- Haskell-Cafe - Haskell.org

[ANN] cabal-clean (new tool)
by Andreas Abel 19 Aug '22

19 Aug '22

=== Wondering where your disk space goes with too many Haskell projects compiled with too many GHC versions? === https://hackage.haskell.org/package/cabal-clean https://github.com/andreasabel/cabal-clean `cabal-clean` is a small executable that removes outdated cabal build artifacts from `dist-newstyle`. A build tree is considered outdated if there is one with either - a newer version of the package you are building, or - a newer minor version of the GHC compiler. In contrast to `cabal clean`, the tool `cabal-clean` retains the latest build trees for each GHC major version. Thus, it is geared towards multi-GHC development. Example: (self-applied to cabal-clean's build directory) --- 3.7M ghc-8.8.4 /cabal-clean-0.1.20210815 --- 3.5M ghc-8.10.6/cabal-clean-0.1.20210815 --- 3.7M ghc-9.0.1 /cabal-clean-0.1.20210815 --- 3.5M ghc-8.10.6/cabal-clean-0.1.20210924 +++ 3.6M ghc-8.10.7/cabal-clean-0.1.20210924 +++ 3.7M ghc-9.0.1 /cabal-clean-0.1.20210924 The directories prefixed with --- will be deleted, the ones with +++ retained. Disclaimers: 1. cabal-clean does not check whether deletion will cause dangling references like broken symlinks etc. (Could happen if you created a symlink to an executable that resides in one of the deleted build directories.) 2. cabal-clean does not read nor utilize information from the .cabal file. 3. Calls `du` ("disk usage"), so, might not work on Windows. Enjoy, Andreas

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Ambiguous type variable with lenses
by Henry Laxen 18 Aug '22

18 Aug '22

-- run this with: ghci -package microlens-platform T7.hs {-# LANGUAGE TemplateHaskell #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE AllowAmbiguousTypes #-} {-# LANGUAGE FlexibleInstances #-} module T7 where import Lens.Micro.Platform type Lenstype f a b = (b -> f b) -> a -> f a data A = A { _a1 :: Int , _a2 :: String} deriving (Show) $(makeLenses ''A) class B a where lensB1 :: (Functor f) => Lenstype f a Int lensB2 :: (Functor f) => Lenstype f a String instance B A where lensB1 = a1 lensB2 = a2 xa = A 1 "one" ya1 = xa ^. a1 ya2 = xa ^. lensB1 test1 = ya1 == ya2 -- True -- But I would like to use a type variable for the String field of A data C b = C { _c1 :: Int , _c2 :: b} deriving (Show) $(makeLenses ''C) -- So next I define: class D a b where -- Need MultiParamTypeClasses here lensD1 :: (Functor f) => Lenstype f a Int -- Need AllowAmbiguousTypes here lensD2 :: (Functor f) => Lenstype f a b instance D (C b) b where -- Need FlexibleInstances here lensD1 = c1 lensD2 = c2 xc1 = C 1 "one" :: C String xc2 = C 1 'o' :: C Char yc1 = xc1 ^. c1 :: Int yc2 = xc2 ^. c1 :: Int test2 = yc1 == yc2 -- True -- All good until here. Now the trouble begins. If you uncomment the next two lines you get: -- zc1 = xc1 ^. lensD1 :: Int -- zc2 = xc2 ^. lensD1 :: Int -- T7.hs:62:14-19: error: -- • Ambiguous type variable ‘b1’ arising from a use of ‘lensD1’ -- prevents the constraint ‘(D (C String) b1)’ from being solved. -- Probable fix: use a type annotation to specify what ‘b1’ should be. -- These potential instance exist: -- instance D (C b) b -- -- Defined at /home/henry/haskell/dev/T7.hs:44:10 -- • In the second argument of ‘(^.)’, namely ‘lensD1’ -- In the expression: xc1 ^. lensD1 :: Int -- In an equation for ‘zc1’: zc1 = xc1 ^. lensD1 :: Int -- | -- 62 | zc1 = xc1 ^. lensD1 :: Int -- | ^^^^^^ -- T7.hs:63:14-19: error: -- • Ambiguous type variable ‘b0’ arising from a use of ‘lensD1’ -- prevents the constraint ‘(D (C Char) b0)’ from being solved. -- Probable fix: use a type annotation to specify what ‘b0’ should be. -- These potential instance exist: -- instance D (C b) b -- -- Defined at /home/henry/haskell/dev/T7.hs:44:10 -- • In the second argument of ‘(^.)’, namely ‘lensD1’ -- In the expression: xc2 ^. lensD1 :: Int -- In an equation for ‘zc2’: zc2 = xc2 ^. lensD1 :: Int -- | -- 63 | zc2 = xc2 ^. lensD1 :: Int -- | ^^^^^^ -- But zc1 and zc2 don't care what is in the second slot. I would -- like to store different types in the second slot of C, but the -- first slot of C will always be an Int. Is there any way to -- manipulate the first slot alone? I got some compiler "suggestions" -- concernting RankNTypes and QuantifiedConstraints but nothing I -- tried ended up working. -- Thanks in advance for your help. -- Henry Laxen

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Web server with dynamic data
by Hans Georg Schaathun 16 Aug '22

16 Aug '22

Hi, I have been fiddling with this idea for some time, and I wonder if this may be the right place to ask a rather probing question!? It has been some years since my last visit to the list. I have been searching for examples using functional reactive programming to make web servers, but this proves surprisingly hard to find. I found the netwire library, but given that the last update was 2011 I am not sure I want to risk that ... So maybe I was asking the wrong question. I have a rather complex system of RDF Graphs (using Swish), with reasoners making derived graphs, and updates being made only on the original graphs. There are multiple constituent graphs to avoid having to recompute everything upon update. Now I was thinking that this looks like a typical case for FRP, with each graph a Behaviour, recomputing derived graph only when the source behaviour changes. I am not sure if I am right. Any opinions? The second part of this is the web server to allow queries (read and update) to the RDF Graphs. The first prototype uses Scotty with STM for storage, but when I add more constituent graphs, I really do not want an update to block access to other constituent graphs, which is what I thought I could avoid in an FRP model. Without much experience writing interactive stuff in Haskell, I cannot figure out how to wire the interaction between Scotty and either netwire or banana which are the two FRP libraries I have tried to comprehend. Are there any examples out there to look at? I am not really committed to any library or paradigm, except for RDF and Swish, so any ideas will be welcome, even pointing me away from everything I thought I needed ... Thanks for reading, :-- George

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IFL22: Early registration deadline August 15th
by Pieter Koopman 15 Aug '22

15 Aug '22

*IFL 2022Frederiksberg Campus of Faculty of Science, UCPH, CopenhagenAugust 31s-September 2nd, 2022* *Early registration deadline: August 15th AoE * *See **https://ifl22.github.io/* <https://ifl22.github.io/>* for more information.* *CALL FOR PARTICIPATION:* The 34th Symposium on Implementation and Application of Functional Languages (IFL 2022) Copenhagen, August 31st-September 2nd, 2022 *Important dates* Submission deadline of draft papers August 8th, 2022 (EXPIRED) Notification of acceptance August 9th, 2022 (EXPIRED) Early registration deadline August 15th, 2022 (AoE) Late registration deadline August 31st, 2022, 12:59 CET (UTC+2) IFL Symposium August 31st - September 2nd, 2022 (We-Fr) *Scope* The goal of IFL is to bring together researchers and developers actively engaged in the implementation and application of functional programming languages and function-oriented programming. IFL 2022 is held in beautiful Copenhagen, Denmark and is a venue for researchers to present and discuss new ideas and concepts, work in progress, and publication-ripe results related to the implementation and application of functional programming languages and function-oriented programming. *Invited speakers* IFL 2022 is pleased to announce keynote talks by the following three invited speakers: * Peter Sestoft, Professor, Head of Department, IT University of Copenhagen, Denmark: "Abstract machines and functional language implementation" * Lennart Augustsson, Principal Programmer, Epic Games: "Verse - a new functional-logic language" * Thomas Gazagnaire, Chief Technology Officer and co-founder, Tarides: "Talk title to be announced" *Venue and registration* The symposium will be held physically on the Frederiksberg Campus of the Faculty of Science at the University of Copenhagen. Days 1 and 2 (August 31st and September 1st) will be in meeting room A2-84.01 at Thorvaldsensvej 40. Day 3 (September 2nd) will be in the Celebration Auditorium at Bülowsvej 17. For registration and fees, please consult the symposium web site at https://ifl22.github.io/. Please notice that the early registration date is August 15, 2022 (AoE). *Accepted papers* * Asynchronous Shared Data Sources. Mart Lubbers, Haye Böhm, Pieter Koopman and Rinus Plasmeijer. * Heuristics-based Type Error Diagnosis for Haskell: the case of type families. Niels Kwadijk and Jurriaan Hage. * Verified Technology Mapping in an Agda DSL for Circuit Design. João Paulo Pizani Flor and Wouter Swierstra. * Creating Interactive Visualizations of TopHat Programs. Mark Gerarts, Marc de Hoog, Nico Naus and Tim Steenvoorden. * An SQL Frontend on top of OCaml for Data Analysis. Yan Dong, Yahui Song and Wei-Ngan Chin. * A Structure Editor with Type-Safe Copy/Paste. Hans Hüttel, Christoffer Lind Andersen, Nana Gjerulf Sandberg, Anja Elisasen Lumholtz Nielsen and Peter Mikkelsen. * How to fold and color a map: Comparing Use-Cases of Tree-Fold vs Fold-Left. Jim Newton. * Compiling a functional array language with non-semantic memory information. Philip Munksgaard, Cosmin Oancea and Troels Henriksen. * Systems of partial values and their applications in Haskell. Natasha England-Elbro. * First-Class Data Types in Shallow Embedded Domain-Specific Languages using Metaprogramming. Mart Lubbers, Pieter Koopman and Rinus Plasmeijer. * Set-theoretic Types for Erlang. Albert Schimpf, Stefan Wehr and Annette Bieniusa. * Strongly-Typed Multi-View Stack-Based Computations. Pieter Koopman and Mart Lubbers. * Ztrategic: Strategic Programming with Zippers. José Nuno Macedo, Emanuel Rodrigues, Marcos Viera and João Saraiva. * Higher-ranked region inference for polymorphic, lazy languages. Ivo Gabe de Wolff and Jurriaan Hage. * Jeopardy: An invertible functional programming language. Joachim Kristensen, Robin Kaarsgaard and Michael Kirkedal Thomsen. * The Foil: Capture-Avoiding Substitution With No Sharp Edges. Dougal Maclaurin, Alexey Radul and Adam Paszke. * Verified Causal Broadcast with Liquid Haskell. Patrick Redmond, Gan Shen, Niki Vazou and Lindsey Kuper. * Towards Inversion of Tail-recursive Term Rewriting Systems. Maria Bendix Mikkelsen, Robert Glück and Maja Hanne Kirkeby. * A Confluence and Termination Checker for Haskell Rewrite Rules. Makoto Hamana. * On Generating Out-Of-Core GPU Code for Multi-Dimensional Array Operations. Patrick van Beurden and Sven-Bodo Scholz. * Compiling Haskell for Energy Efficiency: Analysis of Individual Transformations. Bernardo Santos, João Fernandes, Maja Kirkeby and Alberto Pardo. *Post-symposium peer review * Following IFL tradition, IFL 2022 will use a post-symposium review process to produce the formal proceedings. Before the symposium authors submit draft papers. These draft papers have been screened by the program chair to make sure that they are within the scope of IFL. The draft papers will be made available to all participants at the symposium. Each draft paper is presented by one of the authors at the symposium. Notice that it is a requirement that draft papers that are accepted for presentation be presented physically at the symposium. After the symposium the authors are invited to submit a full paper, incorporating feedback from discussions at the symposium. Work submitted to IFL may not be simultaneously submitted to other venues; submissions must adhere to ACM SIGPLAN's republication policy. The program committee will evaluate these submissions according to their correctness, novelty, originality, relevance, significance, and clarity, and will thereby determine whether the paper will be accepted or rejected for the formal proceedings. Papers that are accepted for the formal proceedings are published in the International Conference Proceedings Series of the ACM Digital Library, as in previous years. *Peter Landin Prize* The Peter Landin Prize is awarded to the best paper presented at the symposium every year. The honored article is selected by the program committee based on the submissions received for the formal review process. The prize carries a cash award equivalent to 150 Euros. *Sponsors* IFL 2022 is financially supported by - Meta (Silver sponsor), - Well-typed (Bronze sponsor), - Funktionelle Københavnere (Bronze sponsor), and - University of Copenhagen (administrative support, host). *Organisation* General chair Fritz Henglein, University of Copenhagen Program chair Martin Elsman, University of Copenhagen Communications chair Troels Henriksen, University of Copenhagen *Program committee* Laura M. Castro Universidade da Coruña, Spain David Christiansen Haskell Foundation Martin Elsman University of Copenhagen, Denmark (chair) Matthew Fluet Rochester Institute of Technology, USA Clemens Grelck Universiteit van Amsterdam, The Netherlands Zhenjiang Hu Peking University, China Robin Kaarsgaard University of Edinburgh, Scotland Gabriele Keller Utrecht University, The Netherlands Oleg Kiselyov Tohoku University, Japan Neil Mitchell Facebook Stefan Monnier Universite de Montreal, Canada Magnus Myreen Chalmers University, Sweden Cyrus Omar University of Michigan, USA Romain Péchoux University of Lorraine, Inria, France Rinus Plasmeijer Radboud University, The Netherlands Morten Rhiger Roskilde University, Denmark Peter van Roy Catholic University of Louvain, Belgium Olin Shivers Northeastern University, USA Peter Thiemann University of Freiburg, Germany Marcos Viera Universidad de la República, Uruguay Meng Wang University of Bristol, UK [image: beacon]

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Re: [Haskell-cafe] Haskell SQL backends: How is data handed over?
by Olaf Klinke 12 Aug '22

12 Aug '22

Anthony Clayden wrote: > What is your evidence that number/String is a concern here? It's all > happening in-memory. > > Whereas sending whatever to SQL then needs putting it to disk, which is > orders-of-magnitude slower. (Or is this an in-memory database?) > > This thread has already devoted more cycles to speculation than you're > going to reclaim through number formatting, methinks. Very good point. I'm fairly new to SQL, have a solution that works and started to wonder how efficient it is. Since the way data is passed to and from the DB engine affects every database interaction, for every user, I thought it might be worthwile investigating. And as I said earlier, profiling other code has proved that number parsing can make up a significant portion of a data-heavy program's CPU time. Thus it's not speculation entirely. Olaf

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Re: [Haskell-cafe] Haskell SQL backends: How is data handed over?
by Anthony Clayden 12 Aug '22

12 Aug '22

> the backend constructs a complete SQL query statement in form of a string (including the SqlValues), and hands that to the database driver to parse. Is that indeed so? > Hi Olaf, that's the usual format for any HLL to pass statements (queries or updates) to SQL. Most HLLs provide some sort of modulate/demodulate so your program doesn't see the raw numbers-as-strings, but the parsing is going on in the background. Going via CSV isn't really saving anything: the "bulk insert" is again parsing those commas and the bits in between. (A dedicated SQL engine is probably more efficient than Haskell's string handling.) AntC

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Re: [Haskell-cafe] Haskell SQL backends: How is data handed over?
by Anthony Clayden 12 Aug '22

12 Aug '22

> @Olaf You mean that formatting a Scientific number as String is more efficient > than formatting an Integer/Double in its usual representation? > How about parsing? I'm not going to defend the 'efficiency' of Haskell's String formatting/parsing, but ... What is your evidence that number/String is a concern here? It's all happening in-memory. Whereas sending whatever to SQL then needs putting it to disk, which is orders-of-magnitude slower. (Or is this an in-memory database?) This thread has already devoted more cycles to speculation than you're going to reclaim through number formatting, methinks.

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Just released: cabal 3.8.1.0
by Artem Pelenitsyn 12 Aug '22

12 Aug '22

---------- Forwarded message --------- From: Mikolaj Konarski <mikolaj(a)well-typed.com> Date: Thu, Aug 11, 2022 at 7:05 PM Subject: Just released: cabal 3.8.1.0 To: <cabal-devel(a)haskell.org> Here's the happy news. :) Let me copy below the contents of the announcement from https://discourse.haskell.org/t/just-released-cabal-3-8-1-0/4920 but, additionally, on this mailing list I'd like to personally thank Emily and Oleg who, among all the giants on whose shoulders we stand, have most directly affected 3.8.1.0 with their hearts and wisdom. Haskell community owes you big time. --- I’m proud to announce 3.8.1.0 version of Cabal the library and cabal-install the tool. It’s the fruit of concerted effort of innumerous collaborators, from users, through developers, to mentors, caretakers and administrators of our linked community and infrastructure sections. You, people, rock. This version works with the just released GHC 9.4.1 (in fact, for Windows it’s probably necessary) and is already available form GHCup and other channels. More technical details, APIs, changelogs and regressions can be found at Release cabal v3.8.1.0 · haskell/cabal · GitHub. The release is huge, so let me mention only a few random highlights: public/private sublibraries are fully supported and no longer experimental (6. Package Description — Cabal 3.8.1.0 User's Guide) you can now put in your cabal.project something like import: https://www.stackage.org/lts-18.5/cabal.config and it works (7. cabal.project Reference — Cabal 3.8.1.0 User's Guide) new Cabal-syntax and cabal-install-solver packages have been split off there’s no more confusion of compiler options for the local code and for the dependencies (https://github.com/haskell/cabal/pull/7973) one can now define code generators in test stanzas, which is one more principled step away from Custom Setups (https://github.com/haskell/cabal/pull/7688) Cabal badly needs your feedback and your contributions. Please keep them coming. _______________________________________________ cabal-devel mailing list cabal-devel(a)haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/cabal-devel

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Re: [Haskell-cafe] Haskell SQL backends: How is data handed over?
by Olaf Klinke 11 Aug '22

11 Aug '22

> My observation about the "scientific" package is also relevant here: > most DBMSes have a different notion of "number" than most programming > languages, so unless there is specifically a binary number field type > it is probably necessary to send it as a string of some variety. The > "scientific" package abstracts over this for Haskell. You mean that formatting a Scientific number as String is more efficient than formatting an Integer/Double in its usual representation? How about parsing? In most parsing libraries I've seen [1,2,3] the following code transforms a string of digits to an integer. import Data.Char (ord) import Data.Foldable (foldl') -- The parser ensures only digit Chars -- are passed to this function. fromDigit :: Num a => Char -> a fromDigit = let z = ord '0' in \digit -> fromIntegral (ord digit - z) appendDigit :: Num a => a -> Char -> a appendDigit x d = 10 * x + fromDigit d digitsToNum :: Num a => [Char] -> a digitsToNum = foldl' appendDigit 0 If in addition to 'show' the function prependDigit (and its foldr cousin for digits behind the floating point) were particularly efficient for Scientific [*], that would indeed make a strong case for using Scientific in parsing and (SQL-)database applications. Olaf [1] https://hackage.haskell.org/package/parsec-3.1.15.1/docs/src/Text.Parsec.To… [2] https://hackage.haskell.org/package/megaparsec-9.2.1/docs/src/Text.Megapars… [3] https://hackage.haskell.org/package/attoparsec-0.14.4/docs/src/Data.Attopar… [*] This seems not to be the case currently: The Num instance is implemented as Scientific c1 e1 * Scientific c2 e2 = Scientific (c1 * c2) (e1 + e2) Would it be a bad idea to add special cases for numbers of the form Scientific 1 e? It penalizes all multiplications with a pattern match.

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Re: [Haskell-cafe] Haskell SQL backends: How is data handed over?
by Olaf Klinke 10 Aug '22

10 Aug '22

Thanks all for the replies. It seems in my specific setup values are indeed passed as strings, see below. Oliver Charles wrote: > I can't speak for SQL in general, but if you're targeting PostgreSQL note that the hasql library uses a binary wire format. Good to know, thanks. It might be that for my specific case the database choice ship has sailed, unfortunately. Anthony Clayden wrote: > Going via CSV isn't really saving anything: the "bulk insert" is again > parsing those commas and the bits in between. (A dedicated SQL engine is > probably more efficient than Haskell's string handling.) That was what I was thinking, too: The bulk insert must also parse the numbers, so it would be kind of a waste to have Haskell parse the numbers, format them as Strings in the CSV just to have the SQL server parse them again. Brandon Allbery wrote: > More specifically, a query or DML statement is a string with ? > placeholders for values, which is "prepare"d to turn it into internal > format and then executed one or more times with values supplied. Sending the SQL statement as string is probably fine. I guess it depends on the specific HDBC backend whether run :: Connection -> String -> [SqlValue] -> IO Integer also sends the SqlValue arguments as String. Specifically, I chose persistent with HDBC-odbc backend because (1) We're talking to a Microsoft SQL server from a Linux client via unixODBC, (2) We chose Microsoft SQL to ensure trouble-free integration into the Microsoft office world, (3) I expect a web application will emerge from this, hence persistent because it integrates well with Yesod. In [HDBC-odbc] it is implemented in sqlBindValue, sqlBindParameter which contains CString -- ^ Parameter value pointer The actual value (if not a string) is converted to ByteString (using the Convertible class) and placed into the CString, it seems. The Convertible SqlValue Bytestring instance uses fromString and Convertible SqlValue String which in turn uses show [HDBC]. So yep, to ODBC the SqlValues are passed as Strings. HDBC-sqlite3 does the same. I opened [1]. Olaf [HDBC-odbc] https://hackage.haskell.org/package/HDBC-odbc-2.5.0.1/docs/src/Database-HDB… [HDBC] https://hackage.haskell.org/package/HDBC-2.4.0.4/docs/src/Database.HDBC.Sql… [1] https://github.com/hdbc/hdbc/issues/56

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Haskell SQL backends: How is data handed over?
by Olaf Klinke 10 Aug '22

10 Aug '22

Dear Café, I was discussing with a friend the fastest way to shovel data into a SQL database after parsing the raw (textual) data with Haskell. I am concerned about numeric conversion: In my experience parsing the file structure is fast. The majority of the time is spent converting strings of digits to numbers. I hoped that once Haskell has constructed a Double, the backend driver can hand that binary value over to the database engine. But Database.HDBC.Statement has a field orginalQuery :: String and HDBC has functions prepare :: Connection -> String -> IO Statement run :: Connection -> String -> [SqlValue] -> IO Integer which makes me wonder whether the backend constructs a complete SQL query statement in form of a string (including the SqlValues), and hands that to the database driver to parse. Is that indeed so? If yes, the numbers should never be parsed in the first place: The DB will do that anyways. I might as well construct a new CSV file and let the database do a bulk insert on that. The above is specific to the HDBC backend. If there are other backends/frameworks that do the marshalling more efficiently, please let me know. Thanks Olaf

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Re: [Haskell-cafe] ghc doesn't work after installing 9.4.1 on my Mac
by Shayne Fletcher 10 Aug '22

10 Aug '22

Known issue George. See e.g. https://gitlab.haskell.org/ghc/ghc/-/issues/21985 On Tue, Aug 9, 2022, 4:33 PM George Colpitts <george.colpitts(a)gmail.com> wrote: > Unfortunately ghc doesn't work after installing 9.4.1 on my Mac. Does it > work for others? > > After the install finishes when I do the following: > > $ ghc --version > bash: /usr/local/bin/ghc: Permission denied > $ sudo chmod +x /usr/local/bin/ghc > $ghc --version > /usr/local/bin/ghc: line 1: exec: : not found > $ cat /usr/local/bin/ghc > exec "$executablename" -B"$libdir" ${1+"$@"} > $ cat /usr/local/bin/ghc-9.4.1 > #!/bin/sh > exedir="/usr/local/lib/ghc-9.4.1/bin" > exeprog="ghc-9.4.1" > executablename="/usr/local/lib/ghc-9.4.1/bin/ghc-9.4.1" > bindir="/usr/local/bin" > libdir="/usr/local/lib/ghc-9.4.1/lib" > docdir="/usr/local/share/doc/ghc-9.4.1" > includedir="/usr/local/include" > > exec "$executablename" -B"$libdir" ${1+"$@"} > > > Thanks > George > > > > On Sun, Aug 7, 2022 at 6:30 PM Ben Gamari <ben(a)well-typed.com> wrote: > >> The GHC developers are very pleased to announce the availability of GHC >> 9.4.1. Binary distributions, source distributions, and documentation are >> available at downloads.haskell.org: >> >> https://downloads.haskell.org/ghc/9.4.1 >> >> This release includes: >> >> - A new profiling mode, `-fprof-late`, which adds automatic cost-center >> annotations to all top-level functions *after* Core optimisation has >> run. This provides informative profiles while interfering >> significantly less with GHC's aggressive optimisations, making it >> easier to understand the performance of programs which depend upon >> simplification.. >> >> - A variety of plugin improvements including the introduction of a new >> plugin type, *defaulting plugins*, and the ability for typechecking >> plugins to rewrite type-families. >> >> - An improved constructed product result analysis, allowing unboxing of >> nested structures, and a new boxity analysis, leading to less reboxing. >> >> - Introduction of a tag-check elision optimisation, bringing >> significant performance improvements in strict programs. >> >> - Generalisation of a variety of primitive types to be levity >> polymorphic. Consequently, the `ArrayArray#` type can at long last be >> retired, replaced by standard `Array#`. >> >> - Introduction of the `\cases` syntax from [GHC proposal 0302]. >> >> - A complete overhaul of GHC's Windows support. This includes a >> migration to a fully Clang-based C toolchain, a deep refactoring of >> the linker, and many fixes in WinIO. >> >> - Support for multiple home packages, significantly improving support >> in IDEs and other tools for multi-package projects. >> >> - A refactoring of GHC's error message infrastructure, allowing GHC to >> provide diagnostic information to downstream consumers as structured >> data, greatly easing IDE support. >> >> - Significant compile-time improvements to runtime and memory >> consumption. >> >> - On overhaul of our packaging infrastructure, allowing full >> traceability of release artifacts and more reliable binary >> distributions. >> >> - Reintroduction of deep subsumption (which was previously dropped with >> the >> *simplified subsumption* change) as a language extension. >> >> - ... and much more. See the [release notes] for a full accounting. >> >> Note that, as 9.4.1 is the first release for which the released artifacts >> will >> all be generated by our Hadrian build system, it is possible that there >> will be >> packaging issues. If you enounter trouble while using a binary >> distribution, >> please open a [ticket]. Likewise, if you are a downstream packager, do >> consider >> migrating to [Hadrian] to run your build; the Hadrian build system can be >> built >> using `cabal-install`, `stack`, or the in-tree [bootstrap script]. See >> the accompanying >> [blog post] for details on migrating packaging to Hadrian. >> >> We would like to thank Microsoft Azure, GitHub, IOG, the Zw3rk stake pool, >> Well-Typed, Tweag I/O, Serokell, Equinix, SimSpace, Haskell Foundation, >> and >> other anonymous contributors whose on-going financial and in-kind support >> has >> facilitated GHC maintenance and release management over the years. >> Finally, >> this release would not have been possible without the hundreds of >> open-source >> contributors whose work comprise this release. >> >> As always, do give this release a try and open a [ticket] if you see >> anything amiss. >> >> Happy testing, >> >> - Ben >> >> >> [GHC proposal 0302]: >> https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0302-c… >> [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new >> [bootstrap script]: >> https://gitlab.haskell.org/ghc/ghc/-/blob/e2520df3fffa0cf22fb19c5fb872832d1… >> [Hadrian]: >> https://gitlab.haskell.org/ghc/ghc/-/blob/e2520df3fffa0cf22fb19c5fb872832d1… >> [release notes]: >> https://downloads.haskell.org/~ghc/9.4.1/docs/users_guide/9.4.1-notes.html >> [blog post]: >> https://www.haskell.org/ghc/blog/20220805-make-to-hadrian.html >> _______________________________________________ >> ghc-devs mailing list >> ghc-devs(a)haskell.org >> http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs >> > _______________________________________________ > ghc-devs mailing list > ghc-devs(a)haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs >

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[ANNOUNCE] GHC 9.4.1-rc1 is now available
by Ben Gamari 08 Aug '22

08 Aug '22

The GHC developers are happy to announce the availability of the first (and likely last) release candidate of GHC 9.4.1. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org] This major release will include: - A new profiling mode, `-fprof-late`, which adds automatic cost-center annotations to all top-level functions *after* Core optimisation has run. This provides informative profiles while interfering significantly less with GHC's aggressive optimisations, making it easier to understand the performance of programs which depend upon simplification.. - A variety of plugin improvements including the introduction of a new plugin type, *defaulting plugins*, and the ability for typechecking plugins to rewrite type-families. - An improved constructed product result analysis, allowing unboxing of nested structures, and a new boxity analysis, leading to less reboxing. - Introduction of a tag-check elision optimisation, bringing significant performance improvements in strict programs. - Generalisation of a variety of primitive types to be levity polymorphic. Consequently, the `ArrayArray#` type can at long last be retired, replaced by standard `Array#`. - Introduction of the `\cases` syntax from [GHC proposal 0302] - A complete overhaul of GHC's Windows support. This includes a migration to a fully Clang-based C toolchain, a deep refactoring of the linker, and many fixes in WinIO. - Support for multiple home packages, significantly improving support in IDEs and other tools for multi-package projects. - A refactoring of GHC's error message infrastructure, allowing GHC to provide diagnostic information to downstream consumers as structured data, greatly easing IDE support. - Significant compile-time improvements to runtime and memory consumption. - On overhaul of our packaging infrastructure, allowing full traceability of release artifacts and more reliable binary distributions. - Reintroduction of deep subsumption (which was previously dropped with the *simplified subsumption* change) as a language extension. - ... and much more. See the [release notes] for a full accounting. Note that, as 9.4.1 is the first release for which the released artifacts will all be generated by our Hadrian build system, it is possible that there will be packaging issues. If you enounter trouble while using a binary distribution, please open a [ticket]. Likewise, if you are a downstream packager, do consider migrating to [Hadrian] to run your build; the Hadrian build system can be built using `cabal-install`, `stack`, or the in-tree [bootstrap script]. We will be publishing a blog post describing the migration process to Hadrian in the coming weeks. We would like to thank Microsoft Azure, GitHub, IOG, the Zw3rk stake pool, Tweag I/O, Serokell, Equinix, SimSpace, the Haskell Foundation, and other anonymous contributors whose on-going financial and in-kind support has facilitated GHC maintenance and release management over the years. Finally, this release would not have been possible without the hundreds of open-source contributors whose work comprise this release. As always, do give this release a try and open a [ticket] if you see anything amiss. Happy testing, - Ben [downloads.haskell.org] https://downloads.haskell.org/ghc/9.4.1-rc1/ [GHC proposal 0302]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0302-c… [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new [bootstrap script]: https://gitlab.haskell.org/ghc/ghc/-/blob/e2520df3fffa0cf22fb19c5fb872832d1… [Hadrian]: https://gitlab.haskell.org/ghc/ghc/-/blob/e2520df3fffa0cf22fb19c5fb872832d1… [release notes]: https://downloads.haskell.org/~ghc/9.4.1-rc1/docs/users_guide/9.4.1-notes.h…

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Agda Implementors' Meeting XXXI - Edinburgh, 10-16 November 2022
by Orestis Melkonian 06 Aug '22

06 Aug '22

--------------------------------------------------------------- Agda Implementors' Meeting XXXI Call for participation http://wiki.portal.chalmers.se/agda/pmwiki.php?n=Main.AIMXXXI --------------------------------------------------------------- The 31st Agda Implementors' Meeting will take place in Edinburgh, Scotland from Thursday 10 November 2022 to Wednesday 16 November 2022. Note that AIMXXXI was initially planned for 2019 but got postponed due to COVID-19, whilst we had several online meetings XXXII-XXXV. The meeting will consist of: * Presentations concerning theory, implementation, and use cases of Agda and other Agda-like languages. * Discussions around issues related to the Agda language. * Plenty of time to work in, on, under or around Agda, in collaboration with other participants. * A full day dedicated to the EuroProofNet COST action, including talks and discussions on translating libraries and proofs between Agda and other proof assistants. Please direct enquiries about that to Jesper Cockx <Jesper(a)sikanda.be>. To register for AIM XXXI, please fill out the form below and send it to Orestis Melkonian by email <orestis.melkonian(a)ed.ac.uk>, or simply edit the AIMXXI wiki page yourself. > --------------------------------------------------------------- > Registration form for Agda Implementors' Meeting XXXI > > Name: > > Title and optionally abstract (if you want to give a talk or lead a discussion): > > Suggestions for code sprints (optional): > > Dietary restrictions: > > Additional comments: > > --------------------------------------------------------------- More information is available at http://wiki.portal.chalmers.se/agda/pmwiki.php?n=Main.AIMXXXI Please spread the word about this meeting. Best regards, Orestis

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[ANN] plutus-simple-model-0.3 - minimal library to test Plutus/Cardano applications
by Anton Kholomiov 05 Aug '22

05 Aug '22

I’m happy to announce the release of a new version for plutus-simple-model <https://github.com/mlabs-haskell/plutus-simple-model>. It’s a minimal library to write test for Plutus/Cardano applications. It’s easy to use and blazing fast. We use it extensively in Mlabs City to test our Plutus applications. The new release is focused on those main features: - Reduce dependency set to make it as lean as possible. It depends only on plutus and cardano-ledger. - Support for Babbage era (use new features available in Vasil) - Support for Plutus V2 features (inlined datums, reference inputs, reference scripts, forward to redeemer, etc) - Write tutorial <https://mlabs-haskell.github.io/plutus-simple-model/> and update Hackage docs The main thing is Plutus V2 support. Also with cutdown on the list of dependencies it becomes much easier to update and use. I have removed big deps like plutus-apps, ouroboros and cardano-node. With this rewrite also it became 10 times faster. Links: github repo: https://github.com/mlabs-haskell/plutus-simple-model tutorial: https://mlabs-haskell.github.io/plutus-simple-model/ Cheers! Anton

1 0

Capturing typeclass dictionaries from constructors
by Clinton Mead 05 Aug '22

05 Aug '22

Hi All I've asked the following question on StackOverflow, but I thought here might be a good place for it also. Sorry for the crosspost but I'm never sure what the best place to ask Haskell questions is: https://stackoverflow.com/questions/73244177/capturing-typeclass-dictionari… I've copied the StackOverflow post below: --- Below is code that will happily compile (once adding the constraints package). Foo1 and Foo2 are two alternate definitions of Foo, which I can write f1 and f2 sensibly for. However, I *think* Foo3 is reasonable as well. Yet I don't know how to write f3. It seems to me that Haskell should store a pointer to the typeclass dictionary inside the Foo3 constructor, for whatever a is passed when Foo3 is created, so then I should be able to just call silly. Since silly just returns String, it doesn't matter if a has been erased by now, I should be able to happily call the silly pointed to by the dictionary stored in the constructor Foo3. Is my reasoning right? And if so, how can I write f3. Alternative, have I missed something and is there a good reason why I need either Dict or Proxy here because without them I haven't got enough information? {-# LANGUAGE ScopedTypeVariables #-} import Data.Constraint (Dict(Dict), withDict)import Data.Proxy (Proxy) data Aliceclass C a where silly :: Stringinstance C Alice where silly = "Silly Alice" data Foo1 where Foo1 :: Dict (C a) -> Foo1 f1 :: Foo1 -> Stringf1 (Foo1 (dict :: Dict (C a))) = withDict dict $ silly @a data Foo2 where Foo2 :: C a => Proxy a -> Foo2 f2 :: Foo2 -> Stringf2 (Foo2 (_ :: Proxy a)) = silly @a data Foo3 where Foo3 :: C a => Foo3 mkFoo3 :: forall a. C a => Foo3mkFoo3 = Foo3 @a f3 :: Foo3 -> Stringf3 = undefined

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Re: [Haskell-cafe] [ANNOUNCE] GHC 9.4.1-rc1 is now available
by Kazu Yamamoto 02 Aug '22

02 Aug '22

Hi George, > I've duplicated the issue on both of my machines. It would be good to know > if anybody else is seeing it. Kazu, I know you have seen this in the past. > Do you get the same error installing rc1? > When I run sudo make install I get a popup that says: I had no problem on 9.4.1-rc1. "xattr -rc ." and "make install" worked perfectly. macOS Monterey v12.4 Xcode 13.4.1 --Kazu

2 1

Why do I see the escape chars in Emacs with haskell-mode
by Henry Laxen 30 Jul '22

30 Jul '22

Dear Cafe, Greeting Gentle Haskellers, I know this may really be a question for the emacs guys, but I thought for sure someone here has encoutered the same thing and would recognize the problem right away. Here is my progam: module Main where main = xprint "hi" Yes, xprint is intensional, I want an error. I am in haskell mode in emacs. I type C-c C-l running haskell-process-load-file, and get: Hours of hacking await! If I break, you can: 1. Restart: M-x haskell-process-restart 2. Configure logging: C-h v haskell-process-log (useful for debugging) 3. General config: M-x customize-mode 4. Hide these tips: C-h v haskell-process-show-debug-tips .[;1m/home/henry/a.hs:2:8-13: .[;1m.[31merror:.[0m.[0m.[;1m.[0m.[0m.[;1m … • Variable not in scope: xprint :: [Char] -> t • Perhaps you meant ‘print’ (imported from Prelude).[0m.[0m .[;1m/home/henry/a.hs:2:8-13: .[;1m.[31merror:.[0m.[0m.[;1m.[0m.[0m.[;1m … • Variable not in scope: xprint :: [Char] -> t • Perhaps you meant ‘print’ (imported from Prelude).[0m.[0m Compilation failed. but when I swich to the *haskell* buffer and type :r, I get the beautiful, colorized message: [1 of 1] Compiling Main ( /home/henry/a.hs, interpreted ) /home/henry/a.hs:2:8-13: error: • Variable not in scope: xprint :: [Char] -> t • Perhaps you meant ‘print’ (imported from Prelude) | 2 | main = xprint "hi" | ^^^^^^ Failed, no modules loaded. Where the escape sequences have been interpreted correctly. What do I have misconfigured? Please point me in a direction. Thanks in advance. Best wishes, Henry Laxen -- Nadine and Henry Laxen The rest is silence Gral. Manuel Márquez de León 1301 Onix #2302 Zona Urban Rio Never try to teach a pig to sing; Tijuana It wastes your time +52 (333) 667-8633 And it annoys the pig

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Re: [Haskell-cafe] [Haskell] [ANNOUNCE] GHC 9.2.4 released
by Kazu Yamamoto 29 Jul '22

29 Jul '22

Hi, > On a Mac it is still necessary to do > > xattr -rc . > > before doing > > sudo make install For 9.2.4, "xattr -rc ." is not good enough on my Mac (upgraded to v12.5 today). "sudo spctl --global-disable" is necessary, sigh. --Kazu

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[Haskell] [ANNOUNCE] GHC 9.2.4 released
by Zubin Duggal 28 Jul '22

28 Jul '22

The GHC developers are very happy to at announce the availability of GHC 9.2.4. Binary distributions, source distributions, and documentation are available at [`downloads.haskell.org`](https://downloads.haskell.org/ghc/9.2.4). Download Page: https://www.haskell.org/ghc/download_ghc_9_2_4.html Blog Post: https://www.haskell.org/ghc/blog/20220728-ghc-9.2.4-released.html This release will include: - The new `DeepSubsumption` language extension which reverses the effects of the [Simplified Subsumption Proposal] introduced in GHC 9.0. This is an attempt to make GHC 9.2.4 more backwards compatible with GHC 8.10 and eases migration for users who depended on this feature. This extension is enabled by default with the `Haskell2010` and `Haskell98` languages but disabled with the `GHC2021` language originally introduced in GHC 9.2.1. See the [Deep Subsumption Proposal] for more details. - Fixes for segfaults that may arise due to a bug in the implementation of the `keepAlive#` primop. This may regress performance for certain programs which use this primop or functions which use the primop, such as `withForeignPtr`. These regressions are mostly small, but can be larger in certain edge cases. Judicious use of `unsafeWithForeignPtr` when its argument is known not to statically diverge can mitigate these in many cases. It is our judgment that the critical correctness issues justify the regression in performance and that it is important to get a release out with the fix while we work on a better approach which will improve performance for future releases (#21708). We have a [wiki page](https://gitlab.haskell.org/ghc/ghc/-/wikis/proposal/with-combinator) that tracks possible solutions to this problem, and Ben wrote a [blog post](https://www.haskell.org/ghc/blog/20210607-the-keepAlive-story.html) detailing the introduction of the `keepAlive#` primop and its history. - Fixes for a number of miscompilations on AArch64 and other platforms (#21624, #21773, #20735, #21685). - Fixes for segfaults due to bugs in the RTS and GC (#21708, #21880, #21885). - Fixing the behaviour of Ctrl-C with GHCi on Windows (#21889). - ... and much more. See the [release notes] for a full accounting. As some of the fixed issues do affect correctness users are encouraged to upgrade promptly. We would like to thank Microsoft Azure, GitHub, IOG, the Zw3rk stake pool, Tweag I/O, Serokell, Equinix, SimSpace, Haskell Foundation, and other anonymous contributors whose on-going financial and in-kind support has facilitated GHC maintenance and release management over the years. Finally, this release would not have been possible without the hundreds of open-source contributors whose work comprise this release. As always, do give this release a try and open a [ticket] if you see anything amiss. Happy compiling, - Zubin [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new [release notes]: https://downloads.haskell.org/~ghc/9.2.4/docs/users_guide/9.2.4-notes.html [Simplified Subsumption Proposal]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0287-s… [Deep Subsumption Proposal]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0511-d…

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Re: [Haskell-cafe] success on a slightly modified version of your suggestion for 21506
by Carter Schonwald 27 Jul '22

27 Jul '22

that matches my experience, namely that i've successfully installed ghc 9.2.2 on osx 12.4 aka monterey a few times On Sun, Jul 24, 2022 at 12:59 PM George Colpitts <george.colpitts(a)gmail.com> wrote: > Hi Ben > > Thanks for the quick responses particularly on the weekend before your > vacation. > > you wrote: > > What happens > if you try to install to do something like (in the extracted binary > distribution), > > > $ ./configure --prefix=`pwd`/tmp > $ make install # this will fail > $ xattr -rc . > $ make install # perhaps this will finish successfully? > # tmp/bin/ghc --version # GHC should be usable > > > success on both my machines using a slightly modified version of your > suggestion above for 21506: > > ./configure --prefix=`pwd`/tmp # specifying ./tmp seems to be critical > > xattr -rc . # seems to be necessary > also > > sudo make install # seems to works , output ends > with "recache" > > ./tmp/bin/ghc --version # success , although admittedly > the smallest smoke test possible > > You wrote: > > > > Ultimately I think we may just need to bite the bullet and start > properly notarising/codesigning releases (resolving #17418). At this point > we have > spent more time trying to avoid the notarisation requirement than > it would likely take to satisfy it. Unfortunately, this will require > that I find an Apple device somewhere which may take a few weeks. > > > I'm afraid I am on holiday next week but I would quite grateful if we > could arrange for a chat after I return such that we can debug this in > realtime. > > > Sure, we can chat when you return from your vacation. > > Not sure if it is worth trying to fix the release on the basis of what I > write above. My opinion is: it is if we can get reports of at least one > other person having this issue. I am fine with not doing this for 9.4.1 > > I agree that we should raise the priority of "notarising/codesigning > releases (resolving #17418)". My opinion is that it is not worth delaying > 9.4.1 for this. > > Have a great vacation. > > Cheers > George > > > > > > > On Sun, Jul 24, 2022 at 11:33 AM Ben Gamari <ben(a)well-typed.com> wrote: > >> George Colpitts <george.colpitts(a)gmail.com> writes: >> >> > +Kazu Yamamoto <kazu(a)iij.ad.jp> >> > >> > Hi Ben >> > >> > My 2 machines also have: >> > >> > $ spctl --status >> > assessments enabled >> > >> Hmm, interesting. Then I am truly perplexed. >> >> > Speculations: >> > >> > >> /usr/local/lib/ghc-9.4.0.20220721/bin/../lib/x86_64-osx-ghc-9.4.0.20220721/libHSterminfo-0.4.1.5-ghc9.4.0.20220721.dylib >> > is created after xattr -rc . was run so it doesn't have the necessary >> > attributes. Is it possible that ghc developers and/or the test machines >> > have this file on another of the paths in the error message and that is >> why >> > it works for them? >> > >> I'm not sure where this would be but at this point anything is possible. >> What happens >> if you try to install to do something like (in the extracted binary >> distribution), >> >> $ ./configure --prefix=`pwd`/tmp >> $ make install # this will fail >> $ xattr -rc . >> $ make install # perhaps this will finish successfully? >> # tmp/bin/ghc --version # GHC should be usable >> >> > I hope I didn't offend you by asking if the fix had been tested; I >> assume >> > it had been but I thought it was important to rule that out. >> > >> Not to worry; it's a very reasonable question to ask given the >> circumstances. >> >> > More than happy to test. I really appreciate all the work you and others >> > have put into GHC ! >> > >> Ultimately I think we may just need to bite the bullet and start >> properly notarising/codesigning releases (resolving #17418). At this >> point we have >> spent more time trying to avoid the notarisation requirement than >> it would likely take to satisfy it. Unfortunately, this will require >> that I find an Apple device somewhere which may take a few weeks. >> >> I'm afraid I am on holiday next week but I would quite grateful if we >> could arrange for a chat after I return such that we can debug this in >> realtime. >> >> Cheers, >> >> - Ben >> > _______________________________________________ > Glasgow-haskell-users mailing list > Glasgow-haskell-users(a)haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/glasgow-haskell-users >

1 0

ANN: Copilot 3.10
by Ivan Perez 26 Jul '22

26 Jul '22

Dear all, We are very happy to announce the release of Copilot 3.10. Copilot is a runtime verification system implemented as a Haskell DSL that generates hard-realtime C99. You can learn more about it at [1]. This new version of Copilot contains a small but important change in how structs are handled in C functions invoked by the monitors when property violations are detected. This change is API-breaking, so users of Copilot may need to adapt their systems accordingly. The release also contains a number of bug fixes, provides a simplified API, deprecates outdated elements, removes unused code, and relaxes version constraints for dependencies. A full list of changes merged is available at [2]. A substantial effort is being made to achieve NASA's Class D software classification, most notably in terms of development process (which you can partly witness in how issues and PRs are being handled on our github repo), test coverage (mostly with quickcheck), and proofs of correctness of the generated code (with what4). Copilot is being used by the Safety-Critical Avionics Systems Branch (D320) of NASA Langley Research Center to conduct experiments related to flight safety of aerial vehicles. We have also built Ogma [3], a tool that allows us to generate full monitoring applications (e.g., NASA's Core Flight System [4] applications) from requirements in structured natural language. We'd like to take this opportunity to welcome Will Pogge to the team with his first commit, and thank the Galois team for their contributions. We also want to thank everyone who uses and helps promote Copilot; we are seeing increased attention, and gave three talks in the last two months at JPL, USC, and VCU, with two more taking place this month. We invite you all to explore Copilot, to try it, and to extend it. If you like it, please help us draw attention to this work with a star on github or a mention online. Happy Haskelling, The Copilot Team [1] https://github.com/Copilot-Language/copilot [2] https://github.com/Copilot-Language/copilot/milestone/14?closed=1 [3] https://github.com/nasa/ogma [4] https://cfs.gsfc.nasa.gov/

4 7

Munich Haskell Meeting, 2022-07-28 @ 19:30
by Leah Neukirchen 25 Jul '22

25 Jul '22

Dear all, This week, our monthly Munich Haskell Meeting will take place again on Thursday, July 28 at Hirschgarten (Biergarten, self-service area) at 19h30. For details see here: http://muenchen.haskell.bayern/dates.html Please sign up here if you are coming so we'll look out for you. https://dudle.inf.tu-dresden.de/haskell-munich-jul-2022/ Everybody is welcome! cu, -- Leah Neukirchen <leah(a)vuxu.org> https://leahneukirchen.org/

1 0

Re: [Haskell-cafe] [ANNOUNCE] GHC 9.4.1-rc1 is now available
by Ben Gamari 24 Jul '22

24 Jul '22

George Colpitts <george.colpitts(a)gmail.com> writes: > +Kazu Yamamoto <kazu(a)iij.ad.jp> > > Hi Ben > > My 2 machines also have: > > $ spctl --status > assessments enabled > Hmm, interesting. Then I am truly perplexed. > Speculations: > > /usr/local/lib/ghc-9.4.0.20220721/bin/../lib/x86_64-osx-ghc-9.4.0.20220721/libHSterminfo-0.4.1.5-ghc9.4.0.20220721.dylib > is created after xattr -rc . was run so it doesn't have the necessary > attributes. Is it possible that ghc developers and/or the test machines > have this file on another of the paths in the error message and that is why > it works for them? > I'm not sure where this would be but at this point anything is possible. What happens if you try to install to do something like (in the extracted binary distribution), $ ./configure --prefix=`pwd`/tmp $ make install # this will fail $ xattr -rc . $ make install # perhaps this will finish successfully? # tmp/bin/ghc --version # GHC should be usable > I hope I didn't offend you by asking if the fix had been tested; I assume > it had been but I thought it was important to rule that out. > Not to worry; it's a very reasonable question to ask given the circumstances. > More than happy to test. I really appreciate all the work you and others > have put into GHC ! > Ultimately I think we may just need to bite the bullet and start properly notarising/codesigning releases (resolving #17418). At this point we have spent more time trying to avoid the notarisation requirement than it would likely take to satisfy it. Unfortunately, this will require that I find an Apple device somewhere which may take a few weeks. I'm afraid I am on holiday next week but I would quite grateful if we could arrange for a chat after I return such that we can debug this in realtime. Cheers, - Ben

1 0

Re: [Haskell-cafe] [ANNOUNCE] GHC 9.4.1-rc1 is now available
by Ben Gamari 23 Jul '22

23 Jul '22

George Colpitts <george.colpitts(a)gmail.com> writes: > Hi Ben > > /ust/bin/xattr exists on my machine. Running "xattr -rc ." manually does > not fix the bug as noted at the start of 21506. It was sufficient in the > past but no longer fixes this error. As noted farther down in 21506 > > the workaround given in #17418 </ghc/ghc/-/issues/17418> no longer works. > It did not work in 9.2.2 either. The current workaround is similar to what > Kazu explained in > https://twitter.com/kazu_yamamoto/status/1500643489985761282 > > sudo xattr -rc . > > sudo spctl --global-disable > > ./configure > > sudo make install > > sudo spctl --global-enable > > It seems there are files created during sudo make install that have an > issue as xattr -rc . was never run on them. Perhaps this is related to > using Hadrian. Is it possible that the fix that was made was never tested? > I tested the change both manually and via CI on the hardware that I have access to; in both cases installing the binary distribution resulted in a functional compiler. However, given how the effects of SIP are essentially undocumented, it is very hard to know what variables may be at play here. Running spctl --status on the machine on which I tested claims: > spctl --status objc[48908]: Class SPExecutionPolicy is implemented in both /System/Library/PrivateFrameworks/SystemPolicy.framework/Versions/A/SystemPolicy and /usr/sbin/spctl. One of the two will be used. Which one is undefined. objc[48908]: Class AppWrapper is implemented in both /System/Library/PrivateFrameworks/SystemPolicy.framework/Versions/A/SystemPolicy and /usr/sbin/spctl. One of the two will be used. Which one is undefined. objc[48908]: Class AppWrapperPolicyResult is implemented in both /System/Library/PrivateFrameworks/SystemPolicy.framework/Versions/A/SystemPolicy and /usr/sbin/spctl. One of the two will be used. Which one is undefined. objc[48908]: Class AppWrapperPolicy is implemented in both /System/Library/PrivateFrameworks/SystemPolicy.framework/Versions/A/SystemPolicy and /usr/sbin/spctl. One of the two will be used. Which one is undefined. objc[48908]: Class SPLog is implemented in both /System/Library/PrivateFrameworks/SystemPolicy.framework/Versions/A/SystemPolicy and /usr/sbin/spctl. One of the two will be used. Which one is undefined. objc[48908]: Class MIS is implemented in both /System/Library/PrivateFrameworks/SystemPolicy.framework/Versions/A/SystemPolicy and /usr/sbin/spctl. One of the two will be used. Which one is undefined. objc[48908]: Class SPExecutionHistoryItem is implemented in both /System/Library/PrivateFrameworks/SystemPolicy.framework/Versions/A/SystemPolicy and /usr/sbin/spctl. One of the two will be used. Which one is undefined. objc[48908]: Class SPExecutionPolicyItem is implemented in both /System/Library/PrivateFrameworks/SystemPolicy.framework/Versions/A/SystemPolicy and /usr/sbin/spctl. One of the two will be used. Which one is undefined. objc[48908]: Class SPDeveloperPolicy is implemented in both /System/Library/PrivateFrameworks/SystemPolicy.framework/Versions/A/SystemPolicy and /usr/sbin/spctl. One of the two will be used. Which one is undefined. objc[48908]: Class GKScanResult is implemented in both /System/Library/PrivateFrameworks/SystemPolicy.framework/Versions/A/SystemPolicy and /usr/sbin/spctl. One of the two will be used. Which one is undefined. assessments enabled Which to me suggests that SIP (which, I imagine, is responsible for #21506) is enabled. However, the lack of comprehensive documentation here makes it very hard to say with certainty what might differ between your machine and mine. Without more information I don't know how to proceed here. Perhaps someone (Moritz or Simon, perhaps) with more familiarity with macOS has some insight? Thanks for your help in testing, George! Cheers, - Ben

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Re: [Haskell-cafe] [ANNOUNCE] GHC 9.4.1-rc1 is now available
by Ben Gamari 23 Jul '22

23 Jul '22

George Colpitts <george.colpitts(a)gmail.com> writes: > Hi Ben, > > I expected https://gitlab.haskell.org/ghc/ghc/-/issues/21506 (ghc-9.4.1-alpha1 > does not install on macos: ghc-pkg-9.4.0-20220501 cannot be opened because > the developer cannot be verified) to be fixed in rc1 but it is not. Are my > expectations wrong? What is the ETA for fixing it? > Thanks for letting us know, George. The fix that we have [1] is present in 9.4.1-rc1. If that commit doesn't resolve the issue then there is something that we don't understand. Does `/usr/bin/xattr` exist? Running `xattr -rc` manually on the binary distribution allow you to run the compiler? Cheers, - Ben [1] https://gitlab.haskell.org/ghc/ghc/-/commit/641972d65b476aac11424bde6c3bcfd…

1 0

An org backend to Haddock
by Yuchen Pei 21 Jul '22

21 Jul '22

Hello, I decided to write an Org backend to Haddock[1], so that haskell library documentation can be generated in org mode markup. Compared to the existing backends (html, latex and hoogle), the org format allows utilising features like the infinite levels of heading hierarchy, flexible folding / unfolding, cross-package linking, jumping to any declaration with org-goto and the endless potentials of emacs customisation. It seems to me most information and haskell language features one can find on displayed on hackage are supported by the org backend and included in the output org files, though there are still some rough edges and unsupported language features (like infix declarations and linear types) which I aim to fix. Some example output can be found at [2] (I will need to rename the "assets" part of the url as it is not accurate), including base[4], ghc-prim[5] and ghc-lib-parser[6] (I use it for reference of the GHC API as it is easier to build than GHC). For more information, check out the README file[3]. Given this is not the official version of haddock and my changes are in haddock-api, I'm calling it haddorg-api, for lack of a better name / approach. I'll be happy to contribute my changes upstream if a different license covering my contribution (AGPLv3+) is accepted. Let me know what you think. [1] https://g.ypei.me/haddock.git/tree/haddock-api [2] https://ypei.org/assets/haddorg-output/ [3] https://g.ypei.me/haddock.git/tree/haddock-api/README.org [4] https://ypei.org/assets/haddorg-output/base-4.16.1.0.org.gz [5] https://ypei.org/assets/haddorg-output/ghc-prim-0.8.0.org.gz [6] https://ypei.org/assets/haddorg-output/ghc-lib-parser-9.2.2.20220307.org.gz Best, Yuchen -- PGP Key: 47F9 D050 1E11 8879 9040 4941 2126 7E93 EF86 DFD0 <https://ypei.org/assets/ypei-pubkey.txt>

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Postdoc Vacancy at St Andrews
by Christopher Brown 20 Jul '22

20 Jul '22

The Programming Languages Group at the University of St Andrews seeks a post-doctoral research fellow for a fixed 12-month position. Details of the position can be found here: https://www.vacancies.st-andrews.ac.uk/Vacancies/W/4238/0/352367/889/resear… Vacancy Description School of Computer Science Salary: £34,304 per annum Start date: 1 October 2022 or as soon as possible thereafter Fixed-term: 12 months Applications are sought for a committed Post-doctoral Research Fellow to work with Dr Chris Brown conducting research for a EPSRC funded project entitled Energise: Refactorings and Skeletons for Energy-Aware Applications on High-Performance Embedded Systems. The primary duties will be to implementing refactorings for target languages such as C; proving general soundness of the refactorings using e.g. dependent types; developing new programming abstractions (skeletons) for abstracting common energy-reducing programming patterns; running experiments; writing proofs of correctness. The successful applicant will have (or be near to completion of) a PhD in Programming Languages with expertise in formal semantics of programming languages, compilers, program transformation, lightweight formal methods (including, e.g. dependent types) and/or knowledge of parallelism and non-functional properties, including energy. The post is available on a fixed-term basis for 12 months starting 1st October or as soon as possible thereafter. Further details of the project can be found by contacting Dr Christopher Brown (cmb21(a)st-andrews.ac.uk<mailto:cmb21@st-andrews.ac.uk>). Applications are particularly welcome from women, people from the Black, Asian and Minority Ethnic (BAME) community, and other protected characteristics who are under-represented in research posts at the University. Equality, diversity and inclusion are at the heart of the St Andrews experience. We strive to create a fair and inclusive culture demonstrated through our commitment to diversity awards (Athena Swan, Carer Positive, LGBT Charter, Race Charters and Stonewall). We celebrate diversity by promoting profiles of BAME, LGBTIQ+ staff and supporting networks including the Staff BAME Network; Staff with Disabilities Network; Staff LGBTIQ+ Network; and the Staff Parents & Carers Network. Full details available online: https://www.st-andrews.ac.uk/hr/edi/ Closing Date: 29 July 2022 Interview Date: 23 August 2022 Please quote ref:AR2699GB School of Computer Science Salary: £34,304 per annum Start date: 1 October 2022 or as soon as possible thereafter Fixed-term: 12 months

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Re: [Haskell-cafe] An org backend to Haddock
by Yuchen Pei 19 Jul '22

19 Jul '22

On Tue 2022-07-19 21:58:26 +0800, Ihor Radchenko wrote: > Yuchen Pei <id(a)ypei.org> writes: > >> Given this is not the official version of haddock and my changes are in >> haddock-api, I'm calling it haddorg-api, for lack of a better name / >> approach. I'll be happy to contribute my changes upstream if a >> different license covering my contribution (AGPLv3+) is accepted. >> >> Let me know what you think. > > I am pretty sure that you are asking the Haskell people for upstreaming > ;) Yes - I sent the email to both haskell-cafe and emacs-orgmode, but upstream here means haddock / haddock-api indeed, thanks for clarifying. > > From Org side, it is always welcome when other Free software projects > are making use of Org. > > Also, I looked into > https://g.ypei.me/haddock.git/tree/haddock-api/src/Haddock/Backends/Org/Typ… > > Beware of possible edge cases with "*/~|" in formatting. I am not > sure if text containing such symbols is possible as an input for your > library, but if it is, things may get formatted wrongly. > > For example, text containing "|" anywhere inside a table field must have > "|" escaped using \vert entity. The markup can be escaped using > zero-width space. True. I have not addressed these edge cases in my code, except a quick hack to prepend a space whenever any line a src block / result block has a leading star. Tables on the other hand are extremely rare in Haskell package documentation strings, and having a | in them is even rarer. I do wonder what is the best way to handle cross-package links. Currently I'm using CUSTOM_ID in the format of package-name-x.y.z.Module.Name.IdentifierName, as well as Module.Name.IdentifierName. But this is a "one big org file" approach, and can make navigation slow when say the org file reaches 15+MB in size. Ideally one should be able to navigate the a hackage worth of documentations easily, with working cross-package links and low latency org-goto to jump to any identifier or module, but I don't see how to achieve that. To be further investigated. > > Best, > Ihor Best, Yuchen -- PGP Key: 47F9 D050 1E11 8879 9040 4941 2126 7E93 EF86 DFD0 <https://ypei.org/assets/ypei-pubkey.txt>

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2nd CFP - IFL22 - The 34th Symposium on Implementation and Application of Functional Languages
by Pieter Koopman 15 Jul '22

15 Jul '22

*CALL FOR PAPERS: * The 34th Symposium on Implementation and Application of Functional Languages (IFL 2022) *Submission and registration are open.* See https://ifl22.github.io/. Copenhagen, August 31st-September 2nd, 2022 *Important dates * Draft paper submission: August 7th, 2022 Draft paper notification: August 9th, 2022 Early registration deadline: August 12th, 2022 Late registration deadline: September 2nd, 2022 Symposium: August 31st-September 2nd, 2022 (3 days) *Scope * The goal of the IFL symposia is to bring together researchers actively engaged in the implementation and application of functional and function-based programming languages. IFL 2022 will be a venue for researchers to present and discuss new ideas and concepts, work in progress, and publication-ripe results related to the implementation and application of functional languages and function-based programming. Topics of interest to IFL include, but are not limited to: * language concepts * type systems, type checking, type inferencing * compilation techniques * staged compilation * run-time function specialization * run-time code generation * partial evaluation * abstract interpretation * metaprogramming * generic programming * automatic program generation * array processing * concurrent/parallel programming * concurrent/parallel program execution * embedded systems * web applications * embedded domain specific languages * security * novel memory management techniques * run-time profiling performance measurements * debugging and tracing * virtual/abstract machine architectures * validation, verification of functional programs * tools and programming techniques * industrial applications *Submissions and peer-review * Following IFL tradition, IFL 2022 will use a post-symposium review process to produce the formal proceedings. Before the symposium authors submit draft papers. These draft papers will be screened by the program chair to make sure that they are within the scope of IFL. The draft papers will be made available to all participants at the symposium. Each draft paper is presented by one of the authors at the symposium. Notice that it is a requirement that accepted draft papers are presented physically at the symposium. After the symposium, a formal review process will take place, conducted by the program committee. Reviewing is single blind. There will be at least 3 reviews per paper. The reviewers have 6 weeks to write their reviews. For the camera-ready version the authors can make minor revisions which are accepted without further reviewing. Contributions submitted for the draft paper deadline must be between two and twelve pages long. For submission details, please consult the IFL 2022 website at https://ifl22.github.io/. *Where * IFL 2022 will be held physically in Copenhagen, Denmark, arranged by DIKU at the University of Copenhagen. See the IFL 2022 website at https://ifl22.github.io/ for more information. [image: beacon]

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What is the exponential version of dependently-typed Vector and Tensor?
by Johannes Riecken 15 Jul '22

15 Jul '22

I noticed that the definitions of Vector and Tensor have a parallel structure. Vector is an ornamentation of the Peano natural numbers, and Tensor is the parallel construction with multiplication and the multiplicative identity, except that the factors are stored in a list instead of directly multiplying, so that the dependent typing can ensure that the number of elements in the tensor is indeed equal to the product of these factors. (To make it more parallel, the Nat in Vector could be replaced with a list of ones.) ```haskell {-# LANGUAGE AllowAmbiguousTypes #-} {-# LANGUAGE DataKinds #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE RankNTypes #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeOperators #-} import GHC.TypeLits import Data.Kind import Numeric.Natural import Data.Proxy data Vector (n :: Nat) a where Nil :: Vector 0 a Cons :: a -> Vector n a -> Vector (n + 1) a data Tensor :: forall n. Vector n Nat -> Type -> Type where Scalar :: a -> Tensor Nil a Dimension :: Vector n (Tensor d a) -> Tensor (Cons n d) a ``` That made me wonder what the exponential version with functions would look like and if that is a useful concept, too, or one that also exists in maths? As going from Vector to Tensor isn't completely mechanical, I had trouble figuring out myself how to go from Tensor to the next higher data structure. Cheers, Johannes

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stack and package candidates
by Henning Thielemann 15 Jul '22

15 Jul '22

In a project my stack.yaml contains this line: - url: https://hackage.haskell.org/package/foobar-0.0/candidate/foobar-0.0.tar.gz This works, but if I update the foobar release candidate then Stack will not notice and stick to the old version. How can I invalidate or remove the cached foobar version?

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Folding nested foldables -- Known pattern?
by Ivan Perez 12 Jul '22

12 Jul '22

Spam detection software, running on the system "mail.haskell.org", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see @@CONTACT_ADDRESS@@ for details. Content preview: Hi cafÃ© TL;DR: In Copilot, we have an ad-hoc notion of a nestable data structure that can be folded into a list. I'm trying to rely on standard classes as much as possible. Is there a known class to capture the idea of folding nested data structures (e.g., transitive foldable?) [...] Content analysis details: (5.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (ivanperezdominguez[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record -0.0 BAYES_40 BODY: Bayes spam probability is 20 to 40% [score: 0.2680] 5.0 UNWANTED_LANGUAGE_BODY BODY: Message written in an undesired language 0.0 HTML_MESSAGE BODY: HTML included in message 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid The original message was not completely plain text, and may be unsafe to open with some email clients; in particular, it may contain a virus, or confirm that your address can receive spam. If you wish to view it, it may be safer to save it to a file and open it with an editor.

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mastered Haskell and need a new challenge???
by Anand, Christopher 11 Jul '22

11 Jul '22

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Call for Reviewers APLAS 2022 Artifact Evaluation Committee
by Arpita Dutta 01 Jul '22

01 Jul '22

Dear all, The /20th Asian Symposium on Programming Languages and Systems/ (APLAS'22) is going to be holding its first /Artifact Evaluation Committee/ (AEC). The artifact evaluation process aims to promote, share, and catalogue the research artifacts of papers accepted to the APLAS research track. We are looking for motivated researchers at all academic stages (Ph.D. Students, Researchers, Lecturers, & Professors) to join us on the inaugural APLAS'22 AEC. The self-nomination form is available at: https://forms.gle/rJREG9DiFQHegZmD9 To nominate other people please use the following form: https://forms.gle/KFiQYLjELMsEjGLp8 As a committee member, your primary responsibility will be to review artifacts submitted by authors of accepted papers and ensure that the artifact is a faithful representation of the accepted paper's results. This will involve interacting with some tooling provided by the authors, check if the results of the main paper are consistent with the claims in the paper, and are also reproducible for researchers to come. APLAS will use a three-phase artifact review process: Kick-The-Tyres; Review the Artifact; and Iron-out-the-Wrinkles. Reviewing guidance for committee members will be made available once the committee has been formed. We will close nominations on: Friday 08 July 2022 (AOE) and notify the selected committee members on: Friday 15 July 2022 (AOE) We expect most of the reviewing process to be performed between 22nd August 2022 and 19th September 2022. We expect each artifact to take around eight hours to review and we will look to assign each reviewer three to four reviews. For each artifact, we will assign a Lead Reviewer to lead the reviewing process. Salient information about the reviewing process can be found online: https://2022.splashcon.org/track/aplas-2022-aec#Reviewer-Information<https://2022.splashcon.org/track/aplas-2022-aec#Reviewer-Information> Come join us to improve the quality of research in our field! Thanks Arpita Dutta and Jan de Muijnck-Hughes APLAS'22 AEC Co-Chairs. This call was adapted from the PLDI'22 AEC Call for Nominations.

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Where does η-equivalence stop?
by Hécate 30 Jun '22

30 Jun '22

Hi Café! I was wondering if anyone knew of a centralised list of occurrences where GHC Haskell stops upholding η-equivalence. I am interested in both type changes and operational semantics. So far I've collected the following things: * Rank-2 types * Monomorphism restriction * The presence of seq * Non-pedantic bottoms One source is the GHC Manual¹, and Neil Mitchell pointed me to the list of bugs and limitations of HLint². If you have other examples, or explanations of the mechanisms at play here, I would be very interested, and intend to upstream those in the GHC manual. Cheers, Hécate [¹] https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/bugs.html#e… [²] https://github.com/ndmitchell/hlint#bugs-and-limitations -- Hécate ✨ 🐦: @TechnoEmpress IRC: Hecate WWW: https://glitchbra.in RUN: BSD

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Munich Haskell Meeting, 2022-06-28 @ 19:30
by Leah Neukirchen 26 Jun '22

26 Jun '22

Dear all, Next week, our monthly Munich Haskell Meeting will take place again on Tuesday, June 28 at Hirschgarten (Biergarten, self-service area) at 19h30. For details see here: http://muenchen.haskell.bayern/dates.html If you plan to join, please add yourself to this dudle so we'll look out for you. It is OK to add yourself to the dudle anonymously or pseudonymously. https://dudle.inf.tu-dresden.de/haskell-munich-jun-2022/ Everybody is welcome! cu, -- Leah Neukirchen <leah(a)vuxu.org> https://leahneukirchen.org/

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GHC 9.4.1-alpha3 now available
by Ben Gamari 24 Jun '22

24 Jun '22

The GHC developers are happy to announce the availability of the third alpha release of the GHC 9.4 series. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org](https://downloads.haskell.org/ghc/9.4.1-alpha3). This major release will include: - A new profiling mode, `-fprof-late`, which adds automatic cost-center annotations to all top-level functions *after* Core optimisation has run. This incurs significantly less performance cost while still providing informative profiles. - A variety of plugin improvements including the introduction of a new plugin type, *defaulting plugins*, and the ability for typechecking plugins to rewrite type-families. - An improved constructed product result analysis, allowing unboxing of nested structures, and a new boxity analysis, leading to less reboxing. - Introduction of a tag-check elision optimisation, bringing significant performance improvements in strict programs. - Generalisation of a variety of primitive types to be levity polymorphic. Consequently, the `ArrayArray#` type can at long last be retired, replaced by standard `Array#`. - Introduction of the `\cases` syntax from [GHC proposal 0302] - A complete overhaul of GHC's Windows support. This includes a migration to a fully Clang-based C toolchain, a deep refactoring of the linker, and many fixes in WinIO. - Support for multiple home packages, significantly improving support in IDEs and other tools for multi-package projects. - A refactoring of GHC's error message infrastructure, allowing GHC to provide diagnostic information to downstream consumers as structured data, greatly easing IDE support. - Significant compile-time improvements to runtime and memory consumption. - On overhaul of our packaging infrastructure, allowing full traceability of release artifacts and more reliable binary distributions. - ... and much more. See the [release notes] for a full accounting. Note that, as 9.4.1 is the first release for which the released artifacts will all be generated by our Hadrian build system, it's possible that there will be packaging issues. If you enounter trouble while using a binary distribution, please open a [ticket]. Likewise, if you are a downstream packager, do consider migrating to [Hadrian] to run your build; the Hadrian build system can be built using `cabal-install`, `stack`, or the in-tree [bootstrap script]. We would like to thank Microsoft Azure, GitHub, IOG, the Zw3rk stake pool, Tweag I/O, Serokell, Equinix, SimSpace, and other anonymous contributors whose on-going financial and in-kind support has facilitated GHC maintenance and release management over the years. Finally, this release would not have been possible without the hundreds of open-source contributors whose work comprise this release. As always, do give this release a try and open a [ticket] if you see anything amiss. Happy testing, - Ben [GHC proposal 0302]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0302-c… [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new [bootstrap script]: https://gitlab.haskell.org/ghc/ghc/-/blob/e2520df3fffa0cf22fb19c5fb872832d1… [Hadrian]: https://gitlab.haskell.org/ghc/ghc/-/blob/e2520df3fffa0cf22fb19c5fb872832d1… [release notes]: https://downloads.haskell.org/~ghc/9.4.1-alpha3/docs/users_guide/9.4.1-note…

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A pattern does not admit a type signature.
by Ignat Insarov 23 Jun '22

23 Jun '22

Hello Café! I cannot understand why the following code does not compile. ```Haskell {-# LANGUAGE UnicodeSyntax #-} {-# LANGUAGE TypeOperators #-} {-# LANGUAGE DataKinds #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE PatternSynonyms #-} module Arity where import GHC.TypeNats data Vektor length value where Sektor ∷ value → Vektor length value → Vektor (1 + length) value Mektor ∷ Vektor 0 value pattern (:>) ∷ value → Vektor length value → Vektor (1 + length) value pattern value :> values = Sektor value values infixr 5 :> ``` The error: ``` • Could not deduce: length1 ~ length from the context: (1 + length) ~ (1 + length1) bound by a pattern with constructor: Sector :: forall value (length :: Natural). value -> Vector length value -> Vector (1 + length) value, in a pattern synonym declaration at Arity.hs:16:27-45 Expected: Vector length value Actual: Vector length1 value ‘length1’ is a rigid type variable bound by a pattern with constructor: Sector :: forall value (length :: Natural). value -> Vector length value -> Vector (1 + length) value, in a pattern synonym declaration at Arity.hs:16:27-45 ‘length’ is a rigid type variable bound by the signature for pattern synonym ‘:>’ at Arity.hs:15:16-70 • In the declaration for pattern synonym ‘:>’ • Relevant bindings include values :: Vector length1 value (bound at Arity.hs:16:40) | 16 | pattern value :> values = Sector value values | ^^^^^^ ``` If I omit the pattern's type signature, the code compiles. What is going on?

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Onward! Papers 2022 - CfP
by Andreea Costea 21 Jun '22

21 Jun '22

*** Onward! Papers 2022 Call for Papers *** Onward! is a premier multidisciplinary conference focused on everything to do with programming and software: including processes, methods, languages, communities and applications. Onward! is more radical, more visionary and more open than other conferences to ideas that are well-argued but not yet proven. We welcome different ways of thinking about, approaching and reporting on programming language and software engineering research. Onward! Papers is looking for grand visions and new paradigms that could make a big difference in how we will one day build software. But it is not looking for research-as-usual papers—conferences like OOPSLA are the place for that. Those conferences require rigorous validation such as theorems or empirical experiments, which are necessary for scientific progress, but which typically preclude discussion of early-stage ideas. Onward! papers must also supply some degree of validation because mere speculation is not a good basis for progress. However, Onward! accepts less rigorous methods of validation such as compelling arguments, exploratory implementations, and substantial examples. The use of worked-out examples to support new ideas is strongly encouraged. https://2022.splashcon.org/track/splash-2022-Onward-papers The submission deadline is July 10th, 2022 AOE.

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Re: [Haskell-cafe] traversal with an arrow
by Olaf Klinke 19 Jun '22

19 Jun '22

> On Fri, Jun 17, 2022 at 05:01:55PM +0200, Olaf Klinke wrote: > > Is there prior art to the following generalisation? > > > traverseArrow :: Traversable t => a x y -> a (t x) (t y) > > Perhaps you are looking for this: > > https://github.com/tomjaguarpaw/Arrows2/issues/3#issuecomment-561973678 > Thanks Tom, can you explain what's behind this implementation, for those unfamiliar with arrow syntax? I guess [*] that the Traversal type used is a manifestation of the fact that one can transform any traversable structure (t a) into ([a],t ()) and sort the contents of the linked list back into their original places? This way, arbitrary traversals can be reduced to traversals over linked lists. Then the ArrowChoice is needed to pattern match on the list constructors? E. Kmett's profunctor implementation wanderA, linked to from the end of the discussion, seems to be missing from the current Data.Profunctor.Traversing module. Olaf [*] Structurally, Traversal a r b ~ Free (Const a :*: ((->) r)) b and also their Applicative instances seem to match on first glance. In particular, Traversal a () b ~ ([a],b) whence traversal :: Traversable t => t a -> Traversal a b (t b) can be specialized to traversal :: Traversable t => t a -> ([a],t ())

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traversal with an arrow
by Olaf Klinke 18 Jun '22

18 Jun '22

Dear Café, Is there prior art to the following generalisation? A Hoogle search for the type signatures did not turn up anything. import Control.Arrow import Control.Monad (foldM) -- | Categories which every Traversable is a functor in. -- For Traversable t, the instance should satisfy -- -- @ -- foldMapArrow f = foldMapArrow id . traverseArrow f -- @ class Arrow a => ArrowTraverse a where traverseArrow :: Traversable t => a x y -> a (t x) (t y) foldArrow :: Foldable t => a (y,x) y -> a (y,t x) y instance ArrowTraverse (->) where traverseArrow = fmap foldArrow f = uncurry ((foldl.curry) f) instance Monad m => ArrowTraverse (Kleisli m) where traverseArrow (Kleisli k) = Kleisli (mapM k) foldArrow (Kleisli k) = (Kleisli . uncurry) (foldM (curry k)) -- | Generalizes foldMap. -- For Kleisli m, this function is also known as foldMapM. foldMapArrow :: (ArrowTraverse a, Foldable f, Monoid y) => a x y -> a (f x) y foldMapArrow f = (arr (const mempty) &&& id) >>> foldArrow ((id *** f) >>> arr (uncurry mappend)) The thing is that there are more instances for this class, for example by using Ross Paterson's arrow transformers [1]. I found myself implementing an arrow that is a Kleisli arrow with a reader context. Neither the standard arrow machinery nor the arrows package seem to grant me the power to write a traverseArrow for it. Either it can't be done, or my arrow-fu is not strong enough. Olaf [1] https://hackage.haskell.org/package/arrows

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邀请： Deadline Extended: 26th Brazilian Symposiu... @ 2022年6月17日 (周五) 下午6:30 - 下午7:30 (CST) (haskell-cafe@haskell.org)
by rippletc＠gmail.com 17 Jun '22

17 Jun '22

[Haskell-cafe] Deadline Extended: 26th Brazilian Symposium on Programming Languages (SBLP 2022) 2022年6月17日 (星期五) ⋅ 下午6:30 – 下午7:30 台北标准时间通过 Google Meet 加入视频会议 https://meet.google.com/wvx-gvgo-mmj?hs=224 SBLP 2022 is the 26th edition of the Brazilian Symposium on Programming Languages. It is promoted by the Brazilian Computer Society (SBC) and constitutes a forum for researchers, students, and professionals to present and discuss ideas and innovations in the design, definition, analysis, implementation, and practical use of programming languages. SBLP's first edition was in 1996. Since 2010, it has been part of CBSoft, the Brazilian Conference on Software: Theory and Practice. The Conference is planned to be held on October 3-7, 2022, fully online. Submission Guidelines Papers can be written in Portuguese or English. Submissions in English are encouraged considering that only accepted papers written in English will appear in the proceedings, usually indexed in the ACM Digital Library (to be confirmed). The acceptance of a paper implies the registration of at lea... 组织者 rippletc(a)gmail.com rippletc(a)gmail.com 邀请对象 rippletc(a)gmail.com- 组织者 cdvasconcellos(a)hotmail.com haskell-cafe(a)haskell.org 查看所有邀请对象信息 https://calendar.google.com/calendar/event?action=VIEW&eid=M3RxajQ0a2pkamF2… 回复 haskell-cafe(a)haskell.org 的邀请并查看更多详细信息 https://calendar.google.com/calendar/event?action=VIEW&eid=M3RxajQ0a2pkamF2… 您可以选择是否参加。 ~~//~~ 来自 Google 日历的邀请：https://calendar.google.com/calendar/ 您之所以收到这封电子邮件，是因为您是活动的参加者。如要停止接收有关此活动的后续更新，请拒绝此活动。转发此邀请后，任何收件人都可以向组织者发送回复，也可以被添加到邀请对象列表；无论其邀请状态为何，他们都可以邀请其他人；他们还可以修改您的回复。了解详情https://support.google.com/calendar/answer/37135#forwarding

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Post Doc Vacancy at St Andrews
by Christopher Brown 17 Jun '22

17 Jun '22

The Programming Languages Group at the University of St Andrews seeks a post-doctoral research fellow for a fixed 12-month position. Details of the position can be found here: https://www.vacancies.st-andrews.ac.uk/Vacancies/W/4238/0/352367/889/resear… Vacancy Description School of Computer Science Salary: £34,304 per annum Start date: 1 October 2022 or as soon as possible thereafter Fixed-term: 12 months Applications are sought for a committed Post-doctoral Research Fellow to work with Dr Chris Brown conducting research for a EPSRC funded project entitled Energise: Refactorings and Skeletons for Energy-Aware Applications on High-Performance Embedded Systems. The primary duties will be to implementing refactorings for target languages such as C; proving general soundness of the refactorings using e.g. dependent types; developing new programming abstractions (skeletons) for abstracting common energy-reducing programming patterns; running experiments; writing proofs of correctness. The successful applicant will have (or be near to completion of) a PhD in Programming Languages with expertise in formal semantics of programming languages, compilers, program transformation, lightweight formal methods (including, e.g. dependent types) and/or knowledge of parallelism and non-functional properties, including energy. The post is available on a fixed-term basis for 12 months starting 1st October or as soon as possible thereafter. Further details of the project can be found by contacting Dr Christopher Brown (cmb21(a)st-andrews.ac.uk<mailto:cmb21@st-andrews.ac.uk>). Applications are particularly welcome from women, people from the Black, Asian and Minority Ethnic (BAME) community, and other protected characteristics who are under-represented in research posts at the University. Equality, diversity and inclusion are at the heart of the St Andrews experience. We strive to create a fair and inclusive culture demonstrated through our commitment to diversity awards (Athena Swan, Carer Positive, LGBT Charter, Race Charters and Stonewall). We celebrate diversity by promoting profiles of BAME, LGBTIQ+ staff and supporting networks including the Staff BAME Network; Staff with Disabilities Network; Staff LGBTIQ+ Network; and the Staff Parents & Carers Network. Full details available online: https://www.st-andrews.ac.uk/hr/edi/ Closing Date: 29 July 2022 Interview Date: 23 August 2022 Please quote ref:AR2699GB School of Computer Science Salary: £34,304 per annum Start date: 1 October 2022 or as soon as possible thereafter Fixed-term: 12 months

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How to override binary package
by ☂Josh Chia (謝任中) 14 Jun '22

14 Jun '22

Hi, Given that binary is one of the packages that comes with GHC, it seems that it can't be overridden with my own version using the standard ways (e.g. extra-deps in stack.yaml), at least not easily. On GHC 9.2.3, using stack, I would like to use my own version from my github repo. I've tried extra-deps referencing the github repo commit and it did not work; judging by the behavior of some functions, I was still getting the standard binary package instead of my own version. Is there a way to override? Josh

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State Monad Tutorial
by danon 14 Jun '22

14 Jun '22

Saw the discussion on the https://wiki.haskell.org/Talk:State_Monad I don´t have an account on the wiki. If anyone is interested in a small practical example of how to State Monad. I may have 1 or 2. Kind Regards dhj

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CALL FOR PAPERS - IFL22 - The 34th Symposium on Implementation and Application of Functional Languages
by Pieter Koopman 13 Jun '22

13 Jun '22

*CALL FOR PAPERS - The 34th Symposium on Implementation and Application of Functional Languages* *Important dates* Draft paper submission: 7th of August 2022 Draft paper notification: 9th of August 2022 Registration deadline: 12th of August 2022 Symposium: 31th of August to 2nd of September *Scope* The goal of the IFL symposia is to bring together researchers actively engaged in the implementation and application of functional and function-based programming languages. IFL 2022 will be a venue for researchers to present and discuss new ideas and concepts, work in progress, and publication-ripe results related to the implementation and application of functional languages and function-based programming. Topics of interest to IFL include, but are not limited to: * language concepts * type systems, type checking, type inferencing * compilation techniques * staged compilation * run-time function specialization * run-time code generation * partial evaluation * abstract interpretation * metaprogramming * generic programming * automatic program generation * array processing * concurrent/parallel programming * concurrent/parallel program execution * embedded systems * web applications * embedded domain specific languages * security * novel memory management techniques * run-time profiling performance measurements * debugging and tracing * virtual/abstract machine architectures * validation, verification of functional programs * tools and programming techniques * industrial applications *Submissions and peer-review* Following IFL tradition, IFL 2022 will use a post-symposium review process to produce the formal proceedings. Before the symposium authors submit draft papers. These draft papers will be screened by the program chair to make sure that they are within the scope of IFL. The draft papers will be made available to all participants at the symposium. Each draft paper is presented by one of the authors at the symposium. After the symposium, a formal review process will take place, conducted by the program committee. Reviewing is single blind. There will be at least 3 reviews per paper. The reviewers have 6 weeks to write their reviews. For the camera-ready version the authors can make minor revisions which are accepted without further reviewing. *Where* IFL 2022 will be held physically in Copenhagen, Denmark, arranged by DIKU at the University of Copenhagen. See the IFL 2022 website at https://ifl22.github.io/ for more information. [image: beacon]

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pipes Producer combination
by PICCA Frederic-Emmanuel 13 Jun '22

13 Jun '22

Hello, I would like to combine Producers in order to create a Producer of another type whcih combine these values I want a Producer of the 'A' type data A :: A a b by I have a Producer of 'a' values and another on of 'b' values. what is the best way to create from thoses two producers a Producer of 'A' ? Is ther a Generic way to automatically generate these combine Producers. In my programmes, I will have plenty of these combine Producers. thanks for considering. Cheers Frederic

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Phase correction?
by Mario Lang 08 Jun '22

08 Jun '22

Hi. This is more a math question then a Haskell specific thing. However, Haskell fits nicely to write down the problem as executable "pseudo" code, so here I am, knowing that you all can read this and actually grasp the problem at hand (which I obviously dont). I stumbled across this while naively playing with C++ infinite ranges, starting with std::ranges::views::iota. So there I was, happily playing with signal generation, until I went stuck here: Modulating oscillation frequency while trying to stay stateless. But code says more then a foreign language, so: #!/usr/bin/env stack -- stack --resolver lts-19.8 runghc import Data.Ratio n = [0 ..] d = 10 -- EXAMPLE, usually 48000 t = (% d) <$> n sine f = (\x -> sin $ 2*pi * fromRational x * f x) <$> t sine1 = sine $ const 1 -- OK -- Lets devise a method to specify a value changing over time data I = No | Lin | Exp erp No a _ _ = a erp Lin a b mu = (1 - mu) * a + mu * b erp Exp a b mu = a * ((b / a) ** mu) data Curve a = Curve a [(I, Double, a)] at (Curve p1 []) _ = p1 at (Curve p1 ((i, d, p2):xs)) t = go 0 d p1 p2 i d xs where go t1 t2 p1 p2 i d xs | t < t2 = erp i p1 p2 $ (t - t1) / d | null xs = p1 | (i', d', p2') <- head xs = go t2 (t2 + d') p2 p2' i' d' $ tail xs -- Frequency modulation? c = Curve 1 [(Exp, 1.0, 2), (Exp, 1.0, 1)] sine2 = sine $ at c . fromRational -- WRONG!🙅 -- Whenever a change occurs, phase is incorrect -- because current step doesn't know about the past main = do print $ take 10 $ sine1 print $ at c 0.5 == at c 1.5 print $ take 10 $ sine2 -- The naive question of an experimenting non-math coder person is: -- Can a version of `at` be written which compensates for the phase -- differences which runs in O(n) where n is the number of curve points? -- Intuitively this should be possible given `d` (denominator). at' :: Curve a -> Ratio b -> a at' c t = undefined -- CYa, ⡍⠁⠗⠊⠕

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Dashboard
by Anton Pichugin 08 Jun '22

08 Jun '22

Hello everyone in the Haskell cafe! Such a nice place! My name is Anton. A month ago I started learning Haskell. I want to make a dashboard about the language. What data should I analyze and add to it? I see this project as a page where you can see charts and diagrams that change in real time. As of now I only have Google Trends (search Interest over time) + number of commits on GitHub. What else can I visualize? Which one could be helpful to the community? Kind regards, Anton Pichugin

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