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

30 Nov '23

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

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Mutual scoping question
by Todd Wilson 28 Nov '23

28 Nov '23

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

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

27 Nov '23

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

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

23 Nov '23

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

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

23 Nov '23

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

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A question about type families conflicting instances
by Darryn 22 Nov '23

22 Nov '23

Sir/Madam, I have familiarity with Haskell and have recently returned to using it on a small project, and have just taken a crack at using type families for the first time. I've used functional dependencies more in the past. My example below is a greatly simplified version of what I'm trying to do; for context, the overall purpose is a clean representation of logical forms across languages for abstract case analysis for theorem-proving for certain multimodal logics. The idea represented here is a unified representation for sentential forms and labelled sentential forms. The instance for the latter would be defined in terms of the instance for the former, but to keep it as simple as possible, the snippet here just has a separate (nonsense) implementation of three functions f1,f2,f3 that represent the pattern. I understand that that I'm running into overlapping instances but am unsure about how to correct it, and I couldn't find anything to address this in a search of the haskell-cafe archive (which is not to say that it isn't there, just that I couldn't find and/or recognise it). I'm sure it will be a simple matter to point me in the right direction here for people with more experience. Thank you to anyone in advance who can help; I do really appreciate it. ------------------------------------------------------------------------------- {-# LANGUAGE TypeFamilies, TypeFamilyDependencies, MultiParamTypeClasses, FlexibleInstances #-} -- A simplified model for sentences. data S a = SA a (S a) | SB a (S a) | SC String deriving (Eq, Show) -- A simplified model for what will be abstract case analysis: data Form a b = FA a b | FB deriving (Eq, Show) -- A simplified a model for the case analysis class: class (F a ~ b) => Formable a b where type F a = t | t -> a f1 :: b -> Form a b f2 :: b -> b f3 :: b -> Bool -- Simple test instance of Formable for S: instance Formable a (S a) where type F a = S a f1 (SA a y) = FA a y f1 (SB a y) = FA a y f1 (SC x) = FB f2 (SA a y) = SA a y f2 (SB a y) = SA a y f2 (SC x) = SC "nothing" f3 (SA a y) = False f3 (SB a y) = False f3 (SC _) = True -- Some test instances all work fine: -- > f1 (SA "a" (SB "b" (SC "c"))) -- > f2 (SA "a" (SB "b" (SC "c"))) -- > f3 (SA "a" (SB "b" (SC "c"))) -- A model of a wrapper for sentences to iadd integer labels: data W a = W Int (S a) deriving (Eq, Show) -- Test instance modelling an instance for labelled sentences: instance Formable a (W a) where type F a = W a f1 (W k (SA a y)) = FA a (W k y) f1 (W k (SB a y)) = FA a (W k y) f1 (W k (SC x)) = FB f2 (W k x) = W (1+k) x f3 (W k (SA a y)) = False f3 (W k (SB a y)) = False f3 (W k (SC _)) = True -- Intend to re-implement f1,f2,f3 in terms of the instance for S once -- I can convince GHC to let both instances stand. ------------------------------------------------------------------------------- Everything is dandy if either of the two instances, for S and for W, are provided, but GHC is not at all impressed with the idea of having both. GHCi reports the following error. Test.hs:29:10: error: Conflicting family instance declarations: F a = S a -- Defined at Test.hs:29:10 F a = W a -- Defined at Test.hs:51:10 Regards, D.

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Re: [Haskell-cafe] Haskell Usage
by Adrian Cochrane 16 Nov '23

16 Nov '23

Hi from New Zealand! My Haskell usage is more hobbyist than academic or industrial, but I've got a massive personal project written in Haskell (a browser engine). And I'm actively for one of my upcoming contracts (a converter between metadata formats) to use Haskell! I find I'm more productive in Haskell, and that my code is of generally higher quality. Its certainly not a popular language (neither is Erlang) though, which I have to actively plan for when suggesting it for a project. But given the dominance of C/C++, does that count for much? On 16/11/2023 1:00 am, haskell-cafe-request(a)haskell.org wrote: > Send Haskell-Cafe mailing list submissions to > haskell-cafe(a)haskell.org > > To subscribe or unsubscribe via the World Wide Web, visit > http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe > or, via email, send a message with subject or body 'help' to > haskell-cafe-request(a)haskell.org > > You can reach the person managing the list at > haskell-cafe-owner(a)haskell.org > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Haskell-Cafe digest..." > > > Today's Topics: > > 1. Haskell Usage (Henrique Caldeira) > 2. Re: Haskell Usage (Brandon Allbery) > 3. Re: Haskell Usage (Henning Thielemann) > 4. Re: Haskell Usage (Jo Durchholz) > 5. Re: Haskell Usage (MigMit) > 6. Re: Haskell Usage (Ivan Perez) > 7. Re: Haskell Usage (Jared Tobin) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Tue, 14 Nov 2023 21:27:57 +0000 (GMT+00:00) > From: Henrique Caldeira <h.caldeira(a)ua.pt> > To: haskell-cafe(a)haskell.org > Subject: [Haskell-cafe] Haskell Usage > Message-ID: <aae4e8e1-bf10-4bd5-bf58-9566b2a0be04(a)ua.pt> > Content-Type: text/plain; charset="utf-8" > > Good Evening from Portugal, > > I write to you about the usage of Haskell because I had a professor recommending me Erlang instead because Haskell was "more for academic purposes", which left me wondering if all my time spent was spent only for curiosity sake. > > I want to know how true my professor's statement is. > > I am very passionate about Haskell, although I admit the ecosystem can be confusing sometimes (for example, when to use cabal or stack, which versions of packages to use in order to avoid conflicts, or simply installing them through nixos or arch can be a learning process). > > Would love to hear your thoughts about all of this and thank you with all my heart. > > Lastly, all these wonderings are asked in a curious, "wanting to learn more" mindset. > > Kind regards, > Henrique Caldeira >

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How to use the GPU in Apple M2 from Haskell?
by David Banas 15 Nov '23

15 Nov '23

Does anyone have a good reference for explicitly accessing the GPU in the new Apple M2 chip from a user Haskell program?

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Re. Haskell Usage
by Rishiyur Nikhil 15 Nov '23

15 Nov '23

> Haskell was "more for academic purposes", The Bluespec Hardware Design Languages BSV (Bluespec SystemVerilog) and BH (Bluespec Haskell) digital hardware circuit design have been in industrial production and commercial use for over 20 years now. They have been used inside ST Micro, Texas Instruments, IBM, Qualcomm, Google, Galois and other companies, for ASIC and FPGA products and for high-level hardware prototyping and architecture exploration. The BSV and BH languages are themselves heavily inspired by Haskell. The 'bsc' compiler for BSV and BH is written entirely in Haskell, and has been in continuous use/development/maintenance/improvement for 20 years, and constitutes about 125K lines of Haskell. The 'bsc' compiler was open-sourced a few years ago and continues to be actively used and maintained: https://github.com/B-Lang-org/bsc The Haskell code for the compiler is in the src/ directory. Nikhil

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Haskell Usage
by Henrique Caldeira 15 Nov '23

15 Nov '23

Good Evening from Portugal, I write to you about the usage of Haskell because I had a professor recommending me Erlang instead because Haskell was "more for academic purposes", which left me wondering if all my time spent was spent only for curiosity sake. I want to know how true my professor's statement is. I am very passionate about Haskell, although I admit the ecosystem can be confusing sometimes (for example, when to use cabal or stack, which versions of packages to use in order to avoid conflicts, or simply installing them through nixos or arch can be a learning process). Would love to hear your thoughts about all of this and thank you with all my heart. Lastly, all these wonderings are asked in a curious, "wanting to learn more" mindset. Kind regards, Henrique Caldeira

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