December 2014 - Haskell-Cafe

Haskell 2014
by Дмитрий 02 Dec '14

02 Dec '14

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10 PhD studentships in Nottingham
by Graham Hutton 02 Dec '14

02 Dec '14

Dear all, The School of Computer Science in Nottingham is advertising 10 fully-funded PhD studentships. Applicants in the area of the Functional Programming lab (fp.cs.nott.ac.uk) are encouraged! If you are interested in applying, please contact a potential supervisor in the FP lab prior to submitting your application: Thorsten Altenkirch - constructive logic, proof assistants, homotopy type theory, category theory, lambda calculus. Venanzio Capretta - type theory, mathematical logic, corecursive structures, proof assistants, dependently-typed programming. Graham Hutton - not taking on any new students this year. Henrik Nilsson - functional reactive programming, modelling and simulation, domain-specific languages, probabilistic languages. Best wishes, Graham +-----------------------------------------------------------+ 10 Fully-Funded PhD Studentships School of Computer Science University of Nottingham, UK http://tinyurl.com/ten-phds Applications are invited for up to ten fully-funded PhD studentships in the School of Computer Science at the University of Nottingham, starting on 1st October 2015. The topics for the studentships are open, but should relate to the interests of one of the School’s research groups: Agents Lab; Automated Scheduling, Optimisation and Planning; Computer Vision Lab; Functional Programming Lab; Intelligent Modelling and Analysis; Mixed Reality Lab; Networked Systems. The studentships are for three years and include a stipend of £13,863 per year and tuition fees, and are available to students of any nationality. Applicants are normally expected to have a first-class Masters or Bachelors degree in Computer Science or a related discipline, and must obtain the support of a potential supervisor in the School prior to submitting their application. Initial contact with supervisors should be made at least two weeks prior to the closing date for applications. Informal enquiries may be addressed to <Christine.Fletcher(a)nottingham.ac.uk>. To apply, please submit the following items by email to the above address: (1) a brief covering letter that describes your reasons for wishing to pursue a PhD, your proposed research area and topic, and the name of a potential supervisor; (2) a copy of your CV, including your actual or expected degree class(es), and results of all University examinations; (3) an example of your technical writing, such as a project report or dissertation; (4) contact details for two academic referees. Closing date for applications: 14th January 2015 +-----------------------------------------------------------+ This message and any attachment are intended solely for the addressee and may contain confidential information. If you have received this message in error, please send it back to me, and immediately delete it. Please do not use, copy or disclose the information contained in this message or in any attachment. Any views or opinions expressed by the author of this email do not necessarily reflect the views of the University of Nottingham. This message has been checked for viruses but the contents of an attachment may still contain software viruses which could damage your computer system, you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation.

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Using ghc-mod with FFI
by Dan Piponi 01 Dec '14

01 Dec '14

In my code I have this line: foreign import ccall "set_num_states" setNumStates :: Int -> IO () I can build my project using cabal and have an appropriate "c-sources:" line. But when I use ghc-mod check (eg. from " ghc-mod-5.2.0.0", and launched from Syntastic) it complains: "ghc-mod: ByteCodeLink: can't find label During interactive linking, GHCi couldn't find the following symbol: set_num_states" How should I be checking my code? -- Dan

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New Functional Programming Job Opportunities
by Functional Jobs 01 Dec '14

01 Dec '14

Here are some functional programming job opportunities that were posted recently: Scala Developer at Mediative http://functionaljobs.com/jobs/8767-scala-developer-at-mediative Cheers, Sean Murphy FunctionalJobs.com

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Re: [Haskell-cafe] Haskell 2014
by Roman Cheplyaka 01 Dec '14

01 Dec '14

The language («GHC Haskell») is evolving quite rapidly, it's just no-one is really interested in maintaining the standard anymore. I don't think it should disappoint you, unless you're a language researcher or compiler writer. On 30/11/14 14:29, Dmitry wrote: > Thanks for the answer, > > it's sad. > Even C++ now gets new releases every several years. > > Does anybody feel like the language is surpassed by other languages, for > example F#? > > > 30.11.2014, 17:46, "Roman Cheplyaka" <roma(a)ro-che.info>: >> >> On 30/11/14 04:03, Дмитрий wrote: >> >> Hi everyone, >> >> I couldn't find when haskell 2014 standard will come out. Is >> there any >> information about it? >> Somewhere I read that a new standard should be released each year >> but it >> seems not to be true nowadays >> >> There's no-one working on the Haskell standard, to the best of my >> knowledge. So no, it probably won't come out. >> >> Roman >>

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ANN: Opaleye -- SQL-generating embedded domain specific language for Postgres
by Tom Ellis 01 Dec '14

01 Dec '14

I am pleased to announce the public release of Opaleye, now available on Hackage and at GitHub: http://hackage.haskell.org/package/opaleye https://github.com/tomjaguarpaw/haskell-opaleye Opaleye is a Haskell library which provides an SQL-generating embedded domain specific language for targeting Postgres. You need Opaleye if you want to use Haskell to write typesafe and composable code to query a Postgres database. Opaleye allows you to define your database tables and write queries against them in Haskell code, and aims to be typesafe in the sense that if your code compiles then the generated SQL query will not fail at runtime. A wide range of SQL functionality is supported including inner and outer joins, restriction, aggregation, distinct, sorting and limiting, unions and differences. Facilities to insert to, update and delete from tables are also provided. Code written using Opaleye is composable at a very fine level of granularity, promoting code reuse and high levels of abstraction. For further information please refer to the README and tutorials: https://github.com/tomjaguarpaw/haskell-opaleye/blob/master/README.md https://github.com/tomjaguarpaw/haskell-opaleye/blob/master/Doc/Tutorial/Tu… https://github.com/tomjaguarpaw/haskell-opaleye/blob/master/Doc/Tutorial/Tu… I would be happy to answer any questions anyone might have about this library. Tom

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Passionate About Using Haskell?
by jonathan.erwin 01 Dec '14

01 Dec '14

Dear Haskellers, I am looking for developers passionate about using Haskell on the job to join my engineering team based in Norwich, Norfolk. About Us: · Inchora Ltd (http://www.inchora.com) is privately funded with a clear growth plan for the next 5 years. Our business model revolves around developing products and distributing them with our own marketing assets. · Our products are diverse and serve multiple industries including utilities, local government, online marketing and finance. You will be working across them all. The Role: · We're looking for experienced developers who have previously worked on commercial software projects (even if they were written in C++ or Java...). · Work from the Norwich office on a permanent basis developing applications using Haskell, MongoDB, Heroku and other goodies. · Help document and subsequently unify the code base of at least 5 different product suites all suffering from delirious imperative code. · Salary of £45,000-£60,000 (plus bonus) depending on experience. The Perks · Norfolk is a real ale Mecca. Seriously there is so much good beer we have a festival every October. · We love FP! We want to show the world what applications written in Haskell can do. · Build your own products or tinker with them in our lab (coming 2015). If it's a great idea, we'll back it with real money as part of our accelerator programme. Any questions? Ready to join? My number is below. Give me a ring! Sincerely, Jonathan Erwin Chief Technical Officer M: 07833 254186 | DDI: 0845 6432371 [inchora-logo-email]<http://www.inchora.com/> Inchora Limited - Quatro House, Lyon Way, Frimley, Surrey, GU16 7ER www.inchora.com<http://www.inchora.com/> | 01276 804400<tel:+441276804400> This email and any attachments may be legally privileged and are confidential, protected by copyright and for the addressee only. We have taken reasonable steps to reduce risks against viruses but cannot accept liability for any damages sustained as a result of this transmission. If you are not the intended receiver, any reading, copying or transmission of this email is prohibited. Please tell us by replying to this email and then delete the email from your system. Thank you.

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installation problems: wx, phooey, checkers
by Jeffrey Brown 01 Dec '14

01 Dec '14

I believe I have wxWidgets installed, because when I go to the demos/ or samples/ subfolders of ~/wxWidgets-3.0.2/build-cocoa-debug/, I can run the apps. Now I want to install the phooey library for Haskell. When I try, I am warned that some things will be broken, so I unregister them and then cabal install them all at once. (The complete output from my session with cabal appears below.) I run cabal from ~/wxWidgets, because that folder contains the files wx-config-inplace.in wx-config.in and I know cabal wants wx-config. The two errors I get: wx-config is not found checkers does not install I am left stumped. Thanks for your help. -------------------- jefferys-mbp:~ jbb$ cd wxWidgets-3.0.2/ jefferys-mbp:wxWidgets-3.0.2 jbb$ cabal install phooey Resolving dependencies... In order, the following would be installed: mtl-1.1.1.1 (latest: 2.2.1) (new version) parsec-3.1.7 (reinstall) changes: mtl-2.2.1 -> 1.1.1.1 reactive-0.5.0.1 (latest: 0.11.5) (new package) wxdirect-0.91.0.0 (reinstall) wxc-0.91.0.0 (new package) wxcore-0.91.0.0 (new package) wx-0.91.0.0 (new package) phooey-2.0.0.1 (new package) cabal: The following packages are likely to be broken by the reinstalls: tidal-0.4.21 network-uri-2.6.0.1 threepenny-gui-0.5.0.0 hmt-0.15 Use --force-reinstalls if you want to install anyway. jefferys-mbp:wxWidgets-3.0.2 jbb$ ghc-pkg unregister tidal jefferys-mbp:wxWidgets-3.0.2 jbb$ ghc-pkg unregister threepenny-gui jefferys-mbp:wxWidgets-3.0.2 jbb$ ghc-pkg unregister network-uri jefferys-mbp:wxWidgets-3.0.2 jbb$ ghc-pkg unregister hmt jefferys-mbp:wxWidgets-3.0.2 jbb$ cabal install tidal network-uri threepenny-gui hmt phooey Resolving dependencies... Configuring checkers-0.1.4... Configuring network-uri-2.6.0.1... Configuring hmt-0.15... Configuring wxc-0.91.0.0... Building network-uri-2.6.0.1... Building checkers-0.1.4... Building hmt-0.15... Failed to install checkers-0.1.4 Last 10 lines of the build log ( /Users/jbb/.cabal/logs/checkers-0.1.4.log ): at src/Test/QuickCheck/Instances/Num.hs:23:12-49 Possible fix: add (Eq a) to the context of the type signature for nonZero :: (Num a, Arbitrary a) => Gen a -> Gen a In the first argument of ‘satisfiesM’, namely ‘(/= 0)’ In the expression: satisfiesM (/= 0) (if (s == 0) then (resize 1 g) else g) In the first argument of ‘sized’, namely ‘(\ s -> satisfiesM (/= 0) (if (s == 0) then (resize 1 g) else g))’ Failed to install wxc-0.91.0.0 Last 10 lines of the build log ( /Users/jbb/.cabal/logs/wxc-0.91.0.0.log ): [1 of 1] Compiling Main ( /var/folders/q1/2_cf13z53tg__sqdk7v8ycgm0000gn/T/wxc-0.91.0.0-41510/wxc-0.91.0.0/Setup.hs, /var/folders/q1/2_cf13z53tg__sqdk7v8ycgm0000gn/T/wxc-0.91.0.0-41510/wxc-0.91.0.0/dist/setup/Main.o ) Linking /var/folders/q1/2_cf13z53tg__sqdk7v8ycgm0000gn/T/wxc-0.91.0.0-41510/wxc-0.91.0.0/dist/setup/setup ... Error: wx-config not found, please install wx-config before installing wxc Installed network-uri-2.6.0.1 Configuring threepenny-gui-0.5.0.0... Building threepenny-gui-0.5.0.0... Installed threepenny-gui-0.5.0.0 Installed hmt-0.15 Configuring tidal-0.4.21... Building tidal-0.4.21... Installed tidal-0.4.21 Updating documentation index /Users/jbb/Library/Haskell/share/doc/index.html cabal: Error: some packages failed to install: checkers-0.1.4 failed during the building phase. The exception was: ExitFailure 1 phooey-2.0 depends on wxc-0.91.0.0 which failed to install. reactive-0.9.3 depends on checkers-0.1.4 which failed to install. wx-0.91.0.0 depends on wxc-0.91.0.0 which failed to install. wxc-0.91.0.0 failed during the configure step. The exception was: ExitFailure 1 wxcore-0.91.0.0 depends on wxc-0.91.0.0 which failed to install.

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Haskell in the "Enterprise"
by gonzaw 01 Dec '14

01 Dec '14

Hi. I've been wondering if there are any plans or projects to bring Haskell to the "enterprise" ecosystem An by this I mean allowing applications made in Haskell (and other languages) to be integrated in a distributed fashion, easily being able to integrate different systems (DBMSs, web services, etc), etc. For example, creating an ESB in Haskell to allow easier integration of distributed applications. We all worked (or know someone who worked) with huge Java/IBM/etc enterprise systems, and know how clunky the experience was. Being able to include Haskell in this ecosystem would be so refreshing. I was also wondering if there is any research going on on how to apply the mathematical concepts and FP principles behind Haskell to these enterprise constructs. For instance, how to apply FP and category theory to Enterprise Application Integration to make scalable, robust and composable systems that are actually easy to use and discover. For example, I always had this idea of having "pure Web Services" and "effectful Web Services" as different protocols that can be used in different ways depending on the service being provided. Or maybe allowing functions to be passed as parameters in web services, by defining a small typed lambda calculus that can be serialized to XML and passed in a SOAP message (with the appropriate interpreters in the client+server). The ideas never went beyond that, but they sparked my interest in this sort of thing. To start somewhere, are there any Haskell libraries with Web Service support? Like a WS client tools (SOAP messaging DSL + WSDL import tool)? Or a haskell library that allows one to provide web services (and maybe provide the WS-* extensions)? -- View this message in context: http://haskell.1045720.n5.nabble.com/Haskell-in-the-Enterprise-tp5761538.ht… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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Kind product
by Gautier DI FOLCO 01 Dec '14

01 Dec '14

Hello all, I have the following code: {-# LANGUAGE NoImplicitPrelude #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE KindSignatures #-} {-# LANGUAGE DataKinds #-} {-# LANGUAGE PolyKinds #-} data Branch = Left | Right type family Product (v :: Branch) (a :: k) (b :: k) :: k where Product Left l r = l Product Right l r = r My goal is to have a thing like that: type family Product (v :: Branch) (a :: k1) (b :: k2) :: (Either k1 k2) where Is it possible to do such a thing? If not I can find a solution with Kind families/Kind pattern matching, but I don't think that exists, am I wrong? Thanks in advance for your help, Regards.

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