##"Hello"\ ##"World!" main :: IO () main = print hello This is turned by CPP into either (version-dependent): {-# LANGUAGE CPP #-} module Main(main) where hello :: String hello = ##"Hello" ##"World!" main :: IO () main = print hello or: {-# LANGUAGE CPP #-} module Main(main) where hello :: String hello = ##"Hello" ##"World!" main :: IO () main = print hello which (or some suitable variant?) GHC could then also recognise as multiple fragments of the same single string literal? -- Viktor.

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Re: [Haskell-cafe] A question about type families conflicting instances
by Darryn 23 Nov '23

23 Nov '23

On Wednesday, 22 November 2023 10:30:01 PM ACDT haskell-cafe-request(a)haskell.org wrote: > > Thank you to anyone in advance who can help; I do really appreciate it. > > I think a simple redefinition of "Formable" takes care of the described > obstacle. Do you have other requirements that make it impractical? > > -- > Viktor. > Hi Viktor. Thanks again for taking a look at this and giving me advice. I hadn't thought of the problem like this, using kind representation. The short answer is that I'm not sure yet whether there are any other requirements that bear on this, given the exploratory nature of the little project, but having just played with your modifications and then worked it back to the main code, this solution looks excellent at this stage. Really appreciate it. Regards, D.

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