January 2023 - Haskell-Cafe

Surprising interaction between @-patterns and nested patterns
by Tom Ellis 05 Jan '23

05 Jan '23

Consider the following: let x0 = (undefined, ()) ; ((_, _), _) = x0 in x0 `seq` () () but then combining the patterns into an @-pattern, which really feels like it shouldn't change semantics: let x1@((_, _), _) = (undefined, ()) in x1 `seq` () -> undefined Does this strike anyone else as odd? The reason for this behaviour is that let x@p = rhs in body is translated to case rhs of ~(x@p) -> body according to section 3.12 of The Report[1] which is then translated to (\x -> body) (case rhs of x@p -> x) if p binds no variables, according to section 3.17.3 of The Report[2], and then to (\x -> body) (case rhs of p -> (\x -> x) rhs) which is equivalent to (\x -> body) (case rhs of p -> rhs) Putting it all together let x0 = (undefined, ()) ; ((_, _), _) = x0 in x0 `seq` () desugars as (\x0 -> x0 `seq` ()) (let v = (undefined, ()) in case v of ((_, _), _) -> v) which evaluates as let v = (undefined, ()) in case v of ((_, _), _) -> () This seems very odd to me. Why should combining two non-diverging patterns into an @-pattern cause divergence? Specifically, the translation from let x@p = rhs in body to case rhs of ~(x@p) -> body seems highly dubious. It comes from the more general rule translating let p = rhs in body to case rhs of ~p in body but it seems to interact badly with @-patterns. It seems like the rule for @-patterns should be something like let x@p = rhs in body translates to case rhs of ~(x@(~p)) in body Then the original expression containing x1 would not diverge. Does anyone else have a view on this matter? Tom [1] https://www.haskell.org/onlinereport/exps.html#sect3.12 [2] https://www.haskell.org/onlinereport/exps.html#sect3.17.3

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CLC Election January 2023
by Andrew Lelechenko 05 Jan '23

05 Jan '23

The terms of three CLC members are ending in January, so we are seeking new nominations! # Who should apply? Anyone who meets the following criteria should apply: * Candidates should have enough bandwidth to review merge requests to `base` on a semi-frequent basis (3 to 5 per month), and sustain this for their 3 years term in a healthy manner. * Candidates should be able to contribute opinions and analysis to issues raised by the community as a part of the CLC proposal process on a semi-frequent basis (3 to 5 per month). * Candidates should be good communicators, and at least be able to articulate to the CLC team when they will be available vs. unavailable. * Candidates should be productive, and be able to follow through on merge requests and conversations to their completion in a diligent and timely manner. We encourage any and all who satisfy these requirements to apply. Please note that we are not looking for the biggest galaxy brain in the room - quite the opposite. We are looking for productive, motivated individuals who want to help support the ecosystem that we love. As such, we hope to build a broad sample of the community. # How can I apply? To apply for one of these positions, send an email to clc.nominations.2023(a)gmail.com that consists of the following data: * The header “CLC Election January 2023 - {your name}”. * Why you think you’re a good fit given the above criteria. * If applicable, please point us to some code you’ve written. Please apply before Feb 1. Best regards, Andrew

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[TFP 2023 Call For Participation] 24th International Symposium on Trends in Functional Programming
by Peter Achten 02 Jan '23

02 Jan '23

# TFP 2023 -- Call For Participation (trendsfp.github.io) ## Dates Registration: Friday 6th January, 2023 TFPIE Workshop: Thursday 12th January, 2023 TFP Symposium: Friday 13th - Sunday 15th January, 2023 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 UMass Boston, Massachusetts 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. ## 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 2023 program chair, Stephen Chang. ## 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, a prize for the best student paper is awarded each year. TFP traditionally pays special attention to research students, acknowledging that students are almost by definition part of new subject trends. A student paper is one for which the authors state that the paper is mainly the work of students, the students are listed as first authors, and a student would present the paper. 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 Papers must be submitted at: <https://easychair.org/conferences/?conf=tfp23> 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 web site. ## Program Committee Peter Achten, Radboud University Nijmegen, Netherlands Nada Amin, Harvard University, USA Ambrose Bonnaire-Sergeant, Untypable LLC, USA Laura M. Castro, University of A Coruña, Spain Stephen Chang (Chair), University of Massachusetts Boston, US John Clements, Cal Poly, USA Youyou Cong, Tokyo Institute of Technology, Japan Paul Downen, University of Massachusetts Lowell, USA Kathy Gray, Meta Platforms, Inc., UK Ben Greenman, University of Utah, USA Jason Hemann, Seton Hall University, USA Patricia Johann, Appalachian State University, USA Alexis King, Tweag, USA Julia Lawall, Inria-Paris, France Barak Pearlmutter, Maynooth University, Ireland Norman Ramsey, Tufts University, USA Ilya Sergey, National University of Singapore, Singapore Melinda Tóth, Eötvös Loránd University, Hungary Ningning Xie, University of Toronto, Canada

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