- Haskell-Cafe - Haskell.org

Which gogol-* library provides access to the "secrets manager" API on cloud run?
by Ruben Astudillo 17 Feb '22

17 Feb '22

Hello -Cafe On the company I work for we are migrating to google cloud run. As part of the migration I have to interface with the secret management API[1]. I got the `gogol`[2] library compiling and working, yet I don't seem to find a package nor module what provides this functionality. Is this supported by the `gogol` library? Am I not looking at the correct sub-package? Any direction, alternatives or feedback are appreciated. [1]: <https://cloud.google.com/secret-manager/docs/reference/libraries> [2]: <https://github.com/brendanhay/gogol> -- Rubén. (pgp: 1E88 3AC4 89EB FA22)

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Several Haskell roles with Core Strats at Standard Chartered
by José Pedro Magalhães 13 Feb '22

13 Feb '22

Full details here (so I can update the Shanghai link once it's up): https://discourse.haskell.org/t/several-haskell-roles-with-core-strats-at-s… Cheers, Pedro

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Any chances to fetch data from Vertica DB?
by Geraldus 11 Feb '22

11 Feb '22

Hi, dear Café! I'm trying to figure out if there is any way to connect and fetch data from the Vertica database? I got used to the amazing `esqueleto` package, and ideally, I'm looking for a way to use type-safe queries. Albeit at the moment raw SQL queries would be sufficient. Any feedback would be appreciated!

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C binding <-> safer haskell API
by PICCA Frederic-Emmanuel 10 Feb '22

10 Feb '22

Hello, I try to create a binding for a C library I can find something like this in the c library merge(HklCube *cube, const HklFrame *frame) So I create a binding with binding-DSL #ccall merge, Ptr <HklCube> -> Ptr <HklFrame> -> IO () Now I want to create a higher level API whcich encode the fact that the cube is modified after the merge. So what is the best way to encode this in the type ? merge :: _ merge c f = do .... c'merge pc pf I thought about IORef, but I am not sure thaht this is the right way to have a safer haskell interface for this method. thanks for your help Fred

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Haskell Foundation Stability Working Group
by Chris Dornan 10 Feb '22

10 Feb '22

Hi Everyone, This is to announce the formation of the Haskell Foundation Stability Working Group <https://github.com/haskellfoundation/stability>, a new working group for for studying and promoting stability in the Haskell ecosystem. Check out our our home page <https://github.com/haskellfoundation/stability> (https://github.com/haskellfoundation/stability) where you can read about who we are, and what we do and are doing (and have been doing). We meet on a call about once a fortnight – let us know if you would like to join any of our calls or raise any topic with the group (the e-list for contacting the group is on the home page). Chris Dornan for the Haskell Foundation Stability Working Group

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current status of cloud haskell?
by stuebinm 09 Feb '22

09 Feb '22

Hi all! I've been meaning to do more with concurrent (and parallel) haskell, and having looked around a bit on hackage (and being a fan of Erlang's OTP) the cloud haskell packages seem like a dream come true. But only at first glance — the last release of distributed-process [1], which looks to be the main library, was in 2018, and many of the other packages are older. The "recent news" section of the website [2] even has its last entry from 2016! So I'd be assuming that the project has been abandoned, yet on github [3] it looks to still be (comparatively) alive and well, with activity just a few months ago. So what's the current status there? Is anyone here using it productively, or involved in its development / knows if or when to expect a new release? thanks! ~stuebinm [1] https://hackage.haskell.org/package/distributed-process [2] http://haskell-distributed.github.io/ [3] https://github.com/haskell-distributed/distributed-process

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Haskell Foundation seeks new Executive Director
by Richard Eisenberg 09 Feb '22

09 Feb '22

Hi all, Following Andrew Boardman's resignation announcement [1] yesterday, the Haskell Foundation is seeking a new Executive Director. The job ad appears below. Note that we are eager to identify our next leader, and so the turnaround is tight -- we will fully consider only applications received by the end of Feb 22 (anywhere on Earth). Please spread the word, recommend folks to consider, use your networks, etc! Feel free to post here or reach out to me with any questions. Job ad home: https://haskell.foundation/careers/ed.html [1]: https://discourse.haskell.org/t/haskell-foundation-executive-director-chang… ------------------------------ # Executive Director ## About the Haskell Foundation The Haskell Foundation (HF) is an independent, non-profit organization dedicated to broadening the adoption of Haskell, by supporting its ecosystem of tools, libraries, education, and research. ## The Role HF seeks a full-time Executive Director (ED) to continue to inspire and develop the organization. The ED is responsible for furthering HF’s mission and vision, ensuring that resources are in place to accomplish its goals. The ED will drive sourcing for sponsorships, structure the organization, recruit and channel the efforts of both volunteers and paid staff. Working with HF's Board of Directors, the ED will articulate HF’s strategic priorities and direction. They will assess and evaluate strategies, hire teams, set budgets, forge alliances, and build partnerships to further the mission. The ED will play a crucial role in building the culture of HF around community service. HF will succeed if and only if it succeeds in unlocking the expertise and enthusiasm of volunteer members of the community. This will be a major goal for the ED, so that volunteers find HF to be a solid professional home with ample opportunities for recognition and professional growth. Finally, the ED will actively promote HF to build its financial reserves and goodwill. They will secure, budget, and allocate resources appropriately and hold themselves accountable for the financial health of the organization. ## Reporting Relationships The ED reports to the Board of Directors. All other members of staff and volunteers report directly or indirectly to the ED. ## Responsibilities **Organization Mission and Strategy**: Works with the Board and staff to ensure that the mission is fulfilled. * Responsible for the implementation of volunteer programs that carry out the organization’s mission. * Responsible for recruiting existing community projects to affiliate with HF, and for assessing their ongoing adherence to HF standards. * Responsible for the enhancement of HF’s image by being engaged with the community and by working closely with other professional and private organizations. * Be the public face of HF through public presentations at Haskell-related events. * Cultivate excellent relationships with the community and operate HF’s social media presence. **Organization Operations**: Oversees and implements appropriate resources to ensure that the operations of the organization are appropriate. * Responsible for the hiring and retention of competent, qualified staff as financial resources permit. * Responsible for the effective administration of HF’s operations. * Responsible for signing all notes, agreements, and other instruments made and entered into and on behalf of the organization. * Responsible for fiscal management that generally anticipates operating within the approved budget, ensures maximum resource utilization, and maintenance of the organization in a positive financial position. **Viability**: Develops financial resources sufficient to ensure the sustainability of the organization. * Responsible for fundraising and developing other revenues necessary to support HF’s mission. * Participate in identifying and cultivating corporate, institutional and individual sponsors. **Board Governance**: Works with the Board to help it enact HF’s mission. * Responsible for leading HF in a manner that supports the organization’s mission. * Responsible for communicating effectively with the Board and providing, in a timely and accurate manner, all information necessary for the Board to function properly and to make informed judgements. * Ensure that HF is in compliance with relevant state and federal laws, regulations and with standard accounting procedures. * Work with individual Board members and subcommittees as directed by the Board. * Inform the Board regularly of internal organization matters, including relevant staffing, funding and program success and priorities. * Responsible for the fiscal integrity of HF, ensure that the Board is able to monitor the financial condition of HF. This means preparing budgets and financial statements which accurately reflect the financial condition of the organization and are kept up to date. ## Salary and Employment The ED can live anywhere in the world – remote working is the standard within HF. The ED must be eligible under USA law and the law in their jurisdiction to perform work (as an employee or as a contractor) for a non-profit organization incorporated in the USA. Salary will be commensurate with the experience and qualities of the candidate, and will also reflect the Foundation’s status as a non-profit organization funded by donations. ## Key Credentials and Personal Qualities Candidates are encouraged to apply with the expectation that the Board will assist and coach in areas of personal development tailored to the successful candidate’s needs. **Essential attributes:** * Successful experience in development and organizational leadership in a non-profit or business setting. * Self-starter, with strong motivational and staff leadership abilities. * Demonstrated knowledge, via experience or an advanced degree in CS, math or a related technical field. * Willingness to execute fundraising plans and strategies that generate significant results. * Commitment to results; “can-do" mindset with emphasis on accountability. * Exceptional in communicating verbally and in written language. * Integrity and impeccable work ethic. **Desirable attributes:** * Experience at change management. * Experience in writing persuasive materials including successful appeals, proposals, presentations, stewardship materials, and other collateral. * Knowledge of the Haskell community and its dynamics. HF celebrates diversity and inclusion, and does not discriminate on an individual’s identity characteristics. Under-represented minorities are especially encouraged to apply. ## Application Process Interested candidates should submit a resume and thoughtful cover letter outlining how their skills and experience meet the qualifications of the position, and their vision for the Foundation. Send to nominations(a)haskell.foundation. If you have any questions about the position, feel free to email chair(a)haskell.foundation. Closing date: Tuesday, February 22, 2022.

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Re: [Haskell-cafe] optparse-applicative with attoparsec parser
by Sébastien Leblanc 07 Feb '22

07 Feb '22

> > Date: Fri, 4 Feb 2022 15:09:41 +0100 (CET) > From: PICCA Frederic-Emmanuel > <frederic-emmanuel.picca(a)synchrotron-soleil.fr> > To: haskell-cafe(a)haskell.org > Subject: [Haskell-cafe] optparse-applicative with attoparsec parser > Message-ID: > < > 30404406.15581346.1643983781075.JavaMail.zimbra(a)synchrotron-soleil.fr> > > Content-Type: text/plain; charset=utf-8 > > Hello, > > I Try to write a parser for this command line > > binoculars-ng --debug process data/test/config_sixs_ruche_flymedv_3.ini > 698-734 735-736 > > But I have this problem > > Invalid argument `735-736' > > The parser used for this is this one > > processOptions :: Parser Options > processOptions = Process > <$> optional config > <*> optional (argument (eitherReader (parseOnly > configRangeP . pack)) (metavar "RANGE")) > > it use the configRangeP attoparser parser whcih knows how to deal with the > string "698-734 735-736" > > configRangeP :: Parser ConfigRange > configRangeP = ConfigRange <$> (inputRangeP `sepBy` many (satisfy isSep)) > where > isSep :: Char -> Bool > isSep c = c == ' ' || c == ',' > > the result should be this one > > Just (ConfigRange [InputRangeFromTo 698 734,InputRangeFromTo 735 736]) > > so my question how should I fix my processOptions fucntion in order to > deal with this problem. > > thanks for considering > It seems that the issue stems from having your arguments separated by spaces. If your parser is parsing [[ [debug-flag] <command> <file> <ranges> ]], then it does not know what to do with the last particle (735-736). You would need to wrap your ranges in quotes in your shell, to include the space, or replace the space with a comma instead (698-734,735-736) Sébastien

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Haskell Developer Roles at Standard Chartered Bank (UK and SG)
by J. Stutterheim 07 Feb '22

07 Feb '22

Hi all, I'm happy to report that my team at Standard Chartered Bank is hiring Haskell programmers! We're currently hiring in London, and we expect to open positions in Singapore soon. If you're interested in writing Haskell code for mission-critical cloud-based applications, this is the job for you. Financial knowledge is not required, as there will be plenty of opportunity to pick it up on the job. If you're interested in having a chat, please apply through the following link: https://scb.taleo.net/careersection/ex/jobdetail.ftl?job=2200001642&lang=en After applying through the link above, please shoot me an email at `jurrien dot stutterheim at sc dot com` so that I know that you have applied. Best regards, Jurriën

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How can I get a list of all English words?
by Amber Crawford 06 Feb '22

06 Feb '22

I'm creating a project in which I need a list of every English word, so I'm wondering how I would get this. The only thing I need is that I can filter the words based on some boolean function, thanks. btw I'm pretty beginner so sry If i'm not really good at writing these.

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optparse-applicative with attoparsec parser
by PICCA Frederic-Emmanuel 04 Feb '22

04 Feb '22

Hello, I Try to write a parser for this command line binoculars-ng --debug process data/test/config_sixs_ruche_flymedv_3.ini 698-734 735-736 But I have this problem Invalid argument `735-736' The parser used for this is this one processOptions :: Parser Options processOptions = Process <$> optional config <*> optional (argument (eitherReader (parseOnly configRangeP . pack)) (metavar "RANGE")) it use the configRangeP attoparser parser whcih knows how to deal with the string "698-734 735-736" configRangeP :: Parser ConfigRange configRangeP = ConfigRange <$> (inputRangeP `sepBy` many (satisfy isSep)) where isSep :: Char -> Bool isSep c = c == ' ' || c == ',' the result should be this one Just (ConfigRange [InputRangeFromTo 698 734,InputRangeFromTo 735 736]) so my question how should I fix my processOptions fucntion in order to deal with this problem. thanks for considering Frederic

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Asking for advice on category for a paper for ICFP
by Anton Kholomiov 02 Feb '22

02 Feb '22

Hi! I'm trying to write a paper for ICFP, This is my first paper of this kind. Can you please help me to choose the right category for it? The paper is about a novel technique of implementation of FRP. I've studied the Haskell FRP zoo and I can confirm that it's novel. In my opinion it's very elegant and simple, but of course I'm biased :) So far so good. Can you please help me to choose the right category for it? Is it a normal research paper or is it a functional pearl? So the FRP is an old technique, but I propose a novel variant of implementation which I hope is easy to study even in normal class rooms and does not contain unsafePerform tricks. Cheers, Anton

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[ANN] opc-xml-da-client, a client for the OPC XML-DA protocol
by Olaf Klinke 31 Jan '22

31 Jan '22

Dear Haskell Café, I am pleased to announce opc-xml-da-client [1,2], an implementation of (the client side of) the OPC XML-DA data access protocol. While the OPC XML-DA protocol is quite dated (2003) and has largely been superseded by other OPC flavours, it is still being used in industrial environments. OPC XML-DA is based on SOAP and the data types in the Haskell package closely reflect the protocol specification as a web services description language document [5]. This package was developed by Mlabs [3] as contract work for my employer. We release it as FOSS, with Mlabs kindly hosting the project under their Github account. To my knowledge, besides PyOPC [4] this is the only freely available OPC XML-DA library and the only Haskell OPC library. We stopped using PyOPC because Python hit performance limits while parsing the XML. Feel free to contact me or Nikita Volkov at Mlabs if you have further questions. Cheers Olaf [1] https://github.com/mlabs-haskell/opc-xml-da-client [2] https://hackage.haskell.org/package/opc-xml-da-client [3] https://mlabs.city [4] https://pypi.org/project/PyOPC/ [5] https://opcfoundation.org/XMLDA/1.0/OpcXmlDa1.00.wsdl

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how to set extra-lib-dirs for a dependency in a stack project?
by Johannes Waldmann 30 Jan '22

30 Jan '22

Dear Cafe, is it possible to specify include-dirs and extra-lib-dirs for a dependency? I have * top-level project A, depends on: * project B, depends on: * C: external library (written in C) I am building A with stack. I don't want to put fixed locations (include/lib) for C in B.cabal, because it depends on the (top-level) build environment of A (e.g., my machine, or CI). Concrete example: C = kissat SAT solver, B = Haskell API for C. I know that, e.g., https://hackage.haskell.org/package/minisat works around this problem by vendoring (is this the word?) the solver's code (into B). I don't want this. With cabal.project, I could set options for (all?) dependencies? https://cabal.readthedocs.io/en/3.4/cabal-project.html#foreign-function-int… Would stack use this setting (will it read that file at all)? Will I have to copy all extra-deps source repo locations to cabal.project? - J.

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Some Love for wxHaskell
by Tilmann 30 Jan '22

30 Jan '22

Hi cafe, I think wxHaskell needs some love :) Over the years I've written a small client for FICS (Free Internet Chess Server) and wxHaskell has served me really well. Also, wxWidgets seems solid and alive.. but today, wxHaskell is lagging behind updates and seems *sniff* dead. Is someone working on wxHaskell atm? I'd love to connect and help. If not, is there some interest to rejuvenate wxHaskell? Who is also depending on wxHaskell and wants to keep it going? Or, is it time to move on to gtk or reflex? Very much looking forward to your replies! Best, Tilmann

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Coercing existential according to type-level Maybe (re-post from h-beginners)
by Dmitriy Matrosov 29 Jan '22

29 Jan '22

(as suggested, i'm re-asking here) Hi. I've tried to write a function to coerce existential value according to type stored in type-level 'Maybe' (i.e. 'Just or 'Nothing). > {-# LANGUAGE DataKinds #-} > {-# LANGUAGE RankNTypes #-} > {-# LANGUAGE KindSignatures #-} > {-# LANGUAGE PolyKinds #-} > {-# LANGUAGE TypeFamilies #-} > {-# LANGUAGE GADTs #-} > > import Data.Kind > import Data.Proxy > import Unsafe.Coerce > > class FromTypeMaybe k where > type ToType k > fromTypeMaybe :: (a -> ToType k) -> Proxy k -> a -> Maybe (ToType k) > > --instance forall (t :: Type). FromTypeMaybe ('Nothing :: Maybe t) where > instance forall (t :: Type). FromTypeMaybe ('Nothing @t) where > type ToType 'Nothing = t > fromTypeMaybe f _ x = Nothing > > instance forall (t :: Type). FromTypeMaybe ('Just t :: Maybe Type) where > type ToType ('Just t) = t > fromTypeMaybe f _ x = Just (f x) > > data Any where > Any :: a -> Any > > unAny :: Any -> t > unAny (Any x) = unsafeCoerce x This works as far as i can see *Main> fromTypeMaybe unAny (Proxy @('Just Int)) (Any 3) Just 3 *Main> fromTypeMaybe unAny (Proxy @'Nothing) undefined Nothing but i don't understand how 'Nothing instance works: type kind kind? vvv vvvvvv vvv instance forall (t :: Type). FromTypeMaybe ('Nothing :: Maybe t) where type ToType 'Nothing = t ^^^ type (in case alignment breaks: variable 't' in forall is type-variable with kind 'Type', but in "Maybe t" in instance head it's used as kind-variable. And then in associated type-family the same variable 't' is used as type-variable again). If i try to write "'Nothing"'s kind as 'Maybe Type' (in the same manner as 'Just has) instance forall (t :: Type). FromTypeMaybe ('Nothing :: Maybe Type) where i get an error: 1.lhs:21:3: error: • Type variable ‘t’ is mentioned in the RHS, but not bound on the LHS of the family instance • In the type instance declaration for ‘ToType’ In the instance declaration for ‘FromTypeMaybe ('Nothing :: Maybe Type)’ | 21 | > instance forall (t :: Type). FromTypeMaybe ('Nothing :: Maybe Type) where | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^... Well, i'm not sure, that understand why 'forall' in instance head may not be used as family's LHS, but.. that's another question. On the other hand, if i try to write 'Just instance using type-variable 't' as kind-variable (in the same manner as 'Nothing has): instance forall (t :: Type). FromTypeMaybe ('Just t :: Maybe t) where i get an error too: 1.lhs:25:47: error: • Expected kind ‘Maybe t’, but ‘'Just t’ has kind ‘Maybe *’ • In the first argument of ‘FromTypeMaybe’, namely ‘('Just t :: Maybe t)’ In the instance declaration for ‘FromTypeMaybe ('Just t :: Maybe t)’ | 25 | > instance forall (t :: Type). FromTypeMaybe ('Just t :: Maybe t) where Well, that's also probably expected, because though i've declared type-variable 't' with kind 'Type' in forall, due to 'DataKinds' extension type 't' is also promoted to kind 't' and, thus, by using ('Just t :: Maybe t) i say, that ('Just t) should have kind 'Maybe t', not 'Maybe Type', which it really has. But if that's so, how working 'Nothing instance instance forall (t :: Type). FromTypeMaybe ('Nothing :: Maybe t) where may work at all? It has the same problem as 'Just instance above: type-variable 't' is promoted to kind 't' and 'Nothing will have kind 'Maybe t' instead of 'Maybe Type' ?

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Request for Nominations to the GHC Steering Committee
by Joachim Breitner 29 Jan '22

29 Jan '22

Dear Haskell community, the GHC Steering committee is seeking nominations for at least two new members. The committee scrutinizes, nitpicks, improves, weights and eventually accepts or rejects proposals that extend or change the language supported by GHC and other (public-facing) aspects of GHC. Our processes are described at https://github.com/ghc-proposals/ghc-proposals which is also the GitHub repository where proposals are proposed. In particular, please have a look at the bylaws at https://github.com/ghc-proposals/ghc-proposals/blob/master/committee.rst We are looking for a member who has the ability * to understand such language extension proposals, * to find holes and missing corner cases in the specifications, * foresee the interaction with other language features and specifications, * comment constructively and improve the proposals, * judge the cost/benefit ratio and * finally come to a justifiable conclusion. We look for committee members who have some of these properties: * have substantial experience in writing Haskell applications or libraries, which they can use to inform judgements about the utility or otherwise of proposed features, * have made active contributions to the Haskell community, for some time, * have expertise in language design and implementation, in either Haskell or related languages, which they can share with us. The committee’s work requires a small, but non-trivial amount of time, especially when you are assigned a proposal for shepherding. We estimate the workload to be around 2 hours per week, and our process works best if members usually respond to technical emails within 1-2 weeks (within days is even better). Please keep that in mind if your email inbox is already overflowing. There is no shortage of people who are eager to get fancy new features into the language, both in the committee and the wider community. But each new feature imposes a cost, to implement, to learn, (particularly) through its unexpected interaction with other features. We need to strike a balance, one that encourages innovation (as GHC always has) while still making Haskell attractive for real-world production use and for teaching. We therefore explicitly invite “conservative” members of the community to join the committee. To make a nomination, please send an email to me (as the committee secretary) at mail(a)joachim-breitner.de until February 11th. I will distribute the nominations among the committee, and we will keep the nominations and our deliberations private. We explicitly encourage self-nominations. You can nominate others, but please obtain their explicit consent to do so. (We don’t want to choose someone who turns out to be unable to serve.) On behalf of the committee, Joachim Breitner -- Joachim Breitner mail(a)joachim-breitner.de http://www.joachim-breitner.de/

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[ANN]: traverse-code
by David Feuer 28 Jan '22

28 Jan '22

I've put up a tiny little package[1], traverse-code, offering a generic way to "traverse" in Template Haskell's `Code m`. class TraverseCode t where traverseCode :: Quote m => (a -> Code m b) -> t a -> Code m (t b) I wrote this primarily as a way to "lift" operations on polymorphic data structures into Template Haskell. For example, for Data.Sequence, you can write triple :: a -> a -> a -> Seq a triple a b c = $$(sequenceCode $ fromList [ [||a||], [||b||], [||c||] ]) The `triple` function will not form its arguments into a list and then convert it to a sequence; rather, it will build the result sequence directly, using the underlying constructors. A generic default definition is available for all instances of Generics.Linear.Generic1. See linear-generics[2] for information about how to derive those. There's nothing particularly linear about traverse-code, but linear-generics has a more general Generic1 than GHC.Generics offers. [1] https://hackage.haskell.org/package/traverse-code [2] https://hackage.haskell.org/package/linear-generics

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Munich Virtual Haskell Meeting, 2022-01-31 @ 19:30
by Leah Neukirchen 28 Jan '22

28 Jan '22

Dear all, Next week, our monthly Munich Haskell Meeting will take place again on Monday, January 31 on Jitsi at 19:30 CEST. **Due to the pandemic, this meeting will take place online!** For details see here: https://muenchen.haskell.bayern/dates.html A Jitsi link to join the room is provided on the page. Everybody is welcome, especially the Haskellers from Bavaria that do not usually come to our Munich meetings due to travel distance! cu, -- Leah Neukirchen <leah(a)vuxu.org> https://leahneukirchen.org/

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Question about ambiguity and defaulting in recursive bindings
by Benjamin Redelings 26 Jan '22

26 Jan '22

Hi, I am trying to understand how GHC treats the following declaration. f c i = if i == 10 then c else g c 'b' g 'a' w = f 'b' 10 g z w = z l = (f 'a' (1::Int), f 'a' (1.0::Double)) It seems to me like, after defaulting, f should have the following type: Char -> Int -> Char However, looking at -ddump-tc, GHC is deriving the polymorphic type forall a. (Eq a, Num a) => Char -> a -> Char That's much nicer, because its more flexible. But I'm confused, because it looks like GHC is defaulting 'g', but not 'f', even though they are in the same recursive group. This seems to contradict "Typing Haskell in Haskell", which is what I am looking at right now. If that is correct, can anybody point me to a paper or documentation about how this works? More detail: 1. If I understand correctly, the definitions of `f` and `g` are mutually recursive, and should be typed together, and the declaration group is not restricted. 2. It seems like, before generalization, we have f :: Char -> a -> Char g :: Char -> Char -> Char Predicates include (Eq a, Num a) 3. Looking at the paper "Typing Haskell in Haskell" (THIH), it looks like the predicates (Num a, Eq a) should cause an ambiguity in the definition of g: * a is present in the definition of f, but not the definition of g * so the type (Eq a, Num a) => Char -> Char -> Char is ambiguous. * more generally, it seems like THIH treats any predicates with a type variable that is part of some, but not all, types in the declaration group to be ambiguous. Does this sound right? 4. Then, again following THIH, this ambiguous predicate should be defaulted to Int. I THINK this should lead to f :: Char -> Int -> Char g :: Char -> Char -> Char 5. However, I'm still not sure I'm understanding this right, because a few things still don't make sense: * First, THIH seems to eliminate the defaulted predicates without substituting a -> Int. But the type for f DOES mention `a`, so how can we avoid substituting? * Second, GHC accepts the code with no warnings or errors. There is some kind of defaulting going on, because GHC rejects the code if I add "default ()". Is there some way for GHC to default only g, but not f? I wonder if this involves a difference between Haskell '98 and Haskell 2010? I also wonder how much I should rely on THIH? Maybe the language has moved on since then? -BenRI

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Recursive constraints with type families
by Dmitriy Matrosov 26 Jan '22

26 Jan '22

Hi. I've stumbled upon a simple problem with recursive type family: > {-# LANGUAGE RankNTypes #-} > {-# LANGUAGE KindSignatures #-} > {-# LANGUAGE TypeApplications #-} > {-# LANGUAGE TypeOperators #-} > {-# LANGUAGE PolyKinds #-} > {-# LANGUAGE TypeFamilies #-} > {-# LANGUAGE StandaloneKindSignatures #-} > {-# LANGUAGE ScopedTypeVariables #-} > {-# LANGUAGE UndecidableInstances #-} > > import GHC.TypeLits > import Data.Proxy > import Data.Kind > > type C :: Nat -> Constraint > type family C x where > C 0 = KnownNat 0 > --C x = (KnownNat x, C (x - 1)) > C x = (KnownNat x, C 0) > --C x = KnownNat x > > --type C2 x = (KnownNat x, C2 1) > > showNat :: forall (n :: Nat). C n => Proxy n -> String > showNat _ = show $ natVal (Proxy @n) and the error is Prelude> :r [1 of 1] Compiling Main ( constraint-type-family.lhs, interpreted ) constraint-type-family.lhs:31:22: error: • Could not deduce (KnownNat n) arising from a use of ‘natVal’ from the context: C n bound by the type signature for: showNat :: forall (n :: Nat). C n => Proxy n -> String at constraint-type-family.lhs:30:3-56 Possible fix: add (KnownNat n) to the context of the type signature for: showNat :: forall (n :: Nat). C n => Proxy n -> String • In the second argument of ‘($)’, namely ‘natVal (Proxy @n)’ In the expression: show $ natVal (Proxy @n) In an equation for ‘showNat’: showNat _ = show $ natVal (Proxy @n) | 31 | > showNat _ = show $ natVal (Proxy @n) | ^^^^^^^^^^^^^^^^^ If i write just C x = KnownNat x everything works fine. I guess, the reason is UndecidableInstances, but why and then, how can i build constraints recursively and make it work? Thanks. PS. Initially, this 'showNat' was something like countDown :: forall (n :: Nat). C n => Proxy n -> String countDown _ = let x = natVal (Proxy @n) in if x > 0 then show x ++ countDown (Proxy @(n - 1)) else "end" but it does not work.

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Missing feature of Coercible, or necessary caution?
by Tom Ellis 25 Jan '22

25 Jan '22

Consider the following program. {-# LANGUAGE TypeApplications #-} import Data.IntMap (IntMap, mapKeysMonotonic, Key) import Data.Coerce (coerce) newtype MyMap = MyMap (IntMap Bool) doesn'tWork :: (Key -> Key) -> MyMap -> MyMap doesn'tWork = coerce mapKeysMonotonic works :: (Key -> Key) -> MyMap -> MyMap works = coerce (mapKeysMonotonic @Bool) mapKeysmonotonic has type (Key -> Key) -> IntMap a -> IntMap a and we attempt to coerce it to type (Key -> Key) -> MyMap -> MyMap since MyMap is a newtype around IntMap Bool this ends up generating the constraint Coercible a Bool and there is no way to specify that constraint given that a doesn't otherwise appear in the top-level type. Hence doesn'tWork will not type check. If I force the type of a to be Bool using a TypeApplication then it does type check (works). But is this a missing feature of GHC's Coercible system? Since a is not otherwise constrained is it not valid for GHC to choose it to be Bool ? Coercible instances contain now observable content so no observable behaviour could depend on the particular choice of Coercible a Bool instance, and choosing a ~ Bool is the natural one. Is there some violation of type safety or otherwise broken behaviour that could arise from choosing arbitrary Coercible instances on type variables that are not otherwise constrained? Tom

2 2

Guards on variable bindings
by Tom Ellis 24 Jan '22

24 Jan '22

According to GHC there are multiple declarations of bar, but not of foo. I don't understand. Why is it not valid to have multiple clauses for a variable binding? Tom bar | False = () bar = () foo _ | False = () foo _ = ()

2 4

why OverloadedTuples extension is missing?
by Daneel Yaitskov 17 Jan '22

17 Jan '22

Cafe, There is a group of GHC extensions and complementary classes to make writing Haskell code a bit sweeter such as: - {} - Num (fromIntegral) - OverloadedStrings - IsString - OverloadedLists - IsList So I have an inductive question - why there is no OverloadedTuples? I haven't found a discussion thread about this topic. I could imagine following tuple syntax interpretation: {-# LANGUAGE OverloadedTuples #-} data Foo = FooA Int String | FooB String Foo deriving (Show, Eq, IsTuple) mkFoo :: Foo mkFoo = (1, "hello") mkFoo2 :: Foo mkFoo = ("abc", (1, "hello")) Sometimes expected type name is known without data constructor. So such expression is more concise. -- Best regards, Daniil Iaitskov

8 7

Newbie question
by Terry Phelps 16 Jan '22

16 Jan '22

I'm trying yet again to "get" Haskell. I'm reading Graham Hutton's book "Programming in Haskell", and am working on one of the exercises. Sounds easy enough: Make a function 'last' that returns the last element of a non-empty list. After struggling a while, I looked at the answer: last = head . reverse. I wish I had thought of that. But I kept trying to get my recursive version done, but I can't seem to make ghci happy. (Version 8.10.5, if you care). I wrote: last [] = [] (Yes, I know that's not a non-empty list, but I don't want ghci whining about non-exhaustive patterns). Then I added: last [x] = x And I checked the type: :t last last:: [a] -> [a] Yes, that looks right. There seems to be only one other case: 2 or more elements. So I wrote: last (x:y:xs) = last (y:xs) I ran it: Prelude> last [1,2] *** Exception: <interactive>:2:1-27: Non-exhaustive patterns in function last What the heck is the problem? I've covered every possible list, haven't I? Stranger yet, I check the type again: Prelude> :t last last :: [a] -> t The type has changed. And I don't understand what it means. What's the 't'? I'm sure this is a simple beginner error, but I'm really confused. I don't see how it isn't exhaustive, and I don't see why the 3rd clause (or whatever it's called) caused the type to change. Someone help, please.

5 6

TFPIE 2022: moving to online and extension to Feb 7th
by Elena Machkasova 14 Jan '22

14 Jan '22

Due to rescheduling of the Lambda Days because of COVID, TFPIE, together with TFP, will be held virtually on March 16th 2022, together with TFP which will be held on March 17-18. There is an optional opportunity to present at the Lambda Days July 28-29 2022 in addition to the virtual presentation in March. Updated TFPIE 2022 Call for papers: https://wiki.tfpie.science.ru.nl/TFPIE2022 The submission deadline is extended to February 7th 2022. TFPIE 2022 welcomes submissions describing techniques used in the classroom, tools used in and/or developed for the classroom and any creative use of functional programming (FP) to aid education in or outside Computer Science. Topics of interest include, but are not limited to: FP and beginning CS students FP and Computational Thinking FP and Artificial Intelligence FP in Robotics FP and Music Advanced FP for undergraduates FP in graduate education Engaging students in research using FP FP in Programming Languages FP in the high school curriculum FP as a stepping stone to other CS topics FP and Philosophy The pedagogy of teaching FP FP and e-learning: MOOCs, automated assessment etc. Best Lectures - more details below In addition to papers, we are requesting best lecture presentations. What's your best lecture topic in an FP related course? Do you have a fun way to present FP concepts to novices or perhaps an especially interesting presentation of a difficult topic? In either case, please consider sharing it. Best lecture topics will be selected for presentation based on a short abstract describing the lecture and its interest to TFPIE attendees. The length of the presentation should be comparable to that of a paper. In addition, the speaker can provide commentary on effectiveness or student feedback. Submissions Potential presenters are invited to submit an extended abstract (4-6 pages) or a draft paper (up to 20 pages) in EPTCS style. The authors of accepted presentations will have their preprints and their slides made available on the workshop's website. Papers and abstracts can be submitted via easychair at the following link: https://easychair.org/conferences/?conf=tfpie2022 After the workshop, presenters are invited to submit (a revised version of) their article for the formal review. The PC will select the best articles for publication in the Electronic Proceedings in Theoretical Computer Science (EPTCS). Articles rejected for presentation and extended abstracts will not be formally reviewed by the PC. Important Dates (updated) Submission deadline: *February 7th* 2022, Anywhere on Earth. Notification: *February 11th* 2022 (Note: earlier submissions will receive earlier response) TFPIE Registration Deadline: TBA Workshop: *March 16* 2022 Submission for formal review: *April 29th* 2022, Anywhere on Earth. Notification of full article: June 1st 2022 Camera ready: July 1st 2022 Program Committee Peter Achten, Radboud University, Netherlands Stephen Chang, University of Massachusetts Boston, USA John Hughes, Chalmers University of Technology, Sweden Elena Machkasova (Chair) - University of Minnesota Morris, USA Kristina Sojakova - INRIA, Paris, France Melinda Tóth, Eötvös Loránd University, Budapest, Hungary Keynote speaker: Our keynote talk is "The perfect Functional Programming course" by Peter Achten. Registration information: TFPIE will take place virtually on March 16 2022, together with TFP which will be held on March 17-18. Registration information will be announced shortly. There is no registration fee. Registration and online attendance are mandatory for at least one author of every paper that is presented at the workshop. Only papers that have been presented at TFPIE may be submitted to the post-reviewing process. -- Dr. Elena Machkasova Associate Professor of Computer Science Division of Science and Mathematics University of Minnesota, Morris Office: Sci 2325 (320) 589-6308 http://cda.morris.umn.edu/~elenam/ Pronouns: she/her/hers or any other

1 0

Postdoc positions on Formal Verification for Zero-Trust IoT Systems at Kyoto University and National Institute of Informatics (NII), Japan
by Taro Sekiyama 14 Jan '22

14 Jan '22

[Please distribute, apologies for multiple postings.] Dear All, We are seeking a few postdoc researchers, who works for a project “Zero-Trust IoT Systems by Collaboration of Formal Verification and System Software” by Japan Science and Technology Agency. We'd be grateful if you could spread the word to interested candidates. * Project Description The project aims at the construction of formally verified secure IoT systems that follow the concept of “zero trust architecture”, dubbed ZT-IoT systems. It consists of four research teams and two teams, led by Atsushi Igarashi, Kyoto University, Japan and Taro Sekiyama, National Institute of Informatics, Japan (NII) are investigating applications of formal verification or programming language techniques to the construction of secure IoT systems. The main research topic of Igarashi’s team is centered around the design and theory of security policy engines for ZT-IoT systems, inclucing the design of a language to describe security policies and policy enforcement algorithms and the techniques for verifying policy enforcement algorithms against given security policies. Other team members are Kohei Suenaga and Masaki Waga at Kyoto University. The main research topic of Sekiyama’s team is centered around techniques for monitoring and intervention for ZT-IoT systems. Other team members include Ichiro Hasuo and Shin-ya Katsumata at NII. Although the two teams are based in different places, we collaborate closely with each other. The appointment can start as early as April 2022 (the starting date is negotiable). The contract will initially run until the end of March 2023, with the possibility of annual renewal until the end of the project, which is March 2027 at maximum. Salary will be about 360,000–550,000 JPY/month. Applicants should have a Ph.D in computer science or related fields, and have a strong background in formal verification and/or programming language theory. Due to the project’s nature, they are required to have strong interests in applying theory to practice; they should also be (self-)motivated, dedicated, and able to work both independently and collaboratively. Strong communication skills in oral and written English are required. * Workplace Members of Igarashi’s team will work at Kyoto University, Kyoto, Japan and members of Sekiyama’s team will work at NII, Tokyo, Japan. (Living costs in Japan are not very high nowadays. An estimate is found here https://www.internations.org/go/moving-to-japan/living/the-cost-of-living-i… and we find rent can be cheaper than the cited amount.) * Applications and inquiries Inquiries can be sent to application-zt-iot [at] fos.kuis.kyoto-u.ac.jp, with the subject CREST Job Inquiry. Feel free to ask us any questions on relevance, topics, compensation, etc. We will reply when we see enough relevance. Applications should be made electronically via the following JREC-IN Portal web sites. NII: https://jrecin.jst.go.jp/seek/SeekJorDetail?fn=3&ln=1&id=D122010021&ln_jor=1 Kyoto: https://jrecin.jst.go.jp/seek/SeekJorDetail?fn=3&ln=1&id=D121122219&ln_jor=1 Please upload a pdf including - your brief CV, - short description of research interests (can be very informal and short), - the list of papers (a dblp or Google scholar link will do, for example), - a couple of representative papers (in pdf), and - (preferably) the contact of two references. We will contact you for further material and interview, provided that we find sufficient relevance in your application. Starting dates are negotiable. The positions will remain open until filled. Many thanks, Taro.

1 0

Call for Participation: BOB 2022 (March 11, Berlin or online)
by Stefan Wehr 13 Jan '22

13 Jan '22

================================================================================ BOB 2022 Conference “What happens if we simply use what’s best?” March 11, 2022, Berlin or online 0100+UTC https://bobkonf.de/2022/ Program: https://bobkonf.de/2022/program.html Berlin or online? Fill out our survey: https://bobkonf.de/2022/onsite.html ================================================================================ BOB conference is a place for developers, architects, and decision-makers to explore technologies beyond the mainstream in software development and to find the best tools available to software developers today. Our goal is for all participants of BOB to return home with new insights that enable them to improve their own software development experience. The program features 14 talks and 8 tutorials on current topics: https://bobkonf.de/2022/program.html The subject range includes functional programming, effects, distributed programming, formal methods, generative art, event-driven systems, the human brain, Haskell, Python, Scala, Lua, Clojure, Erlang, Nix, and others. Derek Dreyer will give the keynote talk. NOTE: We will decide on January 17 whether BOB 2022 will take place on-site in Berlin or online. Either way, we are working towards fostering a lively exchange of exciting ideas and enabling meaningful social interactions. We're collecting feedback on the issue here: https://bobkonf.de/2022/onsite.html If you're interested in BOB, please take a minute to fill the survey linked above! Registration will also open on January 17, once the decision for on-site or online has been made.

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[TFP'22] second call for papers: Trends in Functional Programming 2022 moved to March 17-18 online (together with TFPiE)
by Peter Achten 11 Jan '22

11 Jan '22

============== TFP 2022 =================== == MOVING TO ONLINE SYMPOSIUM, NEW DATES == =========================================== 23rd Symposium on Trends in Functional Programming 17-18 March, 2022 Online event https://trendsfp.github.io/index.html Due the pandemic, we have had to make TFP virtual this year. As a result, we've decided to push back the deadlines and conference date by a few weeks. In particular, the pre-symposium deadline for submitting the first version of your paper is now just after the ICFP deadline. == Important Dates == Submission deadline for draft papers Monday 7th March, 2022 Notification for draft submissions Friday 11th March, 2022 Symposium dates Thursday 17th - Friday 18th March, 2022 Submission deadline for post-symposium reviewing Wednesday 6th April, 2022 Notification for post-symposium submissions Friday 27th May, 2022 The Symposium on Trends in Functional Programming (TFP) is an international forum for researchers with interests in all aspects of functional programming, taking a broad view of current and future trends in the area. It aspires to be a lively environment for presenting the latest research results, and other contributions. == Scope == The symposium recognizes that new trends may arise through various routes. As part of the Symposium's focus on trends we therefore identify the following five article categories. High-quality articles are solicited in any of these categories: * Research Articles: Leading-edge, previously unpublished research work * Position Articles: On what new trends should or should not be * Project Articles: Descriptions of recently started new projects * Evaluation Articles: What lessons can be drawn from a finished project * Overview Articles: Summarizing work with respect to a trendy subject Articles must be original and not simultaneously submitted for publication to any other forum. They may consider any aspect of functional programming: theoretical, implementation-oriented, or experience-oriented. Applications of functional programming techniques to other languages are also within the scope of the symposium. Topics suitable for the symposium include, but are not limited to: * Functional programming and multicore/manycore computing * Functional programming in the cloud * High performance functional computing * Extra-functional (behavioural) properties of functional programs * Dependently typed functional programming * Validation and verification of functional programs * Debugging and profiling for functional languages * Functional programming in different application areas: security, mobility, telecommunications applications, embedded systems, global computing, grids, etc. * Interoperability with imperative programming languages * Novel memory management techniques * Program analysis and transformation techniques * Empirical performance studies * Abstract/virtual machines and compilers for functional languages * (Embedded) domain specific languages * New implementation strategies * Any new emerging trend in the functional programming area If you are in doubt on whether your article is within the scope of TFP, please contact the TFP 2022 program chairs, Wouter Swierstra and Nicolas Wu. == Best Paper Awards == To reward excellent contributions, TFP awards a prize for the best paper accepted for the formal proceedings. TFP traditionally pays special attention to research students, acknowledging that students are almost by definition part of new subject trends. A student paper is one for which the authors state that the paper is mainly the work of students, the students are listed as first authors, and a student would present the paper. A prize for the best student paper is awarded each year. In both cases, it is the PC of TFP that awards the prize. In case the best paper happens to be a student paper, that paper will then receive both prizes. == Instructions to Author == Papers must be submitted at: https://easychair.org/conferences/?conf=tfp22 Authors of papers have the choice of having their contributions formally reviewed either before or after the Symposium. == Post-symposium formal review process == Draft papers will receive minimal reviews and notification of acceptance for presentation at the symposium. Authors of draft papers will be invited to submit revised papers based on the feedback received at the symposium. A post-symposium refereeing process will then select a subset of these articles for formal publication. == Paper categories == Draft papers and papers submitted for formal review are submitted as extended abstracts (4 to 10 pages in length) or full papers (20 pages). The submission must clearly indicate which category it belongs to: research, position, project, evaluation, or overview paper. It should also indicate which authors are research students, and whether the main author(s) are students. A draft paper for which all authors are students will receive additional feedback by one of the PC members shortly after the symposium has taken place. == Format == Papers must be written in English, and written using the LNCS style. For more information about formatting please consult the Springer LNCS web site. == Program Committee == Guillaume Allais University of St Andrews José Manuel Calderón Trilla Galois, Inc. Stephen Chang University of Massachusetts Boston Matthew Flatt University of Utah Jeremy Gibbons University of Oxford Zhenjiang Hu Peking University Mauro Jaskelioff CIFASIS / Universidad Nacional de Rosario Moa Johansson Chalmers University of Technology Shin-ya Katsumata National Institute of Informatics Oleg Kiselyov Tohoku University Bas Lijnse Netherlands Defence Academy / Radboud University Nijmegen Kazutaka Matsuda Tohoku University Nico Naus Virginia Tech Christine Rizkallah University of New South Wales Alejandro Serrano 47 Degrees Amir Shaikhha Ecole Polytechnique Fédérale de Lausanne Aaron Stump University of Iowa Wouter Swierstra (Co-chair) Utrecht University Baltasar Trancón Y Widemann Semantics GmbH Nicolas Wu (Co-chair) Imperial College London Ningning Xie University of Hong Kong

1 0

[ANN] plutus-simple-model - unit test linrary for plutus with resource estimation
by Anton Kholomiov 11 Jan '22

11 Jan '22

Hi! I’d like to announce the unit test library plutus-simple-model <https://github.com/mlabs-haskell/plutus-simple-model> for plutus that is a joy to use [1]. It’s simple and easy to grasp and it can estimate resource usage for TX (size and execution units). Main idea is to implement a simple blockchain model that updates UTXOs inside a pure State monad if TX is valid. To check TX cardano node functions are used so the check is the same as if node would check it and it produces useful stats for resource usage. Benefits comparing to EmulatorTrace to me: - I find resource usage stats are useful to know in production and this is missing in Emulator tests - EmulatorTrace approach makes it hard to query run-time information and with given lib it’s super easy - Having to define separate API and use lookups/constraints seems clumsy to me. It often leads to writing lots of boilerplate code. - it’s much faster to run I’ve tested it successfully in one project and using it for the second one. It has great docs and tutorials. Enjoy! I hope it will improve your testing experience with plutus. [1] plutus-simple-model <https://github.com/mlabs-haskell/plutus-simple-model> https://github.com/mlabs-haskell/plutus-simple-model

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[CFP closing soon!] Functional Conf 2022 Call for Proposals close 15 Jan
by John Sinclair 11 Jan '22

11 Jan '22

Just 4 days remain to submit proposals for speaking at Functional Conf <https://signal2domain.online/click?redirect=https%3A%2F%2Fllink.to%2F%3Fu%3… Conf> 2022. This is an online opportunity for you to contribute to Asia’s most vibrant functional programming conference. All selected speakers get a free ticket to the conference. Share your knowledge of Haskell and connect with programmers actively contributing to the development of FP languages, developers using it in their day-to-day programming and those just getting started on their FP journey. There’s something for everyone! At our last conference we featured keynotes from international guests Edward Kmett <https://signal2domain.online/click?redirect=https%3A%2F%2Fllink.to%2F%3Fu%3… Kmett> (Chairman, Haskell Core Libraries Committee), Michael Snoyman <https://signal2domain.online/click?redirect=https%3A%2F%2Fllink.to%2F%3Fu%3… Snoyman> (VP Engineering at FP Complete) and Tony Morris <https://signal2domain.online/click?redirect=https%3A%2F%2Fllink.to%2F%3Fu%3… Morris> (Sr. Software Engineer at Queensland FP Lab). Will you join us as a speaker this year? This year we are focusing on the themes of: - Applying FP - Applying FP sessions are targeted at Developers, who understand the basics of FP, maybe even practice some FP at work. Helping them understand how they can apply even more FP concepts more at work. - FP Bootcamp - FP Bootcamp is targeted at Developers, who want to kick start their FP journey. - Mastering FP - Mastering FP sessions are targeted at Developers, who already apply a decent amount of FP concepts at work. Developers, who want to go deeper and maybe even become a contributor to a FP language or library. Session Formats - Talks/Case-Studies (20 or 45 minutes) - Demos (20 or 45 minutes) - Experience Reports (20 minutes) - Hands-on workshop/tutorials (45 or 90 minutes) Proposal submission deadline: 15 January Learn more and submit your proposal: https://confng.in/qXN4WvpA <https://signal2domain.online/click?redirect=https%3A%2F%2Fllink.to%2F%3Fu%3…>

1 0

strange link error
by PICCA Frederic-Emmanuel 10 Jan '22

10 Jan '22

Hello, I try to build a project which use C libraries. during the developpement I want to link directly with the work in progress libraries. So I added this in cabal. executable binoculars-ng [...] if flag(useHklDev) pkgconfig-depends: gobject-2.0 ghc-options: -pgml ghc-options: gcc ghc-options: "-optl-Wl,--allow-multiple-definition" ghc-options: "-optl-Wl,--whole-archive,../../hkl/.libs/libhkl.a,--no-whole-archive" ghc-options: "-optl-Wl,--whole-archive,../../binoculars/libhkl-binoculars.a,--no-whole-archive" at the end I have a working executable. Building executable 'binoculars-ng' for hkl-0.1.0.0.. [1 of 1] Compiling Main ( app/Binoculars.hs, /home/experiences/instrumentation/picca/src/repo.or.cz/hkl/contrib/haskell/dist-newstyle/build/x86_64-linux/ghc-8.8.4/hkl-0.1.0.0/x/binoculars-ng/build/binoculars-ng/binoculars-ng-tmp/Main.o ) Linking /home/experiences/instrumentation/picca/src/repo.or.cz/hkl/contrib/haskell/dist-newstyle/build/x86_64-linux/ghc-8.8.4/hkl-0.1.0.0/x/binoculars-ng/build/binoculars-ng/binoculars-ng ... But now I would like to create an unit test so I added this in cabal test-suite hkl-test [...] if flag(useHklDev) pkgconfig-depends: gobject-2.0 ghc-options: -pgml ghc-options: gcc ghc-options: "-optl-Wl,--allow-multiple-definition" ghc-options: "-optl-Wl,--whole-archive,../../hkl/.libs/libhkl.a,--no-whole-archive" ghc-options: "-optl-Wl,--whole-archive,../../binoculars/libhkl-binoculars.a,--no-whole-archive" but this time during the compilation I end up with this error message [1 of 3] Compiling Paths_hkl ( /home/experiences/instrumentation/picca/src/repo.or.cz/hkl/contrib/haskell/dist-newstyle/build/x86_64-linux/ghc-8.8.4/hkl-0.1.0.0/t/hkl-test/build/hkl-test/autogen/Paths_hkl.hs, /home/experiences/instrumentation/picca/src/repo.or.cz/hkl/contrib/haskell/dist-newstyle/build/x86_64-linux/ghc-8.8.4/hkl-0.1.0.0/t/hkl-test/build/hkl-test/hkl-test-tmp/Paths_hkl.o ) [2 of 3] Compiling BinocularsSpec ( test/BinocularsSpec.hs, /home/experiences/instrumentation/picca/src/repo.or.cz/hkl/contrib/haskell/dist-newstyle/build/x86_64-linux/ghc-8.8.4/hkl-0.1.0.0/t/hkl-test/build/hkl-test/hkl-test-tmp/BinocularsSpec.o ) <command line>: /home/experiences/instrumentation/picca/src/repo.or.cz/hkl/contrib/haskell/dist-newstyle/build/x86_64-linux/ghc-8.8.4/hkl-0.1.0.0/build/libHShkl-0.1.0.0-inplace-ghc8.8.4.so: undefined symbol: hkl_binoculars_cube_free both the executable and the test use this hkl_binoculars_cube_free function. So are you aware of a difference between test suit and executable during the build. more precisely are both executables compiled differently ? thanks for you help Frederic

3 7

Do something about Cabal?
by Ignat Insarov 03 Jan '22

03 Jan '22

# Do something about Cabal? Hello. Cabal is the second most used tool in Haskell after GHC. It has many problems. It may be noticed that there is one and a half developers working on it. This is clearly not enough to address these problems. I propose that this is a good place to invest in. ### Problems I have in mind: * Poor communication, lack of open source development process. The whole Cabal–Stack schism appears to be an outcome of poor communication. One of the leading developers of Cabal is even banned from participation somewhere in Stack circles.[1] Personally, I reported several issues to Cabal and every single time it resulted in sadness. Observe a vicious circle: core developers are overworked ⇒ they are being unfriendly ⇒ there are fewer contributors ⇒ core developers are overworked. I have no hard evidence but it appears that presently, more people that strive to improve the Haskell build experience are outside the Cabal cabal than are inside. * User experience is an afterthought. Cabal's user experience is horrifying. A collection of complaints is being compiled elsewhere.[2] There are also bugs being opened to Cabal because of this, requiring triage and therefore wasting the precious time of the few overworked developers. Stack is much more friendly — this shows by example that the user experience problem is not inherent and may be solved. It is ordinary to receive output like this: ``` % cabal run example-executable Warning: The package list for 'hackage.haskell.org' is 84 days old. Run 'cabal update' to get the latest list of available packages. Resolving dependencies... cabal: Could not resolve dependencies: [__0] trying: example-0.1.0.6 (user goal) [__1] next goal: opaleye (dependency of example) [__1] rejecting: opaleye-0.7.1.0, opaleye-0.7.0.0 (constraint from project config TODO requires ==0.6.7006.1) [__1] rejecting: opaleye-0.6.7006.1 (conflict: example => opaleye^>=0.7) [__1] skipping: opaleye-0.6.7006.0, opaleye-0.6.7005.0, opaleye-0.6.7004.2, opaleye-0.6.7004.1, opaleye-0.6.7004.0, opaleye-0.6.7003.1, opaleye-0.6.7003.0, opaleye-0.6.1.0, opaleye-0.6.0.0, opaleye-0.5.4.0, opaleye-0.5.3.1, opaleye-0.5.3.0, opaleye-0.5.2.2, opaleye-0.5.2.0, opaleye-0.5.1.1, opaleye-0.5.1.0, opaleye-0.5.0.0, opaleye-0.4.2.0, opaleye-0.4.1.0, opaleye-0.4.0.0, opaleye-0.3.1.2, opaleye-0.3.1, opaleye-0.3, opaleye-0.2, opaleye-0.6.7002.0, opaleye-0.6.7001.0, opaleye-0.6.7000.0, opaleye-0.5.2.1, opaleye-0.3.1.1 (has the same characteristics that caused the previous version to fail: excluded by constraint '^>=0.7' from example) [__1] fail (backjumping, conflict set: example, opaleye) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: opaleye, example ``` There are so many things that are wrong here. Even a sneaky _«to do»_ remark. If you wonder, in this case the solution is to remove and re-generate `cabal.project.freeze`. Even the name of the program — it is actually _«cabal-install»_ — is incomprehensible, it should be re-branded to Cabal, which is how everyone calls it anyway. * Features are not being introduced. There is no reason for two build tools to exist. The killer feature of Stack — snapshots — should be supported by Cabal. Possibly Cabal itself should be refactored and split so that there are separate tools for packaging, version resolution and human interaction — I do not know. But certainly the way things are presently is a waste of developer effort and a source of confusion for everyone. ### My proposition, in particular. * Ask all the people that show compassion to the cause of a great Haskell build tool to unite and work together on a better Cabal. This includes the developers of Stack and everyone that expressed unhappiness with the current state of Cabal. These people should be seen as a blessing, not as an obstacle. * Put in place a clear process for contributing and decision making, so that it does not come down to the privileged opinion of one of the core developers. * Make a model of user experience that Cabal should conform to, and make conformance a priority. Surely there are among us people that know a thing or two about user experience — call for them to step forward. Every issue that stems from misunderstanding, re-assign to the model instead of closing. * Merge the support of Stackage snapshots into Cabal. Ask the core developers of Stack to join the effort. Transition from Stack to Cabal should be one well discoverable command that just works. I realize that this letter is largely an opinion piece. You can also see it as an _«ideal piece»_. Without an ideal, without a vision, we are stuck with the present. I do not insist that my vision is the best. But the present reality is not the best vision either. I propose, foremost, that we work and fight for a better future. [1]: https://github.com/commercialhaskell/stackage/issues/4472 [2]: https://github.com/tomjaguarpaw/tilapia/issues?q=is%3Aissue+is%3Aopen+cabal

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Managing state between client/server (frontend/backend)
by Clinton Mead 02 Jan '22

02 Jan '22

A happy new year to all the Haskell community. My current role involves an app with a Scala backend and a React/Redux Javascript frontend. What should be quite simple tasks are made difficult/impossible, firstly by the fact if you even touch a Javascript codebase in any significant way you break the code in weird and wonderful ways, which may only be apparent as random runtime errors days, weeks or months in the future, but another issue is that tracking some bug back from the browser to the backend and the database is a nightmare because it's far from obvious what's going on across the language boundary between Scala and Javascript, particularly as everything is being flattened to JSON across that boundary. Anyway, I was thinking of a better way of doing this, and I thought it would be nice if much of the code was shared between the browser frontend and backend server though a common datatype, with the frontend just compiled with GHCJS. Some of the state to the client could be readonly, and some writable. The actual details of pushing the data back and forth would be abstracted away (as much as possible). When the client does writes, it wouldn't need to wait for the server to process these writes, it could just save these on the client side state, and send them off to the server to record, but otherwise continue on. There's quite a few nuances here I've started to think about (and there's likely more I haven't thought about) and given that I don't think this idea is particularly novel, are there any libraries out there that already do roughly what I'm talking about here? If someone has already thought this through I don't want to reinvent the wheel.

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text-2.0 with UTF8 is finally released!
by Andrew Lelechenko 26 Dec '21

26 Dec '21

I’m happy to announce that text-2.0 with UTF-8 underlying representation has been finally released: https://hackage.haskell.org/package/text-2.0. The release is identical to rc2, circulated earlier. Changelog: https://hackage.haskell.org/package/text-2.0/changelog Please give it a try. Here is a cabal.project template: https://gist.github.com/Bodigrim/9834568f075be36a1c65e7aaba6a15db This work would not be complete without a blazingly-fast UTF-8 validator, submitted by Koz Ross into bytestring-0.11.2.0, whose contributions were sourced via HF as an in-kind donation from MLabs. I would like to thank Emily Pillmore for encouraging me to take on this project, helping with the proposal and permissions. I’m grateful to my fellow text maintainers, who’ve been carefully reviewing my work in course of the last six months, as well as helpful and responsive maintainers of downstream packages and GHC developers. Thanks all, it was a pleasant journey! Best regards, Andrew

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[Haskell] [ANNOUNCE] GHC 9.0.2 released
by Zubin Duggal 25 Dec '21

25 Dec '21

The GHC developers are very happy to at long last announce the availability of GHC 9.0.2. Binary distributions, source distributions, and documentation are available at the [usual place](https://downloads.haskell.org/ghc/9.0.2/). Download Page: https://www.haskell.org/ghc/download_ghc_9_0_2.html Blog Post: https://www.haskell.org/ghc/blog/20211225-ghc-9.0.2-released.html GHC 9.0.2 adds first class AArch64/Darwin support using the LLVM backend, as well as fixing a number of critical correctness bugs with the 9.0.1 release, along with numerous improvements to compiler performance and memory usage: * First-class support for Apple M1 hardware using GHC's LLVM ARM backend. * Fix a number of incorrect rewrite rules for `fromInteger` (#19345, #20066). * Fix a number of runtime system and GC bugs which typically manifested in crashes (#19417, #19297, #19645, #19667, #18033, #20132, #19715, #20399, #20414, #20649, #19147, #20051, #20093) * Fixes for various compiler performance and memory usage issues (#20134, #13586, #20509, #19668, #19996, #19471) * Improvements and bug fixes for the code generator and optimiser (#18638, #19581, #19700, #19996, #19181, #19822) * Fixes for typechecker bugs (#19410 , #19191, #19522, #19400, #19849) * Bug fixes for the frontend and parser (#19397, #19838, #19518, #19777, #20242, #19786) * Emit warnings if Unicode Bidirectional Formatting characters are found in the source, possibly misleading code reviewers (#20263). * Many packaging related fixes, including versioned `ghc-pkg` executables (#20087), and actually distributing GHC versions linked against the `native` big integer backend (#18967, #19953) on both Windows and Alpine Linux. Some previous releases were still linked against the `GMP` library due to a misconfiguration of the builders. * A significant refactoring of `process` fixing numerous bugs mostly on Apple platforms (#19994, [process refactoring](https://github.com/haskell/process/pull/208)) * Bug fixes for the linker on Darwin platforms (#20004, #19968, #19950). A complete list of bug fixes and improvements can be found in the [release notes](https://downloads.haskell.org/ghc/9.0.2/docs/html/users_guide/9.0.2-…. Finally, thank you to Microsoft Research, GitHub, IOHK, 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. Moreover, this release would not have been possible without the hundreds of open-source contributors whose work comprise this release. As always, do open a [ticket][] if you see anything amiss. Happy Holidays and Happy Hacking! - Zubin

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CFP (Deadline Extended): The 5th International Conference on Emerging Data and Industry 4.0 (EDI40) Porto, Portugal March 22-25, 2022
by Shashank Swarup 24 Dec '21

24 Dec '21

*************************************************************************** The 5th International Conference on Emerging Data and Industry 4.0 (EDI40) Porto, Portugal March 22-25, 2022 *************************************************************************** Conference Website: http://cs-conferences.acadiau.ca/EDI40-22/ Workshops: http://cs-conferences.acadiau.ca/EDI40-22/#workshop Important Dates - Workshops Proposals Due: October 1, 2021 * - Paper Submission Due: December 30, 2021 (Revised & Firm)* - Acceptance Notification: January 15, 2022 - Camera-Ready Submission: February 10, 2022 EDI40 2022 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 and on Elsevier content platform ScienceDirect (www.sciencedirect.com) and will be freely available worldwide. All papers in Procedia will be indexed by Scopus ( www.scopus.com) and by Thomson Reuters' Conference Proceeding Citation Index (http://thomsonreuters.com/conference-proceedings-citation-index/) All papers in Procedia will also be indexed by Scopus (www.scopus.com) and Engineering Village (Ei) (www.engineeringvillage.com) This includes EI Compendex (www.ei.org/compendex) Moreover, all accepted papers will be indexed in DBLP (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) - International Journal Personal and Ubiquitous Computing (IF:3.006), Springer (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… ) - International Journal of Computing and Informatics (IF: 0.524), by Computing and Informatics (http://www.cai.sk/ojs/index.php/cai/index) EDI40 2022 will be held in Porto, Portugal. Porto is the second-largest city in Portugal after Lisbon and one of the major urban areas of the Iberian Peninsula. Porto is also called the Invicta because during the 19th century Portuguese civil war, the city withstood a siege of over a year.The urban area of Porto, which extends beyond the administrative limits of the city, has a population of 2.1 million in an area of 389 km2 (150 sq mi), making it the second-largest urban area in Portugal. It is recognized as a gamma- level global city by the Globalization and World Cities (GaWC) Study Group, the only Portuguese city besides Lisbon to be recognized as a global city. EDI40 will be held in conjunction with the 13th International Conference on Ambient Systems, Networks and Technologies (ANT 2022). Conference Tracks - Benefits of Industry 4.0 - Big Data and Analytics - Cloud Computing - Cognitive Computing - Computational Intelligence - Cyber-Physical Systems (CPS) - Fog Computing and Edge Computing - Internet of Everything (IoE) - Standards for IoT Application Integration - The New Business Models in Industry 4.0 - General Track: Digitalization Startegies Committees General Chair Danny Hughes, CTO VeraSense NV, Belgium Program Chairs Jamal Bentahar, Concordia University, Canada Haroon Malik, Marshall University, USA Local Chair Nuno Varandas, F6S (Where Founders Grow Together), Portugal Workshops Chair Stephane Galland, UTBM, France Program Advisory Committee Reda Alhajj, University of Calgary, Canada Ladislav Hluchy, Institute of Informatics, Slovak Academy of Sciences, Slovakia Vincenzo Loia, University of Salerno, Italy Peter Sloot, Universiteit van Amsterdam, Netherlands Peter Thomas, Manifesto Research, Australia Mohamed Younis, University of Maryland Baltimore County, USA International Journals Chair Michael Sheng, Macquarie University, Australia Publicity Chairs Wim Ectors, Hasselt University, Belgium Faouzi Kammoun, Ecole SupÃƒÂ©rieure PrivÃƒÂ©e d'IngÃƒÂ©nierie et de Technologies, Tunis Aneta Poniszewska-MaraÃ…â€žda, Lodz University of Technology, Poland Shashank Swarup, Acadia University, Canada Technical Program Committee http://cs-conferences.acadiau.ca/EDI40-22/#programCommittees International Liaison Chairs Soumaya Cherkaoui, Sherbrooke University, Canada Nik Bessis, Edge Hill University, UK David Taniar, Monash University, Australia Steering Committee Chair and Founder Elhadi Shakshuki, Acadia University, Canada

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3 Fully funded PhD positions in Software Technology at Radboud University, Netherlands
by Peter Achten 20 Dec '21

20 Dec '21

-------------------------------------------------------------------------------------- 3 Fully funded PhD positions in Software Technology at Radboud University, Netherlands -------------------------------------------------------------------------------------- In the Software Technology group at Radboud University in Nijmegen, Netherlands, we are looking for enthusiastic and outstanding Computer Science or Mathematics students with a strong background in at least one of the following areas: * programming languages * compiler technology * code generation * runtime systems * High-Performance-Computing * Parallel Computing to strengthen our group. Our key driving force is the desire to combine programming language research with compiler technology and code generation techniques for creating practically applicable software tools. Our credo lies in HP3 technology: combining High-Productivity, High-Portability, and High-Performance. Long-term projects driven by our group include the Clean project (clean.cs.ru.nl), the SaC project (www.sac-home.org) and the iTask system (clean.cs.ru.nl/ITasks). Our current focal points are: *Gradual Programming*, *Swarm Computing*, *Heterogeneous High- Performance Computing*, *Sustainable and Energy-Efficient Computing*. With *Gradual Programming*, we aim to combine the flexibility of rapid prototyping with the type safety of strongly typed programming languages. We look into a radically new approach towards typing programming languages for increased productivity, correctness and sustainability. Please contact Peter Achten (P.Achten(a)cs.ru.nl) for details. *Swarm Computing* refers to the idea of being able to, from a single source, perform programming, controlling, and computation on a dynamic and hybrid collection of computational units varying from CPUs, GPUs, FPGAs, TPUs, to IoT devices. Currently, we are particularly interested in Swarm Computing for sustainable IoT utilisation. Please contact Pieter Koopman (pieter(a)cs.ru.nl) for details. In *Heterogeneous High-Performance Computing*, we are interested in the generation of code for swarm computing systems aiming for unprecedented levels of efficiency in terms of both, runtime and energy efficiency. This includes mainstream accelerators such as GPUs and FPGAs as well as novel architectures such as Cerebras’ new architecture (www.cerebras.net) This work will contribute to the new TEN-X initiative (mission10-x.org) Please contact Sven-Bodo Scholz (SvenBodo.Scholz(a)ru.nl) for details. We offer: * a gross monthly salary starting from €2,434 in the first year, step-wise increasing to €3,111 in the fourth year. * a 4 year full-time contract, subject to a successful performance evaluation after 18 months. * a stimulating work environment with excellent Dual Career and Family Care Services. = How to apply = Applications should consist of a single pdf-file containing your CV, a cover letter explaining your motivation, and a letter of reference. We will consider applications as they arrive until the positions are filled. The deadline for applications is January 31 2022. Please send your application to: SvenBodo.Scholz(a)ru.nl.

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Package takeover request for oath
by Fumiaki Kinoshita 17 Dec '21

17 Dec '21

At the moment, oath is registered as a "reserved package name" (see https://mail.haskell.org/pipermail/libraries/2021-December/031524.html) and does not exist as an actual package. I'd like to upload a package with this name unless there's a specific reason why I should not. My Hackage username is FumiakiKinoshita. Best regards,

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install error: sym
by Gregory Guthrie 15 Dec '21

15 Dec '21

Seems like this is a package error? Sym\Perm\STAT.hs:13:8: error: File name does not match module name: Saw: `Sym.Perm.Stat' Expected: `Sym.Perm.STAT' Install log: PS C:\Users\guthrie\Desktop> cabal install sym Resolving dependencies... Build profile: -w ghc-8.10.2 -O1 In order, the following will be built (use -v for more details): - base-orphans-0.8.6 (lib) (requires download & build) - primitive-0.7.3.0 (lib) (requires download & build) - hashable-1.4.0.1 (lib) (requires download & build) - vector-0.12.3.1 (lib) (requires download & build) - sym-0.13.0 (lib) (requires download & build) Downloading base-orphans-0.8.6 Downloaded base-orphans-0.8.6 Downloading primitive-0.7.3.0 Starting base-orphans-0.8.6 (lib) Downloaded primitive-0.7.3.0 Downloading vector-0.12.3.1 Starting primitive-0.7.3.0 (lib) Downloaded vector-0.12.3.1 Downloading hashable-1.4.0.1 Downloaded hashable-1.4.0.1 Downloading sym-0.13.0 Downloaded sym-0.13.0 Building base-orphans-0.8.6 (lib) Building primitive-0.7.3.0 (lib) Installing base-orphans-0.8.6 (lib) Completed base-orphans-0.8.6 (lib) Starting hashable-1.4.0.1 (lib) Building hashable-1.4.0.1 (lib) Installing primitive-0.7.3.0 (lib) Completed primitive-0.7.3.0 (lib) Starting vector-0.12.3.1 (lib) Installing hashable-1.4.0.1 (lib) Building vector-0.12.3.1 (lib) Completed hashable-1.4.0.1 (lib) Installing vector-0.12.3.1 (lib) Completed vector-0.12.3.1 (lib) Starting sym-0.13.0 (lib) Building sym-0.13.0 (lib) Failed to build sym-0.13.0. Build log ( C:\Users\guthrie\AppData\Roaming\cabal\logs\ghc-8.10.2\sym-0.13.0-6a5a01f540d09f303c049bc421a706632878562d.log ): Preprocessing library for sym-0.13.0.. Building library for sym-0.13.0.. Sym\Perm\STAT.hs:13:8: error: File name does not match module name: Saw: `Sym.Perm.Stat' Expected: `Sym.Perm.STAT' | 13 | module Sym.Perm.Stat | ^^^^^^^^^^^^^ cabal.exe: Failed to build sym-0.13.0. See the build log above for details. Dr. Gregory Guthrie

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Error message??
by Gregory Guthrie 15 Dec '21

15 Dec '21

I don't understand the error here: -- ------------------------------------------ -- Find permutation by index iPerm :: Int -> [a] -> (Int,Int) iPerm k list = nPerm k $ length list where nPerm k n = divMod k (fact(n - 1)) -- indexPerm :: Int -> [a] -> [a] indexPerm _ [] = [] indexPerm g list = d :: indexPerm r (delete d list) -- line 19 *** where (q,r) = iPerm g list d = list !! q Adding a type signature for indexPerm changes the error (below), but seems to be the same basic issue. I thought I might need: indexPerm :: Eq a => Int -> [a] -> [a] to match the restriction on delete argument types, although I would have thought that would be inferred if needed, but it gives the same error message. ----------------------------------------------------------------------- Prelude> (compiling) [1 of 1] Compiling Main ( syntaxtest.hs, interpreted ) yntaxtest.hs:19:20: error: * Couldn't match expected type `indexPerm r (delete1 d1 list1)' with actual type `a' because type variables `indexPerm', `r', `delete1', `d1', `list1' would escape their scope These (rigid, skolem) type variables are bound by an expression type signature: forall (indexPerm :: * -> * -> *) r (delete1 :: * -> * -> *) d1 list1. indexPerm r (delete1 d1 list1) at syntaxtest.hs:19:25-51 * In the expression: d :: indexPerm r (delete d list) In an equation for `indexPerm': indexPerm g list = d :: indexPerm r (delete d list) where (q, r) = iPerm g list d = list !! q * Relevant bindings include d :: a (bound at syntaxtest.hs:21:10) list :: [a] (bound at syntaxtest.hs:19:13) indexPerm :: Int -> [a] -> [delete d list] (bound at syntaxtest.hs:18:1) | 19 | indexPerm g list = d :: indexPerm r (delete d list) | ^ | 19 | indexPerm g list = d :: indexPerm r (delete d list) | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Failed, no modules loaded. ----------------------------------------------------------------------- (error with the explicit type signature) syntaxtest.hs:19:20: error: * Couldn't match expected type `indexPerm r (delete d list)' with actual type `a' `a' is a rigid type variable bound by the type signature for: indexPerm :: forall a. Int -> [a] -> [a] at syntaxtest.hs:17:1-30 * In the expression: d :: indexPerm r (delete d list) In an equation for `indexPerm': indexPerm g list = d :: indexPerm r (delete d list) where (q, r) = iPerm g list d = list !! q * Relevant bindings include d :: a (bound at syntaxtest.hs:21:10) list :: [a] (bound at syntaxtest.hs:19:13) indexPerm :: Int -> [a] -> [a] (bound at syntaxtest.hs:18:1) | 19 | indexPerm g list = d :: indexPerm r (delete d list) | ^ | 19 | indexPerm g list = d :: indexPerm r (delete d list) | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Failed, no modules loaded. Gregory Guthrie

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Fully (UK Home) Funded PhD Positions in the Safety and Security of Advanced Systems Group (Exeter, UK, Deadline 2021-01-24)
by Achim D. Brucker 15 Dec '21

15 Dec '21

Several fully funded PhD scholarships for UK applicants are available 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), * specification-based testing, and * design and implementation of security architectures. This award provides annual funding to cover UK tuition fees and a tax-free stipend. For students who pay UK tuition fees the award will cover the tuition fees in full, plus at least £15,009 per year tax-free stipend. The studentship will be awarded on the basis of merit for 3.5 years of full-time study. Interested candidates should contact the potential supervisors 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 * Software Engineering for Security- or Safety-Critical Systems: https://www.exeter.ac.uk/study/funding/award/?id=4329 * Open Call: https://www.exeter.ac.uk/study/funding/award/?id=4343 The closing date for applications is midnight on the 24th of January 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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Postdoc position - hardware acceleration of Haskell
by Rob Stewart 14 Dec '21

14 Dec '21

Hi haskell-cafe, I have an opening for a postdoc position at Heriot-Watt University in Edinburgh, on hardware acceleration of functional programming languages. In particular, Haskell. Candidates should have a background in hardware design and FPGA programming. Hardware engineering experience should include circuit design, developing processor architectures, memory hierarchies and/or instruction sets. Candidates should have some understanding of functional programming. Programming language implementation experience is desirable, but not essential. The role will involve developing a special purpose processor for Haskell, aimed at outperforming the throughput and energy performance of CPUs. The project has close industry ties in Ireland and the Netherlands. It is a three year project, starting in May 2022. The HAFLANG project: https://haflang.github.io Job details and application form: https://enzj.fa.em3.oraclecloud.com/hcmUI/CandidateExperience/en/sites/CX/j… The application deadline is 28th February 2022. Contact the PI, Rob Stewart, with inquiries (R.Stewart(a)hw.ac.uk) Please share this widely. -- Rob Stewart Assistant Professor of Computer Science Heriot-Watt University, Edinburgh W: https://www.macs.hw.ac.uk/~rs46

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[CFP] Functional Conf 2022 online - have you got Haskell insights to share with the community?
by John Sinclair 14 Dec '21

14 Dec '21

Have you devised an innovative or novel application of Haskell? Have you solved a tricky problem using FP? This is a great opportunity to share what you've been working on. If it's related to functional programming, Functional Conf would love to hear from you! We are looking for deep technical topics related to Functional Programming. Learn more and submit your proposal here: https://confng.in/oVspOYAc <https://llink.to/?u=https:%2F%2Fsignal2domain.online%2Fclick%3Fredirect%3Dh…> Submissions close: 15 Jan 2022 Functional Conf is Asia's premiere functional programming conference. The event runs 24-26 March 2022 and due to COVID uncertainties will be held online. Over the course of 3 days, you'll get cutting edge insights from global thought leaders, practitioners and developers from prominent FP languages (this could be you!). At our last conference Edward Kmett who chairs the Haskell core libraries committee presented. The conference is designed to help attendees: - Understand the fundamental concepts of FP - Learn how others are leveraging FP to solve real world problems - Explore practical usages and gotchas in FP concepts from experts - Exchange real-world experience with your programing peers If you are just getting started with FP or work with it everyday, you'll love Functional Conf 2022! Here's a short video of past speakers sharing a little of their experience at Functional Conf: https://confng.in/EFX1sthg <https://llink.to/?u=https:%2F%2Fsignal2domain.online%2Fclick%3Fredirect%3Dh…> Submit your proposal here: https://confng.in/JzhW9cSX <https://llink.to/?u=https:%2F%2Fsignal2domain.online%2Fclick%3Fredirect%3Dh…> Hope to see you there! Best regards, John Sinclair and the Functional Conf Team

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ImplicitParams in GHC 9.0.1
by ☂Josh Chia (謝任中) 13 Dec '21

13 Dec '21

Hi, I have the following code that builds successfully with "stack build" under GHC 8.10.7 but fails to build under GHC 9.0.1: https://github.com/jchia/ip-bug The compiler is switched by commenting/uncommenting the compiler line in stack.yaml. GHC 9.0.1 gives me the error I paste at the end. Is this expected (maybe as part of "simplified subsumtion" in https://gitlab.haskell.org/ghc/ghc/-/wikis/migration/9.0#compiler-changes)? If so, how can the code be fixed? If not, is it a compiler bug? (This problem came up while using gi-gtk-3.0.38, where implicit params are used a lot). Josh /home/jchia/gh/ip-bug/src/Lib.hs:10:28: error: • Couldn't match type ‘(?self::Int) => Char’ with ‘Char’ Expected: Int -> Char -> Char Actual: Int -> ((?self::Int) => Char) -> Char • In the expression: foo In the expression: (let ?self = x in foo) :: Int -> Char -> Char In the expression: ((let ?self = x in foo) :: Int -> Char -> Char) x | 10 | bar x = ((let ?self = x in foo) :: Int -> Char -> Char) x | ^^^ /home/jchia/gh/ip-bug/src/Lib.hs:13:26: error: • Couldn't match type ‘(?self::Int) => Char’ with ‘Char’ Expected: Char -> Char Actual: ((?self::Int) => Char) -> Char • In the expression: foo x In the expression: let ?self = x in foo x In an equation for ‘baz’: baz x = let ?self = x in foo x | 13 | baz x = let ?self = x in foo x | ^^^^^

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DataKinds and Data.Char
by Olaf Klinke 13 Dec '21

13 Dec '21

Dear Café, Question: Is DataKinds promotion of Char values possible, and if yes, how? I want to define a data type of text where a certain character has special meaning. I could say: data SpecialText = SpecialText Char Text but it would be favourable if the type system forbids combining texts with distinct special characters. data SpecialText char = SpecialText Text Ideally, we could use DataKinds to specialize the char phantom type parameter to a promoted Char value, but neither 'x' nor ''x' is accepted by GHC, presumably for good reasons. After all, 'x' is syntactic sugar for the real constructor of a Char value (which is what? Data.Data.toConstr 'x' yields 'x'.) One certainly can define data types symbolizing selected single Char values to use as the phantom type, but that means the library author decides which Chars the user can declare as special. Thanks Olaf

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GHC debug plugin
by Daneel Yaitskov 13 Dec '21

13 Dec '21

Hi, I would like to enable stack traces at launch time and run program without HasCallStack overhead by default. I've got an idea to use GHC plugin which would duplicate all functions in modules with specified prefix. Duplicated functions should get disambiguating prefix (e.g. "debug") and HasCallStack constraint. Bodies of prefixed functions should be rewritten to use prefixed functions from matching modules (should be easy to do - hook just after renaming GHC phase when all names are fully qualified?). This way main function could choose "runLib" or "debugRunLib". Did anybody make something similar? -- Best regards, Daniil Iaitskov

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Re: [Haskell-cafe] Wiki account request
by howard.b.golden＠gmail.com 12 Dec '21

12 Dec '21

Hi Hyeon, I have created your Haskell wiki account. You should receive a temporary password by separate email. Please let me know if you have any problems. Regards, Howard On Mon, 2021-12-13 at 06:05 +0900, 김지현 wrote: > Hi folks, > > I'd like to create a new haskell wiki account with a username > "simnalamburt". At first, I tried to send an email to the "wiki- > account-request" mailing list as written in > https://wiki.haskell.org/index.php?title=Special:UserLogin, but I > couldn't find the mailing list. If that mailing list is gone, I think > the notice in the login page should be updated. > > If creating a wiki account takes a long time, can anyone do me a > favor? I just want to change the outdated link "Using haskell- > language-server with Vim or NeoVim." in the > https://wiki.haskell.org/Vim page to point to > https://haskell-language-server.readthedocs.io/en/latest/configuration.html… > . > > Best, > Hyeon Kim

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Priority queue benchmarks
by David Feuer 10 Dec '21

10 Dec '21

I've started working on performance of the venerable but somewhat neglected pqueue package. The changes I've made so far are pretty obviously good, and make a big difference in even the most informal testing. But to make decisions about smaller points, I really need benchmarks, and the package has none. Does anyone know of a benchmark suite for priority queues? One that includes algorithms that involve persistent queue use would be particularly desirable, but I'll take anything.

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Call for Workshop Proposals: ICFP 2022
by Ilya Sergey 08 Dec '21

08 Dec '21

CALL FOR WORKSHOP AND CO-LOCATED EVENT PROPOSALS ICFP 2022 27th ACM SIGPLAN International Conference on Functional Programming September 11 - 16, 2022 Ljubljana, Slovenia https://icfp22.sigplan.org/ The 27th ACM SIGPLAN International Conference on Functional Programming will be held in Ljubljana, Slovenia on September 11 - 16, 2022, with the option of virtual participation. ICFP provides a forum for researchers and developers to hear about the latest work on the design, implementations, principles, and uses of functional programming. Proposals are invited for workshops (and other co-located events, such as symposiums) to be affiliated with ICFP 2022 and sponsored by SIGPLAN. These events should be less formal and more focused than ICFP itself, include sessions that enable interaction among the attendees, and foster the exchange of new ideas. The preference is for one-day events, but other schedules can also be considered. The workshops are scheduled to occur on September 11th (the day before ICFP) and September 15-16th (the two days after ICFP). ---------------------------------------------------------------------- Submission details Deadline for submission: December 24, 2021 Notification of acceptance: January 10, 2022 Prospective organizers of workshops or other co-located events are invited to submit a completed workshop proposal form in plain text format to the ICFP 2022 workshop co-chairs (Arthur Azevedo de Amorim and Zoe Paraskevopoulou) via email to icfp-workshops-2022(a)googlegroups.com by December 24, 2021. (For proposals of co-located events other than workshops, please fill in the workshop proposal form and just leave blank any sections that do not apply.) Please note that this is a firm deadline. Organizers will be notified if their event proposal is accepted by January 10, 2022, and if successful, depending on the event, they will be asked to produce a final report after the event has taken place that is suitable for publication in SIGPLAN Notices. The proposal form is available at: http://www.icfpconference.org/icfp2022-files/icfp22-workshops-form.txt Further information about SIGPLAN sponsorship is available at: http://www.sigplan.org/Resources/Proposals/Sponsored/ ---------------------------------------------------------------------- Selection committee The proposals will be evaluated by a committee comprising the following members of the ICFP 2022 organizing committee, together with the members of the SIGPLAN executive committee. Workshop Co-Chair: Arthur Azevedo de Amorim (Boston University) Workshop Co-Chair: Zoe Paraskevopoulou (Northeastern University) General Chair: Andrej Bauer (University of Ljubljana) Program Chair: Zena Ariola (University of Oregon) ---------------------------------------------------------------------- Further information Any queries should be addressed to the workshop co-chairs (Arthur Azevedo de Amorim and Zoe Paraskevopoulou), via email to icfp-workshops-2022(a)googlegroups.com.

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