- Haskell-Cafe - Haskell.org

Postdoc at Inria/Irisa on translation validation from LiquidHaskell
by Ranjit Jhala 25 Feb '17

25 Feb '17

Hi all, Inria Project-team TEA is seeking a talented PhD with demonstrated experience in theory and implementation of refinement types in programming and automated verification and proof of programs. The aim of our post-doctoral project is to design a certified code generator from Liquid Haskell to verified, imperative and functional, compiler suites (CompCert, CakeML). We will start by initially focusing on first-order functions in the absence of dynamic memory management. In the spirit of Pnueli's translation validation principle, we will prove code generated from the code generator to obey program properties inferred from source programs, using refinement reflection. We will study extensions to hardware synthesis as well as dynamic memory management, higher-order functions, etc. For context, details, and application, please visit: https://www.inria.fr/ institut/recrutement-metiers/offres/post-doctorat/sejours- post-doctoraux/(view)/details.html?id=PGTFK026203F3VBQB6G68LONZ&LOV5 =4508&nPostingID=11123&nPostingTargetID=17708

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[Haskell-Cafe] Different memory profile in cabal project.
by Thomas Vanhelden 24 Feb '17

24 Feb '17

I have a (dummy) program that reads the contents of a file into a ByteString and then converts the ByteString to a Vector of Floats. To test the laziness of this program, I’ve taken a slice of the the Vector and printed it to the standard output. The program looks like this: import qualified Data.Vector.Unboxed as V import qualified Data.ByteString as BS import Data.Word import System.Environment import GHC.Int main = do [file] <- getArgs samples <- getSamplesFromFile file let slice = V.slice 0 50000 samples print slice getSamplesFromFile = fmap toVector . BS.readFile toVector :: BS.ByteString -> V.Vector Float toVector bs = vgenerate (fromIntegral (BS.length bs `div` 3)) $ \i -> myToFloat [BS.index bs (3*i), BS.index bs (3*i+1), BS.index bs (3*i+2)] where myToFloat :: [Word8] -> Float myToFloat = sum . map fromIntegral vgenerate n f = V.generate n (f . fromIntegral) So I compile this program and generate a memory profile via: ghc Main.hs -O2 -rtsopts -prof ./Main debug48.wav +RTS -hy hp2ps -e8in -c Main.hp ps2pdf Main.ps The file debug48.wav is a 12.9MB file. This is the result: If I now create a cabal project and add the exact same program as the main file by: mkdir testing cd testing cabal init add the program’s code to src/Main.hs add bytestring and vector to the build dependencies (in testing.cabal) add -O2 -rtsopts -prof to the ghc-options (in testing.cabal) cabal install testing debug48.wav +RTS -hy hp2ps -e8in -c testing.hp ps2pdf testing.ps This is the result: How can there be such a big difference in memory usage, just by the code being part of a cabal project?

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Working at Chordify? Working with Music. Coding in Haskell.
by Bas de Haas 24 Feb '17

24 Feb '17

Dear Haskellers, Chordify is hiring! Chordify is a young and fast growing music e-learning platform that helps musicians to play their favorite music. We automatically analyse the chords of a piece of music and display them in an intuitive player. Try it yourself at: https://chordify.net/ . The cool thing is: our backend has been written almost exclusively in Haskell. We hope to broaden our team with a researcher and a developer. We are looking for people who are pro-active, independent, and creative to improve Chordify. * We offer a digital signal processing researcher position in which you can prototype, evaluate, and deploy new algorithms that form the core of Chordify. * We also offer a (front-end) developer position in which you can improve the Chordify user experience, launch new ideas, write Haskell, and have thousands of users use your code every day. If you are interested in working at Chordify, you can find the details here: https://chordify.homerun.co/ All the best, Bas de Haas

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Extensions to Haskell 98 in the GHC Prelude?
by Dylan Thurston 24 Feb '17

24 Feb '17

Pardon me if this is a stupid/frequently asked question... The GHC Prelude has some extensions to the Prelude in Haskell 98 or Haskell 2010. For instance, it has the Applicative type class, whose bindings overlap with some old code of mine. Where are these non-standard extensions documented? The Applicative class is documented at https://downloads.haskell.org/~ghc/latest/docs/html/libraries/base-4.9.0.0/… but it's not picked out as something non-standard. I didn't find it documented where I would have expected in the GHC docs at https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/bugs.html#h… nor did I see a way to get a standards-compliant prelude? In this particular case I'll probably rework my code, as Applicative seems like a reasonable core addition. (I am a little annoyed that it uses so many short infix operators; I was using (*>).) I'm just surprised not to see it documented anywhere. Thanks, Dylan Thurston

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Read my thesis draft on Backpack!
by Edward Z. Yang 24 Feb '17

24 Feb '17

Hello all, I have finished a draft of my thesis on Backpack, a new module system for Haskell (building on top of the work of Scott Kilpatrick et al). This thesis also doubles as the definitive manual on Backpack, which will be released with the upcoming GHC 8.2. I've posted a copy of the draft here: https://github.com/ezyang/thesis/releases and I would love it if you took a look at it, gave it a read perhaps, and told me about anything that was unclear or not well explained. You can file an issue on the GitHub, or shoot me an email or tweet. Looking forward to your comments. Thanks, Edward

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ghc on xeon phi?
by Johannes Waldmann 24 Feb '17

24 Feb '17

Dear Cafe - would a program compiled by ghc, or ghc itself, run as-is on Intel Xeon Phi (KNL)? I found this reference http://stackoverflow.com/questions/22253311/running-haskell-on-xeon-phi but it seems to be about the pre-KNL version. Thanks - J.

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Trends in Functional Programming in Education ITFPIE) 2017, call for papers
by Simon Thompson 23 Feb '17

23 Feb '17

TFPIE 2017 Trends in Functional Programming in Education, 2017 The sixth workshop on Trends in Functional Programming in Education, 2017, which is to be held on the Canterbury campus of the University of Kent on Thursday, 22 June, following the 2017 TFP meeting on 19–21 June. TFPIE workshops have previously been held in St Andrews, Scotland (2012), Provo Utah, USA (2013), Soesterberg, The Netherlands (2014), and Sophia-Antipolis, France (2015), College Park, USA (2016). The goal of TFPIE is to gather researchers, teachers and professionals that use, or are interested in the use of, functional programming in education. TFPIE aims to be a venue where novel ideas, classroom-tested ideas and work-in-progress on the use of functional programming in education are discussed. The one-day workshop will foster a spirit of open discussion by having a review process for publication after the workshop. The program chair of TFPIE 2017 will screen submissions to ensure that all presentations are within scope and are of interest to participants. After the workshop, presenters will be invited to submit revised versions of their articles for publication in the journal Electronic Proceedings in Theoretical Computer Science (EPTCS). Call for papers TFPIE 2017 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. Submission Potential presenters are invited to submit an extended abstract (4-6 pages) or a draft paper (up to 16 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=tfpie2017 After the workshop, presenters will be invited to submit (a revised version of) their article for review. The PC will select the best articles for publication in the journal Electronic Proceedings in Theoretical Computer Science (EPTCS). Articles rejected for presentation and extended abstracts will not be formally reviewed by the PC. Programme committee Dr Laura Castro, University of A Coruña Prof Ralf Lämmel, University of Koblenz-Landau Dr Elena Machkasova, University of Minnesota, Morris Prof Michel Mauny, Inria, Paris Dr Jeremy Singer, University of Glasgow Prof Simon Thompson, University of Kent (chair) Important dates Submissions of draft papers: 10 May, 2017 Notification: 17 May, 2017 Registration: 11 June, 2017 Workshop: 22 June 2017 Submission for formal review: 18 August, 2017 Notification of acceptance: 6 October, 2017 Camera ready paper: 3 November, 2017 Simon Thompson | Professor of Logic and Computation School of Computing | University of Kent | Canterbury, CT2 7NF, UK s.j.thompson(a)kent.ac.uk | M +44 7986 085754 | W www.cs.kent.ac.uk/~sjt

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-Werror -Woverlapping-patterns -fglasgow-exts ?
by Johannes Waldmann 23 Feb '17

23 Feb '17

Dear Cafe, I want to chase overlapping patterns in a larger code base. So I use -Werror -Woverlapping-patterns . But the code also needs -fglasgow-exts and this makes compilation stop right at the beginning, with "warning: -fglasgow-exts is deprecated: ..." which will be turned into an error because of -Werror -Wno-warnings-deprecations does not help, apparently that warning is not a deprecation. Is there a way to get -Werror for specific warnings? - J.

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Size-indexed monoids
by Kosyrev Serge 23 Feb '17

23 Feb '17

Good day! What is the proper type class for stronger-typed (size-indexed) monoids: - that is, monoids carrying their "size" in the type - preferably as GHC.TypeLits.Nat - preferably on Hackage ? I'm quite prepared to the idea that a monoid is an entirely wrong abstraction, from a category-theoretic standpoint, so I would gladly learn of a better one : -) Use case: > {-# LANGUAGE DataKinds, GADTs, KindSignatures, TypeOperators, UnicodeSyntax, StandaloneDeriving #-} > > module Understanding.Types where > > import GHC.TypeLits > > data T (depth ∷ Nat) p where > TZ ∷ T 0 p > TS ∷ (Show p, CmpNat (m + 1) n ~ EQ) ⇒ > { payload ∷ p > , next ∷ T m a } → T n a > deriving instance Show p ⇒ Show (T d p) > > instance Monoid (T d p) where > mempty = TZ > mappend TZ TZ = TZ > mappend TZ t@(TS _ _) = t > mappend t@(TS _ _) TZ = t > mappend tl@(TS pl nl) tr = TS pl $ mappend nl tr As it is, even the mempty case rejects such a blatant violation of polymorphism, since `T 0 p` cannot unify with `T n p`. So, ideally (I think), I would like something like this: > class TypedMonoid a where > tmempty ∷ a 0 > tmappend ∷ a n → a m → a (n + m) -- с уважениeм / respectfully, Косырев Сергей -- “Most deadly errors arise from obsolete assumptions.” -- Frank Herbert, Children of Dune

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CFP: International Workshop on OCL and Textual Modeling (OCL 2017)
by Achim D. Brucker 23 Feb '17

23 Feb '17

(Apologies for duplicates) CALL FOR PAPERS 17th International Workshop on OCL and Textual Modeling Co-located with STAF 2017 SOFTWARE TECHNOLOGIES: APPLICATIONS AND FOUNDATIONS July 20, 2017, Marburg, Germany http://oclworkshop.github.io Modeling started out with UML and its precursors as a graphical notation. Such visual representations enable direct intuitive capturing of reality, but they have weaknesses: for example, detailed visual representations bear the risk of becoming overcrowded faster than textual models and some of the visual features lack the level of precision required to create complete and unambiguous specifications. These weaknesses of graphical notations encouraged the development of text-based modeling languages that either integrate with or replace graphical notations for modeling. Typical examples of such languages are OCL, textual MOF, Epsilon, and Alloy. Textual modeling languages have their roots in formal language paradigms like logic, programming and databases. The goal of this workshop is to create a forum where researchers and practitioners interested in building models using OCL or other kinds of textual languages can directly interact, report advances, share results, identify tools for language development, and discuss appropriate standards. In particular, the workshop will encourage discussions for achieving synergy from different modeling language concepts and modeling language use. The close interaction will enable researchers and practitioners to identify common interests and options for potential cooperation. ## Topics of interest Topics of interest include (but are not limited to): - Mappings between textual modeling languages and other languages/formalisms - Algorithms, evaluation strategies and optimizations in the context of textual modeling languages for: - validation, verification, and testing, - model transformation and code generation, - meta-modeling and DSLs, and - query and constraint specifications - Alternative graphical/textual notations for textual modeling languages - Evolution, transformation and simplification of textual modeling expressions - Libraries, templates and patterns for textual modeling languages - Tools that support textual modeling languages (e.g., verification of OCL formulae, runtime monitoring of invariants) - Complexity results for textual modeling languages - Quality models and benchmarks for comparing and evaluating textual modeling tools and algorithms - Successful applications of textual modeling languages - Case studies on industrial applications of textual modeling languages - Experience reports: - usage of textual modeling languages and tools in complex domains, - usability of textual modeling languages and tools for end-users - Empirical studies about the benefits and drawbacks of textual modeling languages - Innovative textual modeling tools - Comparison, evaluation and integration of modeling languages - Correlation between modeling languages and modeling tasks This year, we particularly encourage submissions describing applications and case studies of textual modeling as well as test suites and benchmark collections for evaluating textual modeling tools. ## Venue This workshop will be organized as a part of STAF 2017 Conferenze in Marburg, Germany. It was previously organized as part of the MODELS conference. Similar to its predecessors , the workshop addresses both people from academia and industry . The aim is to provide a forum for addressing integration of OCL and other textual modeling languages , as well as tools for textual modeling , and for disseminating good practice and discussing the new requirements for textual modeling . ## Workshop Format The workshop will include short (about 15 min) presentations, parallel sessions of working groups, and sum-up discussions. ## Submissions Two types of papers will be considered: * Short contributions (between 6 and 8 pages) describing new ideas, innovative tools or position papers. * Full papers (between 12 and 16 pages). in LNCS format. Submissions should be uploaded to [EasyChair](https://easychair.org/conferences/?conf=ocl17). The program committee will review the submissions (minimum 2 reviews per paper, usually 3 reviews) and select papers according to their relevance and interest for discussions that will take place at the workshop. Accepted papers will be published online in a post-conference edition of [CEUR](http://www.ceur-ws.org). ## Important Dates - Submission of papers: April 28, 2017 - Notification: May 25, 2017 - Workshop date: July 20, 2017 -- Dr. Achim D. Brucker | Software Assurance & Security | University of Sheffield https://www.brucker.ch | https://logicalhacking.com/blog @adbrucker | @logicalhacking

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