- Haskell-Cafe - Haskell.org

Model beverage
by Daneel Yaitskov 04 Apr '22

04 Apr '22

Hi List, I came to Haskell from Java. At the beginning I was trying to map traditional notions of mainstream languages onto the FP world as “How to replace inheritance and late binding?”, etc. If Java developers drink coffee, then what is the model beverage for haskellers? “Psyllium Husk” fits the role, because besides phonetic similarities, the beverage is lazy (the recipe is simple - mix powder with water) and immutable (goes through the intestinal tract largely unaltered). Plus it is far off mainstream. -- Best regards, Daniil Iaitskov

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Default http2 library to use for client side?
by Ruben Astudillo 04 Apr '22

04 Apr '22

Hello Cafe I have been looking at hackage on what is the status for http2 **client** libraries. I haven't be able to grasp what is the default or recommended solution on this space. So far I have gotten the following impressions: 1. The usual candidates such as req / wreq libraries don't seem to support it. This is caused by they being based on `http-client`. 2. There is an http2-client [1] library that fits the bill. It uses Kazu's http2 [2] underneath, but it is upper bounded to major version 2 of that library. Kazu's library is now at major version 3 and it cannot be made to use the updated version easily. 3. Kazu's http2 library on major version 3 has a module called Network.HTTP2.Client which is even more low-level than what the previous option provided but it seems recently developed. It has a code sample. 4. Haskellers are not that interested on client side http2. I am no expert on this protocol, but it seems that there is some compatibility on it where you can make an http1.1 call and the server will handle it transparently (don't quote me on this). But Haskellers certainly were (are?) excited for http2 server support on warp which landed around 2015-2016. I have concluded that using `http2` [2] with the client module as my best bet. Is this analysis correct? or should I be looking a other packages that I haven't considered? Thanks for you time reading this email. [1]: <https://hackage.haskell.org/package/http2-client> [2]: <https://hackage.haskell.org/package/http2> -- Rubén. (pgp: 1E88 3AC4 89EB FA22)

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Re: [Haskell-cafe] Model beverage
by Olaf Klinke 03 Apr '22

03 Apr '22

>Well if that's the path we're going down, consider: > >Mushroom tea. > >It will take you outside of time, make you contemplate infinity, and take >your thoughts in abstract directions few other experiences can prepare >you >for; but in the end you come away surprisingly refreshed! > I'd rather reserve that one for dependently-typed languages. ;-) But it shows once more how biased we Europeans are towards alcoholic drugs. Olaf >On Sat, Apr 2, 2022, 9:00 AM Olaf Klinke <olf(a)aatal-apotheke.de> wrote: > >> Absinthe comes to mind. It is very potent, popular among >> philosophers but >> drives you crazy if consumed regularly, in large quantities.

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Fully Funded PhD Positions in the Safety and Security of Advanced Systems Group (Exeter, UK, Deadline 2022-04-29)
by Achim D. Brucker 03 Apr '22

03 Apr '22

We have two fully funded PhD scholarships for UK applicants in the Security and Trust of Advanced Systems Group [1] (Prof. Achim Brucker [2] and Dr. Diego Marmsoler [3]) at the Department of Computer Science of the University of Exeter, UK [4]. We are looking for enthusiastic and outstanding Computer Science or Mathematics students with a strong background in at least one of the following topics: * safety or security of (software) systems, * formal modelling or formal reasoning/verification, * program analysis or program verification, * language-based security, * semantics of programming languages, * theorem proving, model checking, * cryptographic protocols, * distributed systems (e.g., blockchain), * software security, * cyber-physical systems, * specification-based testing, and * design and implementation of security architectures. The positions offer the flexibility to define the PhD topic jointly between the successful candidate and the supervisors. Interested candidates should contact the potential supervisor Prof. Achim Brucker (a.brucker(a)exeter.ac.uk) or Dr. Diego Marmsoler (d.marmsoler(a)exeter.ac.uk) to discuss their application. For more details, please consult the official advertisements: * Compositional Verification of Smart Contracts in Isabelle: https://www.exeter.ac.uk/study/funding/award/?id=4326 * Formal Verification for Safety- or Security-Critical Systems: https://www.exeter.ac.uk/study/funding/award/?id=4328 The closing date for applications is midnight on the 29th April 2022. Best, Achim and Diego [1] http://emps.exeter.ac.uk/computer-science/research/cyber-security/ [2] https://www.brucker.ch/ [3] https://marmsoler.com/ [4] http://emps.exeter.ac.uk/computer-science/ -- Prof. Achim Brucker | Chair in Cybersecurity & Head of Group | University of Exeter https://www.brucker.ch | https://logicalhacking.com/blog @adbrucker | @logicalhacking

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Model beverage
by Olaf Klinke 03 Apr '22

03 Apr '22

> Hi List, > > I came to Haskell from Java. At the beginning I was trying to map > traditional notions of mainstream languages onto the FP world as “How to > replace inheritance and late binding?”, etc. > > If Java developers drink coffee, then what is the model beverage for > haskellers? > > “Psyllium Husk” fits the role, because besides phonetic similarities, the > beverage is lazy (the recipe is simple - mix powder with water) and > immutable (goes through the intestinal tract largely unaltered). Plus it is > far off mainstream. > > > -- > > Best regards, > Daniil Iaitskov Absinthe comes to mind. It is very potent, popular among philosophersbut drives you crazy if consumed regularly, in large quantities. Cheers, Olaf

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Can't use TypeApplications with polymorphic let bind
by Georgi Lyubenov 29 Mar '22

29 Mar '22

Dear Cafe, I recently came upon this little "type-inference puzzle". Can anyone shine some light on why the third example doesn't compile? ``` {-# LANGUAGE TypeApplications #-} -- doesn't work -- I expect this, not sure why it happens {- class C m where c :: () -> m instance C Int where c () = 0 instance C Bool where c () = False f :: (Int, Bool) f = let x = c in (x (), x ()) -} -- works -- I expect this, not sure why it happens {- class C m where c :: () -> m instance C Int where c () = 0 instance C Bool where c () = False f :: (Int, Bool) f = let x u = c u in (x (), x ()) -} -- doesn't work -- I don't expect this, not sure why it happens {- class C m where c :: () -> m instance C Int where c () = 0 instance C Bool where c () = False f :: (Int, Bool) f = let x u = c u in (x @Int (), x @Bool ()) -- wtf.hs:54:5: error: -- • Cannot apply expression of type ‘() -> m0’ -- to a visible type argument ‘Int’ -- • In the expression: x @Int () -- In the expression: (x @Int (), x @Bool ()) -- In the expression: let x u = c u in (x @Int (), x @Bool ()) -- | -- 54 | (x @Int (), x @Bool ()) -- | ^^^^^^^^^ -} ``` Cheers, Georgi

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New Executive Director for the Haskell Foundation
by Richard Eisenberg 29 Mar '22

29 Mar '22

Official announcement on Discourse: https://discourse.haskell.org/t/new-executive-director-for-the-haskell-foun… <https://discourse.haskell.org/t/new-executive-director-for-the-haskell-foun…> Text repeated here (but responses from David and Andrew are already on Discourse): It is my great pleasure to announce the next Executive Director of the Haskell Foundation: David Thrane Christiansen. David is a long-time Haskeller who comes with a demonstrated passion for functional programming, having done intensive work with Idris, Racket, and Haskell, among other formative experiences. In particular, David was a key part of the Idris community when it morphed from a smallish language project to one more widely used. David holds a PhD in Computer Science from the IT University of Copenhagen (the city where he currently lives), has co-authored a book on dependent types (The Little Typer), and has worked for Galois and Deon Digital. Lest anyone get worried about one PhD excited about dependent types (me) involved in hiring another PhD excited about dependent types (David): over the course of many conversations about the HF, David has impressed upon me the importance of reaching out beyond current Haskell communities, seeking new voices and approaches. Haskell is a language that anyone can master -- but we have work to do to have its perception match that reality. I know David is committed to that course of action, and of focusing on the practical aspects of Haskell use that affect the Haskell community broadly. David begins his employment with the HF on Monday, May 2. About the process: The HF formed a Transition Committee (our charter is public: https://gitlab.haskell.org/hf/meta/-/blob/main/committees/transition.md) comprising José Pedro Magalhães (chair), Ed Kmett, and myself. We put together a call for applications and processed these applications as they came in. Applicants that passed an initial screening interview were given four additional interviews. The Transition Committee then made a recommendation to the Board based on the written feedback from these interviews, and the Board voted unanimously and enthusiastically to accept the recommendation to hire David. I hope you join me in being excited about this next chapter for the Haskell Foundation! Richard

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First CfP: FMBC 2022 - 4th International Workshop on Formal Methods for Blockchains
by Zaynah Dargaye 29 Mar '22

29 Mar '22

FMBC 2022 First Call for Papers [ Please distribute, apologies for multiple postings. ] ======================================================================== 4th International Workshop on Formal Methods for Blockchains (FMBC) - First Call https://fmbc.gitlab.io/2022 August 11, 2022, Haifa, Israel Co-located with the The Federated Logic Conference 2022 (FLoC 22 -- https://www.floc2022.org/) as a satellite workshop of the 34th International Conference on Computer-Aided Verification (CAV 2022 -- http://i-cav.org/2022/) ----------------------------------------------------------------- Important dates --------------------- Abstract submission: May 3, 2022 Full paper submission: May 10, 2022 Notification: June 15, 2022 Camera-ready: July 13, 2022 Workshop: August 11, 2022 Deadlines are Anywhere on Earth -- https://en.wikipedia.org/wiki/Anywhere_on_Earth. ---------------------- ---------------------- TOPICS OF INTEREST --------------------- Blockchains are decentralized transactional ledgers that rely on cryptographic hash functions for guaranteeing the integrity of the stored data. Participants on the network reach agreement on what valid transactions are through consensus algorithms. Blockchains may also provide support for Smart Contracts. Smart Contracts are scripts of an ad-hoc programming language that are stored in the Blockchain and that run on the network. They can interact with the ledger’s data and update its state. These scripts can express the logic of possibly complex contracts between users of the Blockchain. Thus, Smart Contracts can facilitate the economic activity of Blockchain participants. With the emergence and increasing popularity of cryptocurrencies such as Bitcoin and Ethereum, it is now of utmost importance to have strong guarantees of the behavior of Blockchain software. These guarantees can be brought by using Formal Methods. Indeed, Blockchain software encompasses many topics of computer science where using Formal Methods techniques and tools are relevant: consensus algorithms to ensure the liveness and the security of the data on the chain, programming languages specifically designed to write Smart Contracts, cryptographic protocols, such as zero-knowledge proofs, used to ensure privacy, etc. This workshop is a forum to identify theoretical and practical approaches of formal methods for Blockchain technology. Topics include, but are not limited to: * Formal models of Blockchain applications or concepts * Formal methods for consensus protocols * Formal methods for Blockchain-specific cryptographic primitives or protocols * Design and implementation of Smart Contract languages * Verification of Smart Contracts ---------------------- ---------------------- SUBMISSION --------------------- Submit original manuscripts (not published or considered elsewhere) with a page limit of 12 pages for full papers and Systematization of Knowledge (SoK) papers, 6 pages for short papers, and 2 pages for tool papers (excluding bibliography and short appendix of up to 5 additional pages). Alternatively, you may also submit an extended abstract of up to 3 pages (including a bibliography) summarizing your ongoing work in the area of formal methods and blockchain. Authors of selected extended abstracts are invited to give a short lightning talk. -------------------- -------------------- PROCEEDINGS ------------------- All submissions will be peer-reviewed by at least three members of the program committee for quality and relevance. Accepted regular papers (full and short papers) will be included in the workshop proceedings. ---------------------- ---------------------- INVITED SPEAKER --------------------- Massimo Bartoletti, Professor, Università degli Studi di Cagliari, Italy ---------------------- ---------------------- PROGRAM COMMITTEE --------------------- PC CO-CHAIRS * Zaynah Dargaye (Nomadic Labs, France) (zaynah.dargaye(a)nomadic-labs.com) * Schneidewind Clara, (MPI-SP, Germany) (clara.schneidewind(a)mpi-sp.org) PC MEMBERS Wolfgang Ahrendt (Chalmers University of Technology, Sweden) Leonardo Alt (Ethereum Foundation, Germany) Lacramioara Astefanoaei (Nomadic Labs, France) Roberto Blanco (MPI-SP, Germany) Joachim Breitner (Germany) Achim Brucker (University of Exeter, UK) Ethan Cecchetti (University of Maryland, USA) Manuel Chakravarty (IOHK & Tweag, Netherlands) Jing Chen (Algorand Inc, USA) Jérémie Decouchant (TU Delft, Netherlands) Antonella Del Pozzo (Université Paris-Saclay & CEA & List, France) Dana Drachsler Cohen (Technion, Israel) Cezara Dragoi (INRIA & ENS & CNRS & PSL, France) Ansgar Fehnker (Twente, Netherlands) Dominik Harz (Interlay & Imperial College London, UK) Lars Hupel (INNOQ, Germany) Igor Konnov (Informal Systems, Austria) Paul Laforgue (Nomadic Labs, France) Julian Nagele (Bank of America, USA) Russel O’Connor (Blockstream) Maria Potop-Butucaru (LIP6, France) Albert Rubio (Complutense University of Madrid, Spain) César Sanchez (IMDEA, Spain) Sun Meng (Peking University, China) Simon Thompson (IO Global, UK) Josef Widder (Informal Systems, Austria)

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[ANN] base16-0.3.2.0, base32-0.2.2.0, base64-0.4.2.4
by Emily Pillmore 29 Mar '22

29 Mar '22

Hello All, I'm pleased to announce that `base16`, `base32`, and `base64` have been updated to support GHC 9.2.x. In the most recent versions, due to GHC issue #20338 in which `targetByteOrder` was incorrect on Big Endian architectures, the required GHC version lower bound has been upped to GHC 8.10.x. In this version, GHC 8.10.x was silently patched to fix this behavior. Cheers, Emily

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inference with implicitparams seems broken
by rowan goemans 28 Mar '22

28 Mar '22

Hello everyone, I wonder why the following taken from an stackoverflow answer doesn't work: https://stackoverflow.com/questions/71184922/is-it-possible-to-infer-a-type…. Code of the answer posted here verbatim: ``` {-# LANGUAGE ImplicitParams #-} {-# LANGUAGE RankNTypes #-} module Temp where withX :: Int -> ((?x :: Int) => r) -> r withX x r = let ?x = x in r somethingThanNeedsX :: (?x :: Int) => Int somethingThanNeedsX = ?x + 2 foo :: Int foo = bar where bar = withX 42 baz baz = somethingThanNeedsX ``` This won't compile with the error message: ``` Orig.hs:19:11: error: • Unbound implicit parameter (?x::Int) arising from a use of ‘somethingThanNeedsX’ • In the expression: somethingThanNeedsX In an equation for ‘baz’: baz = somethingThanNeedsX In an equation for ‘foo’: foo = bar where bar = withX 42 baz baz = somethingThanNeedsX | 19 | baz = somethingThanNeedsX ``` If you give `baz` a type signature which includes the implicit param it compiles. But I think this is a bug. GHC should not require a type signature here. I tried searching for a GHC ticket but I couldn't find one. But that might also be down to me not using the right query. Anyway my question is, is this expected behavior? This really makes implicit params less ergonomic. Best regards, Rowan Goemans

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