- Haskell-Cafe - Haskell.org

In case there are some other Haskellers around Eindhoven, NL
by Damian Nadales 20 Feb '17

20 Feb '17

On a very unmemorable day, lost somewhere in a province of the Netherlands, a new Haskell meetup has been born http://meetu.ps/c/32F0Z/tJxcH/f Best, Damian.

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Selective deriving
by Rui Azevedo 20 Feb '17

20 Feb '17

Hi! I don't know if there is some extension that already does this, or any other method of doing it. My search on deriving ghc mechanisms and extensions gave me no satisfactory results. the point is to have some "help" on derivation or some sort of derivation. actual derivation schema seems to require that all members (constructor arguments) instantiate the deriving class. This is the way of doing it for classes like Eq, works for Show and Ord but eventually it is a very strong requirement even for Eq sometimes. Of course I can do a manual derivation to state something else, and that sometimes can be frustrating because the derivations are way trivial and susceptible of automation. There is no fancy things added, its all standard haskell, user could laboriously type this. As an alternate derivation mechanism i seek selective deriving, like this: class Named o where name::o->String data A = A String deriving (Show) instance Named A where name="Object" till now just normal derivation data B = B A Int deriving (Show) extending (Named) the mechanism on extending requires that one and only one of the type constructor's direct arguments instantiates the class. this avoids the C++ diamond inheritance problem, user can recur on manual derivation. this will generate the code: instance Named B where name (B a _)=name a alternative can be: extending (Named A,...) this latter form is rater interesting as it cuts down the implementation boilerplate and still avoid the diamond problem even if multiple members instantiate the same class Are already any extension doing this? Can i achieve the same result by other forms? What is the best way to implement this thing? plug-ins seem not to be able to change syntax (right?) I've also looked at -F -pgmF options to use a preprocessor... can a preprocessor insert code to reference the original line numbers, just because messing with line numbers will make this unusable. regards rui

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AMMCS-2017 call for submissions
by Jacques Carette 19 Feb '17

19 Feb '17

Applied Mathematics, Modeling and Computational Science (AMMCS-2017) Waterloo, Ontario, Canada August 20-25, 2017 Minisymposium: Symbolic Methods in Code Generation and Programming Languages (ID: SS-SMCGPL; http://www.ammcs2017.wlu.ca/special-sessions/smcgpl/) Symbolic Methods in Code Generation and Programming Languages Symbolic methods are increasingly finding a wide variety of applications in and around programming languages. Starting from their immensely successful use in generation of numerical codes, their applicability is widening to both code analysis (often through abstract interpretation) and even in certain phases of compilers themselves, as exemplified in recent probabilistic programming languages. This session will bring together experts in symbolic computation along with programming languages experts to exchange ideas on the state of the art in this domain. Abstracts are being accepted for special sessions, contributed sessions, and poster presentations. All participants should submit their abstracts online via the AMMCS-2017 Management System at http://www.ammcs2017.wlu.ca/submit-abstracts/ Due: March 15, 2017 SS-SMCGPL Organizers: Jacques Carette (McMaster University), Eugene Zima (Wilfrid Laurier University) About AMMCS =========== AMMCS-2017 is an interdisciplinary international conference in a series of AMMCS meetings held in Waterloo, Ontario, Canada. The AMMCS Conference Series aims at promoting interdisciplinary research and collaboration involving mathematical and computational sciences within a larger international community, and highlighting recent advances in Applied Mathematics, Modeling and Computational Science (AMMCS). In 2017 the conference will be held in August (August 20-25, 2017). From its inception this conference series has been organized in cooperation with AIMS and SIAM. The conference provides a unique opportunity for in-depth technical discussions and exchange of ideas in all areas involving mathematical and computational sciences, modeling and simulation, as well as their applications in natural and social sciences, engineering and technology, industry and finance. It offers to researchers, industrialists, engineers and students to present their latest research, to interact with the experts in the field, and to foster interdisciplinary collaborations required to meet the challenges of modern science, technology, and society.

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QuickCheck and State monad
by George Boulougaris 19 Feb '17

19 Feb '17

Hello, I have written a Haskell module that contains functions that operate on some state. Let's say that the code looks like this (the actual functions may return an actual result instead of `()`, but this is irrelevant to the question): data StateContext = StateContext { -- some records } handleEventA :: EventA -> State StateContext () handleEventB :: EventB -> State StateContext () handleEventC :: EventC -> State StateContext () As you can imagine the behavior of each function depends on the current state. For example `handleEventA >> handleEventB` will not produce the same result as `handleEventB >> handleEventA`. So I have several HUnit tests that verify the behavior of each function at several states. But now I would like to write more tests, that exercise all functions at all possible states (the number of states is finite). Writing them with HUnit would be quite labor-itensive, so I thought that using QuickCheck might be helpful in that case (I have only used it before for trivial functions). But I cannot see which properties should I test, or what kind of data should the test generate. I suspect that the test should generate random sequence of events (e.g. `handleEventB >> handleEventC >> handleEventA` etc), but I cannot see what properties should be satisfied. Thanks

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[ANN] marvin-0.1.0, a Haskell framework for writing chat bots
by Justus Adam 19 Feb '17

19 Feb '17

Hello Haskell enthusiasts, For a couple of months now I’ve been working on a framework for writing chat bots in Haskell. The project is very heavily inspired by Hubot (https://hubot.github.com/ <https://hubot.github.com/>) and for the most part mimics its API. However it provides all the nice Haskell features, such as type safety and running as compiled code, rather than interpreted. If you’re curious check it out, I’d love some feedback. (Verbose) Documentation: http://marvin.readthedocs.io <http://marvin.readthedocs.io/> Package: https://hackage.haskell.org/package/marvin <https://hackage.haskell.org/package/marvin> Source code repository: https://github.com/JustusAdam/marvin <https://github.com/JustusAdam/marvin> Suggestions and issues: https://github.com/JustusAdam/marvin/issues <https://github.com/JustusAdam/marvin/issues> Regards, Justus

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ThEdu'17: Call for Extended Abstracts & Demonstrations
by Achim D. Brucker 18 Feb '17

18 Feb '17

(Apologies for duplicates) Call for Extended Abstracts & Demonstrations ThEdu'17 Theorem proving components for Educational software http://www.uc.pt/en/congressos/thedu/thedu17 at CADE 26 International Conference on Automated Deduction 6-11 August 2017 Gothenburg, Sweden http://www.cade-26.info/ ThEdu'17 Scope Computer Theorem Proving is becoming a paradigm as well as a technological base for a new generation of educational software in science, technology, engineering and mathematics. The workshop brings together experts in automated deduction with experts in education in order to further clarify the shape of the new software generation and to discuss existing systems. Topics of interest include: * methods of automated deduction applied to checking students' input; * methods of automated deduction applied to prove post-conditions for particular problem solutions; * combinations of deduction and computation enabling systems to propose next steps; * automated provers specific for dynamic geometry systems; * proof and proving in mathematics education. Important Dates Extended Abstracts: 18 June 2017 Author Notification: 2 July 2017 Final Version: 16 July 2017 Workshop Day: 6 August 2017 Submission Interested researchers are invited to submit extended abstracts and system descriptions. Both kinds of submissions should be approximately 5 pages in length and present original unpublished work not submitted elsewhere. Submission is in PDF format via easychair, https://easychair.org/conferences/?conf=thedu17 formatted according to http://www.easychair.org/publications/easychair.zip The extended abstracts and system descriptions will be made available online. At least one author is expected to presents his/her submission at ThEdu'17. Joint publication in companion with other CADE26 events is under consideration (as a volume in the EPiC Series in Computing). Program Committee Francisco Botana, University of Vigo at Pontevedra, Spain Achim D. Brucker, University of Sheffield, United Kingdom Filip Maric, University of Belgrade, Serbia Walther Neuper, Graz University of Technology, Austria (co-chair) Pavel Pech , University of South Bohemia, Czech Republic Pedro Quaresma, University of Coimbra, Portugal (co-chair) Vanda Santos, CISUC, Portugal Wolfgang Schreiner, Johannes Kepler University, Austria Burkhart Wolff, University Paris-Sud, France -- Dr. Achim D. Brucker | Software Assurance & Security | University of Sheffield https://www.brucker.ch | https://logicalhacking.com/blog @adbrucker | @logicalhacking

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Getting a rewrite rule to fire
by Clinton Mead 18 Feb '17

18 Feb '17

Basically, I want to rewrite `g (f x)` with `h x` where it's valid to do so (i.e. appropriate instances of `h` exist). The code I've put below is a silly example just to illustrate the issue. I guess the tricky thing is that whether the rewrite rule can fire depends on the result of `g (f x)`, not just x itself. Does anyone know how to adjust this so the rewrite rule fires? {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeApplications #-} module Main where data D a {-# INLINE [1] f #-} f :: a -> D a f = undefined type family T a type instance T Char = Int {-# INLINE [1] g' #-} g' :: (G a) => D (T a) -> a g' = undefined class G a where g :: D (T a) -> a g = g' instance G Char class H a where h :: T a -> a main = ((g (f (2 :: Int))) :: Char) `seq` return () {-# RULES "myrule" forall (x :: H a => T a). g' (f x) = h @a x #-}

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possible bug in latest hackage Elf (Elf-0.27)
by Baojun Wang 18 Feb '17

18 Feb '17

Hi list, with below test program: -- /* test1.c: build with -g -O0 */ include <stdio.h> static const char appmsg[] = "hello, world"; int main(int argc, char* argv[]) { fputs(appmsg, stdout); return 0; } --- elf-test1.hs module Main where import qualified Data.ByteString as B import qualified Data.ByteString.Char8 as C import Control.Monad import Data.Elf testelf = "/tmp/test1" testelfsym = C.pack "appmsg" lookupSymbol1 _ [] = Nothing lookupSymbol1 sym (t:ts) = case (snd (steName t)) of Nothing -> lookupSymbol1 sym ts Just sname -> if sname == sym then Just t else lookupSymbol1 sym ts lookupSymbol _ [] = Nothing lookupSymbol sym (t:ts) = case (lookupSymbol1 sym t) of Nothing -> lookupSymbol sym ts t1 -> t1 test1 elf symtab symbol = mapM_ (print) (elfSections elf) test2 elf symtab symbol = lookupSymbol symbol symtab test3 elf symtab symbol = lookupSymbol symbol symtab >>= \et -> findSymbolDefinition et mainloop elf symtab symbol = -- (test1 elf symtab symbol) >> print (test2 elf symtab symbol) >> print (test3 elf symtab symbol) >> return () main = do contents <- B.readFile testelf let elf = parseElf contents symtab = parseSymbolTables elf mainloop elf symtab testelfsym --- the latest Data.Elf doesn't geive correct output as expected: output will be: Just (EST {steName = (9,Just "appmsg"), steEnclosingSection = Just (ElfSection {elfSectionName = ".fini", elfSectionType = SHT_PROGBITS, elfSectionFlags = [SHF_EXECINSTR,SHF_ALLOC], elfSectionAddr = 4195908, elfSectionSize = 9, elfSectionLink = 0, elfSectionInfo = 0, elfSectionAddrAlign = 4, elfSectionEntSize = 0, elfSectionData = "H\131\236\bH\131\196\b\195"}), steType = STTObject, steBind = STBLocal, steOther = 0, steIndex = SHNIndex 14, steValue = 4195924, steSize = 13}) >From above, you can see the steEnclosingSection is wrong and offset by 1. The *correct* output should be: Just (EST {steName = (9,Just "appmsg"), steEnclosingSection = Just (ElfSection {elfSectionName = ".rodata", elfSectionType = SHT_PROGBITS, elfSectionFlags = [SHF_ALLOC], elfSectionAddr = 4195920, elfSectionSize = 17, elfSectionLink = 0, elfSectionInfo = 0, elfSectionAddrAlign = 4, elfSectionEntSize = 0, elfSectionData = "\SOH\NUL\STX\NULhello, world\NUL"}), steType = STTObject, steBind = STBLocal, steOther = 0, steIndex = SHNIndex 14, steValue = 4195924, steSize = 13}) Just "hello, world\NUL" After check Elf.hs, I found there could be two issues: 1) in sectionByIndex, (SHNIndex) should start from 0, not 1; this cause the steEnclosingSection from my exmaple offset by 1; 2) in findSymbolDefinition, start should substract the sectionAddr (base address). please see below diff for details: -- --- a/Elf.hs 2012-12-04 19:27:51.000000000 -0800 +++ b/Elf.hs 2014-05-14 22:57:01.014498515 -0700 @@ -1,5 +1,5 @@ -- | Data.Elf is a module for parsing a ByteString of an ELF file into an Elf record. -module Data.Elf ( parseElf +module Elf ( parseElf , parseSymbolTables , findSymbolDefinition , Elf(..) @@ -666,12 +666,12 @@ getSymbolTableEntries e s = -- If the size is zero, or the offset larger than the 'elfSectionData', -- then 'Nothing' is returned. findSymbolDefinition :: ElfSymbolTableEntry -> Maybe B.ByteString -findSymbolDefinition e = - let enclosingData = fmap elfSectionData (steEnclosingSection e) - start = fromIntegral (steValue e) +findSymbolDefinition e = steEnclosingSection e >>= \enclosingSection -> + let enclosingData = elfSectionData enclosingSection + start = ( (fromIntegral (steValue e)) - (fromIntegral (elfSectionAddr enclosingSection) ) ) len = fromIntegral (steSize e) - def = fmap (B.take len . B.drop start) enclosingData - in if def == Just B.empty then Nothing else def + def = (B.take len . B.drop start) enclosingData + in if def == B.empty then Nothing else Just def runGetMany :: Get a -> L.ByteString -> [a] runGetMany g bs @@ -712,7 +712,7 @@ getSymbolTableEntry e strtlb = return $ EST (nameIdx,name) sec typ bind other sTlbIdx symVal size sectionByIndex :: Elf -> ElfSectionIndex -> Maybe ElfSection -sectionByIndex e (SHNIndex i) = lookup i . zip [1..] $ (elfSections e) +sectionByIndex e (SHNIndex i) = lookup i . zip [0..] $ (elfSections e) sectionByIndex _ _ = Nothing infoToTypeAndBind :: Word8 -> (ElfSymbolType,ElfSymbolBinding) -- Would you please check above change and update Data.Elf hackage? I cannot find the author from http://hackage.haskell.org/package/elf-0.27 Thanks baojun

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[ANN] pi-lcd-0.1.0.0
by Patrick Pelletier 18 Feb '17

18 Feb '17

https://hackage.haskell.org/package/pi-lcd https://github.com/ppelleti/pi-lcd I recently bought an Adafruit LCD+Keypad Kit for Raspberry Pi. The LCD+Keypad Kit has a 16x2 character LCD, an RGB LED backlight (depending on the model), and five buttons. It works on all models of Raspberry Pi, and plugs into the GPIO header. https://www.adafruit.com/categories/808 Adafruit only supplies a Python library for communicating with the LCD+Keypad Kit. I wanted to program it in Haskell, so I wrote this Haskell library for communicating with it. The library automatically handles Unicode, using the LCD controller's built-in characters where possible, and using the "custom characters" feature, along with a 5x8 font bundled with this package, to emulate Unicode characters which are not built-in. The user of the library can also define their own custom characters. Everything you need to use one of these LCDs is exposed in the System.Hardware.PiLcd module. The submodules are only exposed because they might be useful to reuse for other types of hardware, such as if you are using an MCP23017 port expander or an HD44780 display controller in some other context. But if you're using the Adafruit LCD+Keypad Kit, all you need is System.Hardware.PiLcd. Before using this package, you'll need to make sure that I²C is enabled on your Raspberry Pi, under "Advanced Options" in raspi-config. Using PiLcd is as easy as: {-# LANGUAGE OverloadedStrings #-} import System.Hardware.PiLcd main = do lcd <- openPiLcd defaultLcdAddress defaultLcdOptions updateDisplay lcd ["Hello,", "World!"] setBacklightColor lcd Cyan closePiLcd lcd There are additional examples in the "examples" directory. This library is specifically designed to work with GHC 7.6.3 and up, and to not use Template Haskell, so it will work with the system-supplied version of GHC on Raspbian "Jessie." Just do "sudo apt-get install ghc cabal-install" and you're good to go. (You should also increase the swap space by editing /etc/dphys-swapfile.) There are other ways to install more recent versions of GHC if you want; see the "Raspberry Pi" page on the Haskell Wiki for details. This is a fairly early release, and there might be breaking changes in the future. Please contact me, by filing a GitHub issue, or by email, if you have any feedback on the library. I'm considering adding support for other LCDs, such as the Display-O-Tron 3000 and/or Display-O-Tron HAT. Let me know if you'd like to see support for those displays. I'd also be curious to hear how the library is being used!

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RFC 822 date parser
by David Turner 17 Feb '17

17 Feb '17

Hi all, Does anyone know of a more up-to-date parser for RFC822-formatted dates than the one I can find in the `time-http` package? That package hasn't been touched in a while and its dependencies seem rather dated. Many thanks, David

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VSTTE 2017 - First Call for Papers
by Andrei Paskevich 17 Feb '17

17 Feb '17

9th Working Conference on Verified Software: Theories, Tools, and Experiments (VSTTE) https://vstte17.lri.fr July 22-23, 2017, Heidelberg, Germany Co-located with the 29th International Conference on Computer-Aided Verification, CAV 2017 Important Dates * Abstract submission: Mon, Apr 24, 2017 * Full paper submission: Mon, May 1, 2017 * Notification: Mon, Jun 5, 2017 * VSTTE: Sat-Sun, Jul 22-23, 2017 * Camera-ready: Mon, Aug 21, 2017 Overview The goal of the VSTTE conference series is to advance the state of the art in the science and technology of software verification, through the interaction of theory development, tool evolution, and experimental validation. We welcome submissions describing significant advances in the production of verified software, i.e., software that has been proved to meet its functional specifications. Submissions of theoretical, practical, and experimental contributions are equally encouraged, including those that focus on specific problems or problem domains. We are especially interested in submissions describing large-scale verification efforts that involve collaboration, theory unification, tool integration, and formalized domain knowledge. We also welcome papers describing novel experiments and case studies evaluating verification techniques and technologies. Topics of interest for VSTTE include education, requirements modeling, specification languages, specification/verification/certification case studies, formal calculi, software design methods, automatic code generation, refinement methodologies, compositional analysis, verification tools (e.g., static analysis, dynamic analysis, model checking, theorem proving, satisfiability), tool integration, benchmarks, challenge problems, and integrated verification environments. Paper Submissions We accept both long (limited to 16 pages) and short (limited to 10 pages) paper submissions. Short submissions also cover Verification Pearls describing an elegant proof or proof technique. Submitted research papers and system descriptions must be original and not submitted for publication elsewhere. Each submission will be evaluated by at least three members of the Program Committee. We expect that one author of every accepted paper will present their work at the conference. Paper submissions must be written in English using the LNCS LaTeX format (http://www.springer.com/gp/computer-science/lncs/conference-proceedings-gui…) and must include a cogent and self-contained description of the ideas, methods, results, and comparison to existing work. Papers will be submitted via EasyChair at the VSTTE 2017 conference page (https://www.easychair.org/conferences/?conf=vstte2017) The post-conference proceedings of VSTTE 2017 will be published in the LNCS series. Authors of accepted papers will be requested to sign the copyright transfer form. A selection of best papers will be invited for publication in the Journal of Automated Reasoning. Program Committee * June Andronick (University of New South Wales, Australia) * Christel Baier (TU Dresden, Germany) * Sandrine Blazy (Université de Rennes 1, France) * Arthur Charguéraud (Inria, France) * Ernie Cohen (Amazon Web Services, USA) * Rayna Dimitrova (MPI-SWS, Germany) * Carlo A. Furia (Chalmers University of Technology, Sweden) * Arie Gurfinkel (University of Waterloo, Canada) * Hossein Hojjat (Rochester Institute of Technology, USA) * Marieke Huisman (University of Twente, Netherlands) * Bart Jacobs (KU Leuven, Belgium) * Rajeev Joshi (NASA Jet Propulsion Laboratory, USA) * Zachary Kincaid (Princeton University, USA) * Akash Lal (Microsoft Research, India) * Shuvendu Lahiri (Microsoft Research, USA) * Francesco Logozzo (Facebook, USA) * Peter Müller (ETH Zürich, Switzerland) * Jorge A. Navas (SRI International, USA) * Scott Owens (University of Kent, UK) * Andrei Paskevich (Université Paris-Sud, France), co-chair * Gerhard Schellhorn (Universität Augsburg, Germany) * Peter Schrammel (University of Sussex, UK) * Natarajan Shankar (SRI International, USA) * Mihaela Sighireanu (Université Paris-Diderot, France) * Julien Signoles (CEA LIST, France) * Michael Tautschnig (Queen Mary University of London, UK) * Tachio Terauchi (JAIST, Japan) * Oksana Tkachuk (NASA Ames Research Center, USA) * Mattias Ulbrich (Karlsruhe Institute of Technology, Germany) * Thomas Wies (New York University, USA), co-chair

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How to code Haskell in KDevelop in Windows
by vinod kc 16 Feb '17

16 Feb '17

Hi, I am new in Haskell. I installed GHC and KDevelop. But i don't know how to setup Haskell in KDevelop. Can anybody help me ? Thanks in advance -Vinod

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Self updating binary
by Pieter Laeremans 16 Feb '17

16 Feb '17

Hi there, Has anyone experience suggestions with writing self updating binaries for windows ? I have a small utility that I have to install on two "unmanaged" pc's, I would like to let the program check an url, for new versions, download a new versions, some how check that the program is valid (with a build in key, or certificate) and replace itself when necessary. Has anyone already done this in Haskell? Any suggestions, links ? Thanks, Pieter -- Pieter Laeremans pieter(a)laeremans.org

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Final Call for Papers: ICFP 2017
by Lindsey Kuper 16 Feb '17

16 Feb '17

ICFP 2017 The 22nd ACM SIGPLAN International Conference on Functional Programming Oxford, United Kingdom http://icfp17.sigplan.org/ Final Call for Papers ### Important dates Submissions due: Monday, February 27, Anywhere on Earth https://icfp17.hotcrp.com Author response: Monday, April 17, 2017, 15:00 (UTC) - Thursday, April 20, 2017, 15:00 (UTC) Notification: Monday, 1 May, 2017 Final copy due: Monday, 5 June 2017 Early registration: TBA Conference: Monday, 4 September - Wednesday, 6 September, 2017 ### New this year Those familiar with previous ICFP conferences should be aware of two significant changes that are being introduced in 2017: 1. Papers selected for ICFP 2017 will be published as the ICFP 2017 issue of a new journal, Proceedings of the ACM on Programming Languages (PACMPL), which replaces the previous ICFP conference proceedings. The move to PACMPL will have two noticeable impacts on authors: * A new, two-phase selection and reviewing process that conforms to ACM’s journal reviewing guidelines. * A new, single-column format for submissions. 2. Authors of papers that are conditionally accepted in the first phase of the reviewing process will have the option to submit materials for Artifact Evaluation. Further details on each of these changes are included in the following text. ### Scope ICFP 2017 seeks original papers on the art and science of functional programming. Submissions are invited on all topics from principles to practice, from foundations to features, and from abstraction to application. The scope includes all languages that encourage functional programming, including both purely applicative and imperative languages, as well as languages with objects, concurrency, or parallelism. Topics of interest include (but are not limited to): * *Language Design*: concurrency, parallelism, and distribution; modules; components and composition; metaprogramming; type systems; interoperability; domain-specific languages; and relations to imperative, object-oriented, or logic programming. * *Implementation*: abstract machines; virtual machines; interpretation; compilation; compile-time and run-time optimization; garbage collection and memory management; multi-threading; exploiting parallel hardware; interfaces to foreign functions, services, components, or low-level machine resources. * *Software-Development Techniques*: algorithms and data structures; design patterns; specification; verification; validation; proof assistants; debugging; testing; tracing; profiling. * *Foundations*: formal semantics; lambda calculus; rewriting; type theory; monads; continuations; control; state; effects; program verification; dependent types. * *Analysis and Transformation*: control-flow; data-flow; abstract interpretation; partial evaluation; program calculation. * *Applications*: symbolic computing; formal-methods tools; artificial intelligence; systems programming; distributed-systems and web programming; hardware design; databases; XML processing; scientific and numerical computing; graphical user interfaces; multimedia and 3D graphics programming; scripting; system administration; security. * *Education*: teaching introductory programming; parallel programming; mathematical proof; algebra. Submissions will be evaluated according to their relevance, correctness, significance, originality, and clarity. Each submission should explain its contributions in both general and technical terms, clearly identifying what has been accomplished, explaining why it is significant, and comparing it with previous work. The technical content should be accessible to a broad audience. ICFP 2017 also welcomes submissions in two separate categories --- Functional Pearls and Experience Reports --- that must be marked as such at the time of submission and that need not report original research results. Detailed guidelines on both categories are given at the end of this call. Please contact the program chair if you have questions or are concerned about the appropriateness of a topic. ### Preparation of submissions ICFP 2017 will employ a lightweight double-blind reviewing process, as described below. **Deadline**: The deadline for submissions is Monday, February 27, 2017, Anywhere on Earth (<https://en.wikipedia.org/wiki/Anywhere_on_Earth>). This deadline will be strictly enforced. **Formatting**: (NOTE: NEW FORMAT REQUIREMENTS FOR ICFP 2017) Submissions must be in PDF format, printable in black and white on US Letter sized paper, and interpretable by common PDF tools. All submissions must adhere to the "ACM Large" template that is available (in both LaTeX and Word formats) from <http://www.acm.org/publications/proceedings-template>. For authors using LaTeX, a lighter-weight package, including only the essential files, is available from <http://sigplan.org/Resources/Author/#acmart-format>; the appropriate template for ICFP 2017 authors is in the file `acmart-pacmpl-template.tex`. As documented in the template, submissions should be prepared using the `acmlarge` and `anonymous` options. The use of the `review` option is also strongly encouraged but not required. (The `review` option will add line numbers, which will make it easier for reviewers to reference specific parts of your paper in their comments, but should have absolutely no other effect on the typesetting.) Details of available technical support for LaTeX-specific questions is available at <http://www.acm.org/publications/proceedings-template#h-technical-support>. There is a limit of 24 pages for a full paper or 12 pages for an Experience Report; in either case, the bibliography will not be counted against these limits. These page limits have been chosen to allow essentially the same amount of content with the new single-column format as was possible with the two-column format used in past ICFP conferences. Submissions that exceed the page limits or, for other reasons, do not meet the requirements for formatting, will be summarily rejected. **Citations**: As part of PACMPL, ICFP 2017 papers are expected to use author-year citations for references to other work. Author-year citations may be used as either a noun phrase, such as "The lambda calculus was originally conceived by Church (1932)", or a parenthetic phrase, such as "The lambda calculus (Church 1932) was intended as a foundation for mathematics". A useful test for correct usage it to make sure that the text still reads correctly when the parenthesized portions of any references are omitted. Take care with prepositions; in the first example above, "by" is more appropriate than "in" because it allows the text to be read correctly as a reference to the author. Sometimes, readability may be improved by putting parenthetic citations at the end of a clause or a sentence, such as "A foundation for mathematics was provided by the lambda calculus (Church 1932)". In LaTeX, use `\citet{Church-1932}` for citations as a noun phrase, "Church (1932)", and `\citep{Church-1932}` for citations as a parenthetic phrase, "(Church 1932)"; for details, see Sections 2.3--2.5 of the natbib documentation (<http://ctan.org/pkg/natbib>). **Submission**: Submissions will be accepted at <https://icfp17.hotcrp.com/>. Improved versions of a paper may be submitted at any point before the submission deadline using the same web interface. **Author Response Period**: Authors will have a 72-hour period, starting at 15:00 UTC on Monday, April 17, 2017, to read reviews and respond to them. **Supplementary Materials**: Authors have the option to attach supplementary material to a submission, on the understanding that reviewers may choose not to look at it. The material should be uploaded at submission time, as a single pdf or a tarball, not via a URL. This supplementary material may or may not be anonymized; if not anonymized, it will only be revealed to reviewers after they have submitted their review of the paper and learned the identity of the author(s). **Authorship Policies**: All submissions are expected to comply with the ACM Policies for Authorship that are detailed at <https://www.acm.org/publications/authors/information-for-authors>. **Republication Policies**: Each submission must adhere to SIGPLAN's republication policy, as explained on the web at <http://www.sigplan.org/Resources/Policies/Republication>. **Resubmitted Papers**: Authors who submit a revised version of a paper that has previously been rejected by another conference have the option to attach an annotated copy of the reviews of their previous submission(s), explaining how they have addressed these previous reviews in the present submission. If a reviewer identifies him/herself as a reviewer of this previous submission and wishes to see how his/her comments have been addressed, the program chair will communicate to this reviewer the annotated copy of his/her previous review. Otherwise, no reviewer will read the annotated copies of the previous reviews. ### Review Process This section outlines the two-stage process with lightweight double-blind reviewing that will be used to select papers for presentation at ICFP 2017. A [list of frequently asked questions and answers](http://icfp17.sigplan.org/track/icfp-2017-papers#Submission-and-Re… that address common concerns is available on the conference website and will be updated as necessary to clarify and expand on this process. **ICFP 2017 will employ a two-stage review process.** The first stage in the review process will assess submitted papers using the criteria stated above and will allow for feedback and input on initial reviews through the author response period mentioned previously. At the PC meeting, a set of papers will be conditionally accepted and all other papers will be rejected. Authors will be notified of these decisions on May 1, 2017. Authors of conditionally accepted papers will be provided with committee reviews (just as in previous conferences) along with a set of mandatory revisions. After five weeks (June 5, 2017), the authors will provide a second submission. The second and final reviewing phase assesses whether the mandatory revisions have been adequately addressed by the authors and thereby determines the final accept/reject status of the paper. The intent and expectation is that the mandatory revisions can be addressed within five weeks and hence that conditionally accepted papers will in general be accepted in the second phase. The second submission should clearly identify how the mandatory revisions were addressed. To that end, the second submission must be accompanied by a cover letter mapping each mandatory revision request to specific parts of the paper. The cover letter will facilitate a quick second review, allowing for confirmation of final acceptance within two weeks. Conversely, the absence of a cover letter will be grounds for the paper’s rejection. This process is intended as a refinement of the review process that has been used in previous ICFP conferences. By incorporating a second stage, the process will conform to ACM’s journal reviewing guidelines for PACMPL. **ICFP 2017 will employ a lightweight double-blind reviewing process.** To facilitate this, submitted papers must adhere to two rules: 1. **author names and institutions must be omitted**, and 2. **references to authors' own related work should be in the third person** (e.g., not "We build on our previous work ..." but rather "We build on the work of ..."). The purpose of this process is to help the PC and external reviewers come to an initial judgement about the paper without bias, not to make it impossible for them to discover the authors if they were to try. Nothing should be done in the name of anonymity that weakens the submission or makes the job of reviewing the paper more difficult (e.g., important background references should not be omitted or anonymized). In addition, authors should feel free to disseminate their ideas or draft versions of their paper as they normally would. For instance, authors may post drafts of their papers on the web or give talks on their research ideas. ### Information for Authors of Accepted Papers * As a condition of acceptance, final versions of all papers must adhere to the new ACM Large format. The page limits for final versions of papers will be increased to ensure that authors have space to respond to reviewer comments and mandatory revisions. * Authors of accepted submissions will be required to agree to one of the three ACM licensing options: copyright transfer to ACM; retaining copyright but granting ACM exclusive publication rights; or open access on payment of a fee. Further information about ACM author rights is available from <http://authors.acm.org>. * At least one author of each accepted submission will be expected to attend and present their paper at the conference. (ICFP welcomes all authors, regardless of nationality. If any author of an accepted submission has visa-related difficulties in travelling to the conference, we will make arrangements to enable remote participation, and not require them to attend the conference in order to present their talk. In such a case contact us (icfp2017(a)cs.ox.ac.uk) for further guidance.) The schedule for presentations will be determined and shared with authors after the full program has been selected. Presentations will be videotaped and released online if the presenter consents. * We intend that the proceedings will be freely available for download from the ACM Digital Library in perpetuity via the OpenTOC mechanism. * ACM Author-Izer is a unique service that enables ACM authors to generate and post links on either their home page or institutional repository for visitors to download the definitive version of their articles from the ACM Digital Library at no charge. Downloads through Author-Izer links are captured in official ACM statistics, improving the accuracy of usage and impact measurements. Consistently linking to the definitive version of an ACM article should reduce user confusion over article versioning. After an article has been published and assigned to the appropriate ACM Author Profile pages, authors should visit <http://www.acm.org/publications/acm-author-izer-service> to learn how to create links for free downloads from the ACM DL. * **AUTHORS TAKE NOTE: The official publication date is the date the proceedings are made available in the ACM Digital Library. This date may be up to *two weeks prior* to the first day of the conference. The official publication date affects the deadline for any patent filings related to published work.** ### Artifact Evaluation Authors of papers that are conditionally accepted in the first phase of the review process will be encouraged (but not required) to submit supporting materials for Artifact Evaluation. These items will then be reviewed by a committee, separate from the program committee, whose task is to assess how the artifacts support the work described in the associated paper. Papers that go through the Artifact Evaluation process successfully will receive a seal of approval printed on the papers themselves. Authors of accepted papers will be encouraged to make the supporting materials publicly available upon publication of the proceedings, for example, by including them as "source materials" in the ACM Digital Library. An additional seal will mark papers whose artifacts are made available, as outlined in the ACM guidelines for artifact badging. Participation in Artifact Evaluation is voluntary and will not influence the final decision regarding paper acceptance. Further information about the motivations and expectations for Artifact Evaluation can be found at <http://icfp17.sigplan.org/track/icfp-2017-Artifacts>. ### Special categories of papers In addition to research papers, ICFP solicits two kinds of papers that do not require original research contributions: Functional Pearls, which are full papers, and Experience Reports, which are limited to half the length of a full paper. Authors submitting such papers should consider the following guidelines. #### Functional Pearls A Functional Pearl is an elegant essay about something related to functional programming. Examples include, but are not limited to: * a new and thought-provoking way of looking at an old idea * an instructive example of program calculation or proof * a nifty presentation of an old or new data structure * an interesting application of functional programming techniques * a novel use or exposition of functional programming in the classroom While pearls often demonstrate an idea through the development of a short program, there is no requirement or expectation that they do so. Thus, they encompass the notions of theoretical and educational pearls. Functional Pearls are valued as highly and judged as rigorously as ordinary papers, but using somewhat different criteria. In particular, a pearl is not required to report original research, but, it should be concise, instructive, and entertaining. A pearl is likely to be rejected if its readers get bored, if the material gets too complicated, if too much specialized knowledge is needed, or if the writing is inelegant. The key to writing a good pearl is polishing. A submission that is intended to be treated as a pearl must be marked as such on the submission web page, and should contain the words "Functional Pearl" somewhere in its title or subtitle. These steps will alert reviewers to use the appropriate evaluation criteria. Pearls will be combined with ordinary papers, however, for the purpose of computing the conference's acceptance rate. #### Experience Reports The purpose of an Experience Report is to help create a body of published, refereed, citable evidence that functional programming really works --- or to describe what obstacles prevent it from working. Possible topics for an Experience Report include, but are not limited to: * insights gained from real-world projects using functional programming * comparison of functional programming with conventional programming in the context of an industrial project or a university curriculum * project-management, business, or legal issues encountered when using functional programming in a real-world project * curricular issues encountered when using functional programming in education * real-world constraints that created special challenges for an implementation of a functional language or for functional programming in general An Experience Report is distinguished from a normal ICFP paper by its title, by its length, and by the criteria used to evaluate it. * Both in the proceedings and in any citations, the title of each accepted Experience Report must begin with the words "Experience Report" followed by a colon. The acceptance rate for Experience Reports will be computed and reported separately from the rate for ordinary papers. * Experience Report submissions can be at most 12 pages long, excluding bibliography. * Each accepted Experience Report will be presented at the conference, but depending on the number of Experience Reports and regular papers accepted, authors of Experience reports may be asked to give shorter talks. * Because the purpose of Experience Reports is to enable our community to accumulate a body of evidence about the efficacy of functional programming, an acceptable Experience Report need not add to the body of knowledge of the functional-programming community by presenting novel results or conclusions. It is sufficient if the Report states a clear thesis and provides supporting evidence. The thesis must be relevant to ICFP, but it need not be novel. The program committee will accept or reject Experience Reports based on whether they judge the evidence to be convincing. Anecdotal evidence will be acceptable provided it is well argued and the author explains what efforts were made to gather as much evidence as possible. Typically, more convincing evidence is obtained from papers which show how functional programming was used than from papers which only say that functional programming was used. The most convincing evidence often includes comparisons of situations before and after the introduction or discontinuation of functional programming. Evidence drawn from a single person's experience may be sufficient, but more weight will be given to evidence drawn from the experience of groups of people. An Experience Report should be short and to the point: it should make a claim about how well functional programming worked on a particular project and why, and produce evidence to substantiate this claim. If functional programming worked in this case in the same ways it has worked for others, the paper need only summarize the results --- the main part of the paper should discuss how well it worked and in what context. Most readers will not want to know all the details of the project and its implementation, but the paper should characterize the project and its context well enough so that readers can judge to what degree this experience is relevant to their own projects. The paper should take care to highlight any unusual aspects of the project. Specifics about the project are more valuable than generalities about functional programming; for example, it is more valuable to say that the team delivered its software a month ahead of schedule than it is to say that functional programming made the team more productive. If the paper not only describes experience but also presents new technical results, or if the experience refutes cherished beliefs of the functional-programming community, it may be better off submitted it as a full paper, which will be judged by the usual criteria of novelty, originality, and relevance. The program chair will be happy to advise on any concerns about which category to submit to. ### Organizers General Chair: Jeremy Gibbons (University of Oxford, UK) Program Chair: Mark Jones (Portland State University, USA) Artifact Evaluation Chair: Ryan R. Newton (Indiana University, USA) Industrial Relations Chair: Ryan Trinkle (Obsidian Systems LLC, USA) Programming Contest Organiser: Sam Lindley (University of Edinburgh, UK) Publicity and Web Chair: Lindsey Kuper (Intel Labs, USA) Student Research Competition Chair: Ilya Sergey (University College London, UK) Video Chair: Jose Calderon (Galois, Inc., USA) Workshops Co-Chair: Andres Löh (Well-Typed LLP) Workshops Co-Chair: David Christiansen (Indiana University, USA) Program Committee: Bob Atkey (University of Strathclyde, Scotland) Adam Chlipala (MIT, USA) Dominique Devriese (KU Leuven, Belgium) Martin Erwig (Oregon State, USA) Matthew Flatt (University of Utah, USA) Ronald Garcia (University of British Columbia, Canada) Kathryn Gray (University of Cambridge, England) John Hughes (Chalmers University and Quvik, Sweden) Chung-Kil Hur (Seoul National University, Korea) Graham Hutton (University of Nottingham, England) Alan Jeffrey (Mozilla Research, USA) Ranjit Jhala (University of California, San Diego, USA) Shin-ya Katsumata (Kyoto University, Japan) Lindsey Kuper (Intel Labs, USA) Dan Licata (Wesleyan University, USA) Ben Lippmeier (Digital Asset, Australia) Gabriel Scherer (Northeastern University, USA) Alexandra Silva (University College London, England) Nikhil Swamy (Microsoft Research, USA) Sam Tobin-Hochstadt (Indiana University, USA) Nicolas Wu (University of Bristol, England) Beta Ziliani (CONICET and FAMAF, Universidad Nacional de Córdoba, Argentina)

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Re: [Haskell-cafe] Extensible records & mandatory/optional record fields
by Anthony Clayden 16 Feb '17

16 Feb '17

> On 15 February 2017 at 23:06 Harendra Kumar wrote: >> On 16 February 2017 at 02:31, Anthony Clayden wrote: > > > I am aware of the ghc "overloaded records" proposal. rawr > provides anonymous extensible records using the overloaded > labels feature of ghc 8. Records can be merged or > partitioned. I believe, the key difference between > "overloaded records" and rawr is that the latter provides > extensible records while the former does not. Yes. But you seem to be talking about a different 'feature' of rawr. For gathering params to a function, I see no need for extensible records. The params are known at compile time. If for a DSL you want 'optional' fields, make them Maybe's, with a default of Nothing. > > I am trying to write a program which provides a friendly > high level DSL to the user. 'user' here seems to mean programmer, if you're looking for static guarantees. > I want a pure function like > API but instead of passing positional parameters I want > the user to be able to specify arguments based on keywords > and be able to skip any optional arguments. Something like > the following, name is mandatory and email is optional: > > maintainer (#name := "Harendra Kumar", #email := > "xyz(a)gmail.com") > > I can achieve this using rawr. The argument to the > function is an anonymous record ... OK. But I'm not seeing why it has to be anonymous. Again, if it's for a specific function, it needs specific parameters. An anonymous record might provide keywords not valid, as well as fail to provide keywords expected. > and we can pattern match > partially using the mandatory fields in the record to > statically check that those fields are present. OK. That's the critical feature you want, then. It wasn't clear from your O.P. > > I was only trying to say that this is a pretty > useful feature in python and I guess in some other > imperative languages too. (I don't think it's anything to do with programming paradigm.) > It allows you to write self > documenting code where necessary. No the code you posted was not self-documenting. (The comments were useful, thank you.) Only a python-charmer would claim code full of graphic chars is 'self-documenting'. I have no idea what it was that made #name mandatory but #email not. > It will be nice if we have a way to achieve something like this. > There's nothing in the standard language currently. > > [example] > This is the first approach that I tried, this is commonly > used in many libraries. The only drawback with this is > that I cannot enforce mandatory/optional fields > statically. All fields are optional in this case. So your DSL is going to be compiled? Not intepreted? Including putting in values like #name? I'd expect #name would come from end-user input at run time(?) Yes the approach I illustrated is common in many libraries. Perhaps authors of those libraries are listening in, and could comment. AntC

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Re: [Haskell-cafe] Extensible records & mandatory/optional record fields
by Anthony Clayden 15 Feb '17

15 Feb '17

> On Tue, 14 Feb 2017 at 18:50, Harendra Kumar said: > In my application, I want some of the fields in a record to have default > values while others must always be specified by the user. I can implement > this using the rawr records library (http://hackage.haskell.org/package/rawr) Hi Harendra. I believe rawr builds on some of the work in 'overloaded records'. That's a suite of features being developed right now look here for what's coming soon https://github.com/adamgundry/ghc-proposals/blob/overloaded-record-fields/p… > like so: > > def :: ("b" := String) -> R ("a" := Int, "b" := String) > def t = (R (#a := 0) :*: R t) -- merge with defaults > > let r = def (#b := "hello") That looks like some sort of anonymous/extensible records system. What is data constructor `R`; where is it defined? There's a few mentions of 'anonymous' records on that link above. (And mention of rawr.) It's not clear what you're trying to do. Do you need anonymous/extensible records? Why use `let` to bind a value for `r`? > Here field "a" has a default value (i.e. it is optional when "def" is used) > but field "b" does not have a default value and has to be explicitly > specified by the user. This is made possible by record merging feature of > rawr, making the record extensible. > I could not find an equivalent way of achieving this using overloaded > records (http://hackage.haskell.org/package/overloaded-records) So far, overloaded records is based on standard-ish Haskell record decls. So you must declare a distinct record constructor and field labels. Like data MyR = MyR { a :: Int, b :: String }; If you want default values: myRdef = MyR{ a = 0 }; -- don't have to give b Then bind some value, to incorp defaults. r = myRdef { b = "hello" }; -- takes the defult for a > Is record merging possible or can be made possible It looks to me like you don't need '"record merging". What do you think it is; why do you think you need it? > using overloaded-records or with the ghc overloaded records poposal? > If not, is there a plan to make something like this possible in future? I'd say it's on the radar, but a long way off. > Or will this never be possible with the in built record syntax? I think that built-in record syntax will fit your requirements. > Note that, this is handy to simulate mandatory and optional keyword > arguments to a function by passing them in the form of a record. Sure. Keyword arguments to a function are fixed. No need for building dynamic/anonymous structures. Yes it's good (and standard practice) to pass as a record. So you can use a standard built-in Haskell record decl, as I used above. > Something which is available in other languages like python. It looks to me that you're trying to write Python code in Haskell. Not a good idea. Use built-in/static features first. Think about the difference between a compiled vs interpreted language. Only when static features really really aren't working, consider dynamic/extensible. AntC

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Applicative transformers
by Laurent Christophe 15 Feb '17

15 Feb '17

Hi guys, the way `StateT` are implemented as `Applicative` have been buggling my mind for some time. https://hackage.haskell.org/package/transformers-0.5.2.0/docs/src/Control.M… <https://hackage.haskell.org/package/transformers-0.5.2.0/docs/src/Control.M…> instance (Functor m, Monad m) => Applicative (StateT s m) where pure a = StateT $ \ s -> return (a, s) StateT mf <*> StateT mx = StateT $ \ s -> do (f, s') <- mf s (x, s'') <- mx s' return (f x, s'') Using dependant monadic computations, this implementation cannot be expressed in term of applicative. This explains why we cannot have `instance (Applicative m) => Applicative (State s m)`. However using real monadic style computations for implementing `<*>` buggles my mind. Moreover `liftA2 (<*>)` can be used to generically compose applicative functors so why monads are needed? https://www.haskell.org/haskellwiki/Applicative_functor#Applicative_transfo… <https://www.haskell.org/haskellwiki/Applicative_functor#Applicative_transfo…> Any inputs would be greatly appreciated! Cheers, Laurent

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1st call for papers: Trends in Functional Programming, 19-21 june 2017, University of Kent, Canterbury
by Peter Achten 15 Feb '17

15 Feb '17

----------------------------- C A L L F O R P A P E R S ----------------------------- ======== TFP 2017 =========== 18th Symposium on Trends in Functional Programming 19-21 June, 2017 University of Kent, Canterbury https://www.cs.kent.ac.uk/events/tfp17/index.html 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 (see below). Authors of draft papers will be invited to submit revised papers based on the feedback receive at the symposium. A post-symposium refereeing process will then select a subset of these articles for formal publication. TFP 2017 will be the main event of a pair of functional programming events. TFP 2017 will be accompanied by the International Workshop on Trends in Functional Programming in Education (TFPIE), which will take place on 22 June. The TFP symposium is the heir of the successful series of Scottish Functional Programming Workshops. Previous TFP symposia were held in * Edinburgh (Scotland) in 2003; * Munich (Germany) in 2004; * Tallinn (Estonia) in 2005; * Nottingham (UK) in 2006; * New York (USA) in 2007; * Nijmegen (The Netherlands) in 2008; * Komarno (Slovakia) in 2009; * Oklahoma (USA) in 2010; * Madrid (Spain) in 2011; * St. Andrews (UK) in 2012; * Provo (Utah, USA) in 2013; * Soesterberg (The Netherlands) in 2014; * Inria Sophia-Antipolis (France) in 2015; * and Maryland (USA) in 2016. For further general information about TFP please see the TFP homepage. (http://www.tifp.org/) == 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 2017 program chairs, Scott Owens and Meng Wang. == 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. == SPONSORS == TBD == PAPER SUBMISSIONS == Acceptance of articles for presentation at the symposium is based on a lightweight peer review process of 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. We use EasyChair for the refereeing process. Papers must be submitted at: https://easychair.org/conferences/?conf=tfp17 Papers must be written in English, and written using the LNCS style. For more information about formatting please consult the Springer LNCS web site: http://www.springer.com/computer/lncs?SGWID=0-164-6-793341-0 == IMPORTANT DATES == Submission of draft papers: 5 May, 2017 Notification: 12 May, 2017 Registration: 11 June, 2017 TFP Symposium: 19-21 June, 2017 Student papers feedback: 29 June, 2017 Submission for formal review: 2 August, 2017 Notification of acceptance: 3 November, 2017 Camera ready paper: 2 December, 2017 == PROGRAM COMMITTEE == TBD

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Re: [Haskell-cafe] Lenses and records and ecosystem
by Anthony Clayden 14 Feb '17

14 Feb '17

> On Sat, Feb 11, 2017 at 21:04, David Menendez wrote: > > On Fri, Feb 10, 2017 at 7:53 PM, Anthony Clayden wrote: > > > > Certainly (.) for lenses works 'backwards' > > (i.e. suffix style) > > compared to function-prefix style. > > (As any Lens tutorial will say.) > > > > Those tutorials are oversimplifying. Thank you David, ho hum I'm not getting much feedback about ecosystem/ co-existence; nor a specialised composition operator. > Lenses (and their relatives) transform operations, not values. So it must be a stubborn superstition on my part that getting/putting from/to structures is about values. I'm not here to 'knock' lenses (of whichever model), but every time I scratch the surface, the answers wander off into category theory and higher-order types. I'll draw a comparison with another place in Haskell where category theory has huge benefits: monads. There's less than a handful of operators for monads, and those are conveniently handled behind some elegant syntactic sugar (do-notation). So a newbie doesn't really need to grok monads. They can get on and use them; learn the theory later. Can that be said of lenses? I guess part of the trouble is that H98 record operations have gobbled up so much of the syntactic design space. Nevertheless I don't see what syntactic sugar could help with lenses. > Composition of lenses is exactly like composition of functions, with > the inner-most operation on the right. That doesn't seem to say more than "it's composition". If I want to get a foo out of a bar out of a baz in a s, I'd (perhaps naievely) go foo (bar (baz s)) -- i.e. (foo . bar . baz) s And I'm using function application all the way through. I'd only think of doing s.baz.bar.foo If I was trying to mimic OO style methods. And anyway with lenses, that's exactly what I _can't_ do. Lenses do not use function application of the lens to the structure. You need an extra operator (view, over). Then I'm not seeing the syntactic merit of using composition (.) for lenses. It's certainly making the mental machinery incompatible for lenses vs records, even if they can co-exist semantically. > A lens foo :: Lens > O I transforms an operation on I into an operation on O. A > composition outer.inner turns an operation on the target > of inner into an operation on the source of outer. > > This is demonstrated by the way over distributes with (.): > > over (outer . inner) = over outer . over inner > > What confuses people is view, which is contravariant: > > view (outer . inner) = view inner . view outer > > but you can't avoid having one of over and view be > contravariant. OK. (Why did it need so much category theory to explain that?) And why do those nifty equivalences have to intrude so much into the surface syntax, just to get a value out of a structure? AntC

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Haskell.org committee financial statement 2016
by Gershom B 14 Feb '17

14 Feb '17

Dear Haskellers, The Haskell.org Committee [1] manages funds for haskell.org and oversees haskell.org infrastructure. The funds available to Haskell.org have historically come from two sources: 1) Mentor payments from the Google Summer of Code program. 2) Donations [2] from the Haskell community at large. Haskell.org is a registered 501(c)3 nonprofit. A portion of our funds are held by Software in the Public Interest, also a 501(c)3 US non-profit, through which we also accept donations. In 2016 we were not accepted into the GSoC program, and ran a summer of haskell program along similar lines, funded by earmarked donations provided by individual and corporate sponsors and from our pool of general funds. A full list of sponsors is on the soh webpage [3]. According to our charter, "Each year, the committee will post a statement of the haskell.org assets, and the transactions for that year." Included in this message is a brief statement of Haskell.org assets over the period 1 December 2015 - 31 December 2016. Aside from the SOH disbursements, our expenses are nearly entirely hosting, with a small overhead incurred by payment processing. SOH thus accounts for both our increased revenue (in the form of earmarked donations) and expenses this year. We do not have full statements from our SPI account yet, as their treasury reports are only complete through october at this time [4] although I hope that will be changed shortly. So this statement is produced as though the income and expenses on our spi account for the last for months of 2016 were net zero, though that was obviously not the case. Even in this incomplete state, I think it is better to provide this than nothing. Additionally, as this covers holdings in our haskell.org bank account, it does not reflect when funds received via paypal donations, are received by paypal, but rather when the lump sum transfers from them are received by us. So paypal donations made in December 2016, for example, will likely be reflected in our 2017 statement. A portion of the income in 2016 is also attributable to gsoc mentor payment from our participation in the 2015 program. Thanks to many generous donations, despite the substantial haskell summer of code expenditures, we are nonetheless net-positive in income (though the difference just about amounts to the outstanding gsoc payments from 2015). We hope to find good opportunity to put our reserves to use again in the coming year. 1. Income and Expenses Total revenue over 2016: 54,802.56 Total expenses over 2016: 48,344.05 ---- Net income over 2016: 6,458.51 2. Total Balance Balance as of 31 December 2015: 32,882.34 Balance as of 31 December 2016: 39,340.85 [1] https://wiki.haskell.org/Haskell.org_committee [2] https://wiki.haskell.org/Donate_to_Haskell.org [3] https://summer.haskell.org/ [5] http://spi-inc.org/treasurer/reports/ Best, Gershom for the Haskell.org Committee

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Loading JSON into a set of nested index-able structures
by Carl Petersen 14 Feb '17

14 Feb '17

Hello All, I've used Aeson to load a JSON object with nested lists into a set of data structures, but what I really need is to load it into a set of data structures that are index-able such as a HashMap. I've had success loading the JSON into a structure with the lowest level being a HashMap using !Object, but I'm having difficulty in figuring out how to nest the HashMaps. Any hints or direction would be appreciated. Thanks, Carl

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Extensible records & mandatory/optional record fields
by Harendra Kumar 14 Feb '17

14 Feb '17

In my application, I want some of the fields in a record to have default values while others must always be specified by the user. I can implement this using the rawr records library (http://hackage.haskell.org/package/rawr) like so: def :: ("b" := String) -> R ("a" := Int, "b" := String) def t = (R (#a := 0) :*: R t) -- merge with defaults let r = def (#b := "hello") Here field "a" has a default value (i.e. it is optional when "def" is used) but field "b" does not have a default value and has to be explicitly specified by the user. This is made possible by record merging feature of rawr, making the record extensible. I could not find an equivalent way of achieving this using overloaded records (http://hackage.haskell.org/package/overloaded-records) Is record merging possible or can be made possible using overloaded-records or with the ghc overloaded records poposal? If not, is there a plan to make something like this possible in future? Or will this never be possible with the in built record syntax? Note that, this is handy to simulate mandatory and optional keyword arguments to a function by passing them in the form of a record. Something which is available in other languages like python. -harendra

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Myrtle Software is hiring for Haskell positions in Hardware and Machine Learning!
by Joe Hermaszewski 14 Feb '17

14 Feb '17

Myrtle is looking for multiple skilled Haskell developers to join our growing development team writing a compiler for generating highly efficient hardware designs implementing machine learning solutions. We use Haskell for every aspect of our work and developers will get the chance to be involved in every part of the project. As an example, some things we’ve worked on recently are a tiny CPU to implement a custom network protocol to communicate between a PC and an FPGA and a Haskell implementation of part of the Caffe deep learning framework. Specific tasks you could be working on soon include: implementing fixed point neural network evaluation support in our compiler, supporting AWS F1 instances as a backend, investigating and implementing exciting techniques for neural network evaluation such as the Winograd small convolution algorithm and realising full hardware implementations of existing neural networks. A familiarity and interest with hardware design would be viewed positively but is not essential. Applicants should be familiar with Unix based systems; all our development is done on Ubuntu or NixOS. Applicants should send a resume and covering email, stating your suitability for this role, to jobs(a)myrtlesoftware.com. Please include any links to blog posts, repositories or any other media which demonstrates your skill set. Roles will be based at our offices in Cambridge, UK. Closing date for applications 5pm, 13th March 2017 About Myrtle Myrtle is a software company based in Cambridge UK with a long history of working at the forefront of compiler technology. We are best known for having helped produce computer generated images for over twenty major Hollywood movies including the Transformers franchise. Myrtle’s clients have included NYSE and NASDAQ listed companies in LA, Vancouver and London. -- Joe https://www.myrtlesoftware.com/vacancies/

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Re: [Haskell-cafe] Sublime2/3 hsdev patch: testers needed
by Ara Adkins 14 Feb '17

14 Feb '17

Looks like this has fixed an issue I've been having! Seems to have just been merged into master as of ~4 hours ago at the time of writing. Thanks Scott! - Ara > On 13 Feb 2017, at 06:40, Scott Michel <scooter.phd(a)gmail.com> wrote: > > Was wondering if there are any Sublime Text users out there who also use hsdev as their Haskell IDE backend. I'd recently (within the last 2 weeks) encountered random lockups, error messages about resources no longer available. I was able to track them down to half-closed pipes and ended up revamping subprocess interaction. So far, I have left a SublimeText session open for 3 days, done some fair amount of work and haven't had any problems. > > If you are a SublimeText 2/3 hsdev user and are comfortable with checking out Sublime packages directly from github, I could use some extra help shaking out the code to ensure that it is as robust as I think it is. The URL to my Github fork is: > > https://github.com/bscottm/SublimeHaskell.git > > Once you've cloned my fork, check out the 'stderr_stdout' branch and test away -- I'm looking for unexpected lockups (e.g., when you've saved a file and ST's status line says "... Checking and Linting" forever.) > > Thanks! > > > -scooter

2 1

A question about GHC test coverage
by ok＠cs.otago.ac.nz 13 Feb '17

13 Feb '17

Step 1: write a module defining a data type. Step 2: write a module with lots of QuickCheck tests for it. Step 3: Compile with gcc -fhpc to get coverage data. Step 4: run, find bugs, fix bugs, repeat from step 3. Step 5: view coverage .html files, note functions not covered, add tests to step 2 file, repeat. Step 6: Step back with a sigh of content. Coverage high. Step 7, some time later: encounter a bug in an untested function. Why? Because Step 1 includes instance Ord MyType where compare ... ... = ... and the untested function was max. The "inherited" definition is of course fully consistent with compare, and comparison had been tested because I thought of that, but there was an extra requirement which need not detain us here. My problem was that (a) I was too dumb to think of writing tests for a function I hadn't written. (b) Because I hadn't written max, 'hpc' didn't show it to me as something needing a test. Obviously this was my fault: if I have declared instance <some class> <my type> it's my responsibility to test all of the functions in the type-class. But I might not actually *know* what all the functions in the type-class are; Haskell does change from time to type. And being a bear of very little brain, I could use some reminders "Hey, you've inherited this function but not tested it". Is that possible using ghc -hpc?

1 0

Fully funded PhD position in CS at Heriot-Watt University, Edinburgh, Scotland
by Ekaterina Komendantskaya 13 Feb '17

13 Feb '17

Dependable System group, School of Mathematical and Computer Sciences, Heriot-Watt University, Edinburgh, is looking to fill in one PhD position (a PhD stipend of £14,300 per annum, for 48 months, and a fee waiver are offered, no nationality restrictions apply). We are looking for a talented person, with 1st class degree in Mathematics or Computer Science, with keen interest in Logic and Programming languages and good programming skills. The successful candidate will be working under supervision of Dr Ekaterina Komendantskaya (http://www.macs.hw.ac.uk/~ek19/) The exact topic of the PhD dissertation will be determined in the course of discussions with the successful candidate, and will be related to both the student’s and the supervisor's research interests. To apply please contact Ekaterina directly: ek19(a)hw.ac.uk Heriot-Watt University. With a history dating back to 1821, Heriot-Watt University is a research-led university located in Edinburgh, UK. Currently it is Scotland’s most international university, delivering degree programmes to 31,000 students globally and with campuses in Edinburgh, Scottish Borders, Orkney, Dubai and Malaysia. The university is consistently highly ranked, having been The Sunday Times; Scottish University of Year between 2011 and 2013. The university has a strong track record in attracting funding for research from national Research Councils, UK government departments, charities, the European Commission and industrial sponsors. In the REF 2014 survey of all UK universities, 82% of our research was found to be world-class. Dependable Systems group. The Computer Science department, hosting this PhD position, had 78% of its outputs rated `world-leading' or `internationally excellent' in REF 2014.The proposed work will be carried out within the Dependable Systems Group (DSG). With members of staff working on programming languages and compilers (Fensch, Loidl, Michaelson, Scholz), Automated Reasoning and Formal Methods (Georgieva, Grov, Ireland, Komendantskaya), Type Theory (Gabbay), this group will provide an ideal environment for the PhD research. Additionally, the DSG is an active member of the multi-site Mathematical Reasoning Group (joint with U. Edinburgh); the sites holding weekly research meetings and a joint platform grant. ******************************* Dr Ekaterina Komendantskaya Associate Professor in Computer Science School of Mathematical and Computer Sciences Earl Mountbatten Building [ building 21, office G26 ] Heriot-Watt University Edinburgh, UK, EH14 4AS +44 (0)131 451 8283 http://www.macs.hw.ac.uk/~ek19/

1 0

Sublime2/3 hsdev patch: testers needed
by Scott Michel 13 Feb '17

13 Feb '17

Was wondering if there are any Sublime Text users out there who also use hsdev as their Haskell IDE backend. I'd recently (within the last 2 weeks) encountered random lockups, error messages about resources no longer available. I was able to track them down to half-closed pipes and ended up revamping subprocess interaction. So far, I have left a SublimeText session open for 3 days, done some fair amount of work and haven't had any problems. If you are a SublimeText 2/3 hsdev user and are comfortable with checking out Sublime packages directly from github, I could use some extra help shaking out the code to ensure that it is as robust as I think it is. The URL to my Github fork is: https://github.com/bscottm/SublimeHaskell.git Once you've cloned my fork, check out the 'stderr_stdout' branch and test away -- I'm looking for unexpected lockups (e.g., when you've saved a file and ST's status line says "... Checking and Linting" forever.) Thanks! -scooter

1 0

here's my solution for scripting/interpreter approach
by Dennis Raddle 13 Feb '17

13 Feb '17

My application needed the flexibility of writing test code and running it, or configuring its job (playback of music) through Haskell code and immediately testing the result (i.e. making sound and listening). I thought I would use GHCI, but I ran into some trouble. For one thing, my program forks a thread to do the timed control of the music, while the main thread implements a REPL-like "control loop" -- i.e. let me enter commands to influence the playback or halt it. I think this was crashing GHCI, perhaps when an interpreted script forks a thread which is still alive when control returns to the GHCI prompt. Not sure. Anyway here's what I did. Now the process that does real-time control of the playback is an entirely separate process. The control loop is started by me first, and depending on the command I enter, it builds the playback program with "ghc --make" and then spawns it. I send it signals from the control loop. This turns out to be great. I can make changes anywhere in my playback application, from the deepest utility library to the top-level configuration script, and it builds as needed before running. And, in the case it doesn't need to build anything, "ghc --make" finishes quickly so it doesn't feel inefficient to invoke it after every command I enter in the control loop. D

2 2

Re: [Haskell-cafe] Lenses and records and ecosystem
by Anthony Clayden 11 Feb '17

11 Feb '17

> ON 10/02/17 07:10, Tony Morris wrote: >> On 10/02/17 15:35, Anthony Clayden wrote: >> I see Simon PJ's comment here >> https://github.com/ghc-proposals/ghc-proposals/pull/6#issuecomment-277971802 >> and the lengthy discussions from different advocates. >> >> How much is it true there's a fractured "Haskell ecosystem" >> with 2 (3?) incompatible approaches: >> * H98 style labelled records with various extensions >> to ease the pain. >> * newtype-wrapped Lenses >> * 'raw' (unwrapped) Lenses > Yearss ago, many of us spent a long time > on different designs of lenses, ... > ... it would be foolish to concede that ground > for no significant benefit. Thanks Tony, but I don't understand: concede what ground? You're perhaps saying that one style of lenses is the 'right' one(?) I am asking if they can co-exist. > > Can you mix those three styles inside one program? > How much pain does it cause? > > Can you import libraries with a mix of styles? How does a > program cope? Why would you? For what practical purpose? A lens/a structure/a record is a means to an end. Applications that are putting/getting stuff are doing it for some purpose. Not merely because lenses are a nice application of category theory. So say you want to use the functionality from 3 different libraries, but each is written using a different style. >> >> I see the plethora of operators Lenses come with >> (mostly to keep the types coherent?). >> Except that Lens composition is plain function composition >> (.). >> >> I remember something from SPJ's video/lecture on Lenses: >> that having Lens composition turn out to be function >> composition is "cute". > The use of (.) here was deliberately designed that way to > assist in working against existing code. Is "against" some clever pun here? Like Concerto for Piano against Orchestra? Certainly (.) for lenses works 'backwards' (i.e. suffix style) compared to function-prefix style. (As any Lens tutorial will say.) >> That suggests to me it's more of a happy accident than a >> necessary feature. > Not necessary, just useful. I am less excited about this > feature than many others, but it is useful nonetheless, > and was specifically designed that way. Whether or not that's justified [**] it's counter-intuitive w.r.t. Haskell, so I don't see a need to use the same symbol. Hence my "wondering" below. >> >> I also see in the ORF proposal, OverloadedLabels part, >> that composing with Control.Category.(.) can lead to type >> ambiguity. >> >> I wonder: >> Could there be a dedicated operator for composing Lenses, >> that has the same semantics as (.), >> but a more specialised type? >> To strengthen type inference/reduce ambiguity. >> [**] the justification for postfix style seems to be so it's more like OO. Seems strange: FP just isn't very like OO. And in particular, functional data structures, just aren't like OO/procedural data structures. Anthony

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Re: [Haskell-cafe] Lenses and records and ecosystem
by Anthony Clayden 11 Feb '17

11 Feb '17

> 2017-02-11 09:30 UTC Fumiaki Kinoshita: > Are there any real cases that the polymorphism of > Control.Category.. becomes a real problem? I think > ambiguity rarely occurs on the kind (* -> * -> *). > Hi Fumiaki, the remark is here https://github.com/adamgundry/ghc-proposals/blob/overloaded-record-fields/p… The composition is: fooBar = #foo . #bar ... However, if labels are interpreted using IsLabel, the inferred type of fooBar is (Category cat, IsLabel "foo" (cat s t), IsLabel "bar" (cat r s)) => cat r t There's no FunDep on IsLabel (nor could there be). So `s` is ambiguous. Same as the classical (show . read). The usual type for raw/unwrapped Lenses is: type Lens s t a b = forall f. Functor f => (a -> f b) -> (s -> f t) Which is of kind (* -> * -> *), but you need to squint a bit. > > 2017-02-10 14:35 GMT+09:00 Anthony Clayden: > > > > > > I see the plethora of operators Lenses come with > > (mostly to keep the types coherent?). > > Except that Lens composition is plain function > > composition (.). > > > > I remember something from SPJ's video/lecture on Lenses: > > that having Lens composition turn out to be function > > composition is "cute". > > That suggests to me it's more of a happy accident than a > > necessary feature. > > > > I also see in the ORF proposal, OverloadedLabels part, > > that composing with Control.Category.(.) can lead to > > type ambiguity. > > > > I wonder: > > Could there be a dedicated operator for composing Lenses > > , that has the same semantics as (.), > > but a more specialised type? > > To strengthen type inference/reduce ambiguity. > > AntC

1 0

Lenses and records and ecosystem
by Anthony Clayden 11 Feb '17

11 Feb '17

I see Simon PJ's comment here https://github.com/ghc-proposals/ghc-proposals/pull/6#issuecomment-277971802 and the lengthy discussions from different advocates. How much is it true there's a fractured "Haskell ecosystem" with 2 (3?) incompatible approaches: * H98 style labelled records with various extensions to ease the pain. * newtype-wrapped Lenses * 'raw' (unwrapped) Lenses Can you mix those three styles inside one program? How much pain does it cause? Can you import libraries with a mix of styles? How does a program cope? I see the plethora of operators Lenses come with (mostly to keep the types coherent?). Except that Lens composition is plain function composition (.). I remember something from SPJ's video/lecture on Lenses: that having Lens composition turn out to be function composition is "cute". That suggests to me it's more of a happy accident than a necessary feature. I also see in the ORF proposal, OverloadedLabels part, that composing with Control.Category.(.) can lead to type ambiguity. I wonder: Could there be a dedicated operator for composing Lenses, that has the same semantics as (.), but a more specialised type? To strengthen type inference/reduce ambiguity. AntC

3 2

Lifting a value into a DataKind
by Ivan Lazar Miljenovic 09 Feb '17

09 Feb '17

Is it possible to automatically lift an arbitrary value into a type? i.e. I'm after a function of type `a -> Proxy (b :: a)`. More specifically, I'm wanting to be able to write a function that can convert an Enum (e.g. Bool or Ord) into such a Proxy, so I can actually write a function that looks like: `a -> (forall b. Proxy (b :: a) -> r) -> r` and use the `a` type as a selector value (to e.g. choose between type class instances). -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com http://IvanMiljenovic.wordpress.com

2 8

Typeclass constraints not inferred when defining a function
by Stephen Demos 09 Feb '17

09 Feb '17

Hi all, A professor showed me a function today that looks like this - `append = flip (foldr (:))` GHC spits back an error when this is compiled - ``` • Ambiguous type variable ‘t0’ arising from a use of ‘foldr’ prevents the constraint ‘(Foldable t0)’ from being solved. Relevant bindings include append :: t0 a -> [a] -> [a] (bound at test.hs:4:1) Probable fix: use a type annotation to specify what ‘t0’ should be. ``` It's obvious from this error message the problem is that the type GHC infers doesn't include the typeclass constraint. In this case, it's Foldable, but you can easily think of other situations where the same error comes up with different typeclasses (a silly example that comes to mind is `fmap (const [])`). It's pretty easy to fix this error by just providing a type for the function that is more specific than the one GHC infers. However, he showed me that defining the same function in ghci using a let binding doesn't yield the same error. In fact, when using `:t`, it shows that ghci successfully infers the typeclass constraint on the function - ``` > :t flip (foldr (:)) flip (foldr (:)) :: Foldable t => t a -> [a] -> [a] ``` I was wondering if anyone could explain this apparent discrepancy to me. Thanks! Stephen Demos

3 2

Cabal Conditional For Detecting GHCi
by aditya siram 09 Feb '17

09 Feb '17

Hi all, I was wondering if Cabal has a predicate which allows me to only enable options when running GHCi. The use-case is I have a set of `ghc-options` that I do *not* want enabled when I run `cabal repl` or `stack repl`. Ideally I'm looking for something along the lines of: if !repl ghc-options: ... -deech

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ESSLLI student session CFP: Deadline extended until Feb 14
by Andreas Abel 08 Feb '17

08 Feb '17

*Deadline Extension to February 14* *ESSLLI 2017 STUDENT SESSION* Held during the 29th European Summer School in Logic, Language and Information Toulouse, France, July 17-28, 2017 *NEW* *Deadline for submissions: February 14, 2017* https://easychair.org/conferences/?conf=stus2017 *ABOUT:* The Student Session of the 29th European Summer School in Logic, Language, and Information (ESSLLI) will take place in Toulouse, France, July 17th to 28th, 2017 (https://www.irit.fr/esslli2017/) We invite submissions of original, unpublished work from students in any area at the intersection of Logic & Language, Language & Computation, or Logic & Computation. Submissions will be reviewed by several experts in the field, and accepted papers will be presented orally or as posters and selected papers will appear in the Student Session proceedings by Springer. This is an excellent opportunity to receive valuable feedback from expert readers and to present your work to a diverse audience. *ORAL/POSTER PRESENTATIONS:* Note that there are two separate kinds of submissions, one for oral presentations and one for posters. This means that papers are directly submitted either as oral presentations or as poster presentations. Reviewing and ranking will be done separately. We particularly encourage submissions for posters, as they offer an excellent opportunity to present smaller research projects and research in progress. *SUBMISSION GUIDELINES:* Authors must be students, and submissions may be singly or jointly authored. Each author may submit at most one single and one jointly authored contribution. Submissions should not be longer than 8 pages for an oral presentation or 4 pages for a poster presentation (including examples and references). Submissions must be anonymous, without any identifying information. More detailed guidelines regarding submission can be found on the Student Session website: http://www2.sfs.uni-tuebingen.de/esslli-stus-2017/. *SPONSORSHIP AND PRIZES* As in previous years, Springer has kindly agreed to sponsor the ESSLLI student session. The best poster and best talk will be awarded Springer book vouchers of 500€ each. *FURTHER INFORMATION:* Please direct inquiries about submission procedures or other matters relating to the Student Session to johannes.wahle(a)uni-tuebingen.de and karoliina.lohiniva(a)unige.ch. ESSLLI 2017 will feature a wide range of foundational and advanced courses and workshops in all areas of Logic, Language, and Computation. For further information, including registration information and course listings, and for general inquiries about ESSLLI 2017, please consult the main ESSLLI 2017 page: https://www.irit.fr/esslli2017/. Kind regards, The ESSLLI 2017 Student Session Organization Committee Chairs: Johannes Wahle (Universität Tübingen) Karoliina Lohiniva (Université de Genève) LoCo co-chairs: Marie Farrell (National University of Ireland Maynooth) Herbert Lange (University of Gothenburg) LoLa co-chairs: Milica Denic (École normale supérieure de Paris) Mora Maldonado (École normale supérieure de Paris) LaCo co-chairs: Emmanuele Chersoni (Université d'Aix-Marseille) Jennifer Sikos (Universität Heidelberg) -- Andreas Abel <>< Du bist der geliebte Mensch. Department of Computer Science and Engineering Chalmers and Gothenburg University, Sweden andreas.abel(a)gu.se http://www.cse.chalmers.se/~abela/

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Network.Download stops after 10 downloads
by Stéphane Thibaud 08 Feb '17

08 Feb '17

I have tried the Network.Download library in order to download CSV files from Yahoo Finance, but after the 10th download every next download fails. Does Network.Download keep connections open? I did consume the result of the openURI function (even with deepseq). Any ideas? Thanks in advance! Stéphane

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Re: [Haskell-cafe] Monad transformer performance - Request to review benchmarking code + results
by Saurabh Nanda 07 Feb '17

07 Feb '17

Thanks for digging deeper, David. What exactly did you inline? Also, am I the only one losing my mind over this? It's such a straightforward use of available code structuring tools in Haskell. How come the compiler is not being smart about this OOB? -- Saurabh. On 29 Jan 2017 9:42 pm, "David Turner" <dct25-561bs(a)mythic-beasts.com> wrote: Here's the profiling summary that I got: COST CENTRE MODULE %time %alloc getOverhead Criterion.Monad 41.3 0.0 >>= Lucid.Base 19.2 41.6 makeElement.\.\ Lucid.Base 11.4 23.4 fromHtmlEscapedString Blaze.ByteString.Builder.Html.Utf8 7.9 14.9 >>= Data.Vector.Fusion.Util 2.3 1.7 return Lucid.Base 1.4 2.1 runBenchmark.loop Criterion.Measurement 1.2 0.0 with.\ Lucid.Base 1.0 2.1 foldlMapWithKey Lucid.Base 0.5 2.6 streamDecodeUtf8With.decodeChunk Data.Text.Encoding 0.0 1.7 As expected, HtmlT's bind is the expensive bit. However I've been unable to encourage it to go away using INLINE pragmas. On 29 January 2017 at 15:45, Oliver Charles <ollie(a)ocharles.org.uk> wrote: > I would start by inlining operations in the Functor, Applicative and Monad > classes for your monad and all the layers in the stack (such as HtmlT). An > un-inlining monadic bind can end up allocating a lot (as it's such a common > operation) > > On Sun, 29 Jan 2017, 3:32 pm Saurabh Nanda, <saurabhnanda(a)gmail.com> > wrote: > >> Please tell me what to INLINE. I'll update the benchmarks. >> >> Also, shouldn't this be treated as a GHC bug then? Using monad >> transformers as intended should not result in a severe performance penalty! >> Either monad transformers themselves are a problem or GHC is not doing the >> right thing. >> >> -- Saurabh. >> >> On 29 Jan 2017 7:50 pm, "Oliver Charles" <ollie(a)ocharles.org.uk> wrote: >> >> I would wager a guess that this can be solved with INLINE pragmas. We >> recently added INLINE to just about everything in transformers and got a >> significant speed up. >> >> On Sun, 29 Jan 2017, 11:18 am David Turner, < >> dct25-561bs(a)mythic-beasts.com> wrote: >> >> I would guess that the issue lies within HtmlT, which looks vaguely >> similar to a WriterT transformer but without much in the way of >> optimisation (e.g. INLINE pragmas). But that's just a guess after about 30 >> sec of glancing at https://hackage.haskell.org >> /package/lucid-2.9.7/docs/src/Lucid-Base.html so don't take it as gospel. >> >> My machine is apparently an i7-4770 of a similar vintage to yours, >> running Ubuntu in a VirtualBox VM hosted on Windows. 4GB of RAM in the VM, >> 16 in the host FWIW. >> >> >> On 29 Jan 2017 10:26, "Saurabh Nanda" <saurabhnanda(a)gmail.com> wrote: >> >> Thank you for the PR. Does your research suggest something is wrong with >> HtmlT when combined with any MonadIO, not necessarily ActionT? Is this an >> mtl issue or a lucid issue in that case? >> >> Curiously, what's your machine config? I'm on a late 2011 macbook pro >> with 10G ram and some old i5. >> >> -- Saurabh. >> >> On 29 Jan 2017 3:05 pm, "David Turner" <dct25-561bs(a)mythic-beasts.com> >> wrote: >> >> The methodology does look reasonable, although I think you should wait >> for all the scotty threads to start before starting the benchmarks, as I >> see this interleaved output: >> >> Setting phasers to stun... (port 3002) (ctrl-c to quit) >> Setting phasers to stun... (port 3003) (ctrl-c to quit) >> Setting phasers to stun... (port 3001) (ctrl-c to quit) >> benchmarking bareScotty >> Setting phasers to stun... (port 3000) (ctrl-c to quit) >> >> Your numbers are wayyy slower than the ones I see on my dev machine: >> >> benchmarking bareScotty >> Setting phasers to stun... (port 3000) (ctrl-c to quit) >> time 10.94 ms (10.36 ms .. 11.52 ms) >> 0.979 R² (0.961 R² .. 0.989 R²) >> mean 12.53 ms (11.98 ms .. 13.28 ms) >> std dev 1.702 ms (1.187 ms .. 2.589 ms) >> variance introduced by outliers: 66% (severely inflated) >> >> benchmarking bareScottyBareLucid >> time 12.95 ms (12.28 ms .. 13.95 ms) >> 0.972 R² (0.951 R² .. 0.989 R²) >> mean 12.20 ms (11.75 ms .. 12.69 ms) >> std dev 1.236 ms (991.3 μs .. 1.601 ms) >> variance introduced by outliers: 50% (severely inflated) >> >> benchmarking transScottyBareLucid >> time 12.05 ms (11.70 ms .. 12.39 ms) >> 0.992 R² (0.982 R² .. 0.996 R²) >> mean 12.43 ms (12.06 ms .. 13.01 ms) >> std dev 1.320 ms (880.5 μs .. 2.071 ms) >> variance introduced by outliers: 54% (severely inflated) >> >> benchmarking transScottyTransLucid >> time 39.73 ms (32.16 ms .. 49.45 ms) >> 0.668 R² (0.303 R² .. 0.969 R²) >> mean 42.59 ms (36.69 ms .. 54.38 ms) >> std dev 16.52 ms (8.456 ms .. 25.96 ms) >> variance introduced by outliers: 92% (severely inflated) >> >> benchmarking bareScotty >> time 11.46 ms (10.89 ms .. 12.07 ms) >> 0.986 R² (0.975 R² .. 0.994 R²) >> mean 11.73 ms (11.45 ms .. 12.07 ms) >> std dev 800.6 μs (636.8 μs .. 975.3 μs) >> variance introduced by outliers: 34% (moderately inflated) >> >> but nonetheless I do also see the one using renderTextT to be >> substantially slower than the one without. >> >> I've sent you a PR [1] that isolates Lucid from Scotty and shows that >> renderTextT is twice as slow over IO than it is over Identity, and it's >> ~10% slower over Reader too: >> >> benchmarking renderText >> time 5.529 ms (5.328 ms .. 5.709 ms) >> 0.990 R² (0.983 R² .. 0.995 R²) >> mean 5.645 ms (5.472 ms .. 5.888 ms) >> std dev 593.0 μs (352.5 μs .. 908.2 μs) >> variance introduced by outliers: 63% (severely inflated) >> >> benchmarking renderTextT Id >> time 5.439 ms (5.243 ms .. 5.640 ms) >> 0.991 R² (0.985 R² .. 0.996 R²) >> mean 5.498 ms (5.367 ms .. 5.631 ms) >> std dev 408.8 μs (323.8 μs .. 552.9 μs) >> variance introduced by outliers: 45% (moderately inflated) >> >> benchmarking renderTextT Rd >> time 6.173 ms (5.983 ms .. 6.396 ms) >> 0.990 R² (0.983 R² .. 0.995 R²) >> mean 6.284 ms (6.127 ms .. 6.527 ms) >> std dev 581.6 μs (422.9 μs .. 773.0 μs) >> variance introduced by outliers: 55% (severely inflated) >> >> benchmarking renderTextT IO >> time 12.35 ms (11.84 ms .. 12.84 ms) >> 0.989 R² (0.982 R² .. 0.995 R²) >> mean 12.22 ms (11.85 ms .. 12.76 ms) >> std dev 1.159 ms (729.5 μs .. 1.683 ms) >> variance introduced by outliers: 50% (severely inflated) >> >> I tried replacing >> >> forM [1..10000] (\_ -> div_ "hello world!") >> >> with >> >> replicateM_ 10000 (div_ "hello world!") >> >> which discards the list of 10,000 () values that the forM thing >> generates, but this made very little difference. >> >> Hope this helps, >> >> David >> >> >> [1] https://github.com/vacationlabs/monad-transformer-benchmark/pull/2 >> >> >> >> On 29 January 2017 at 07:26, Saurabh Nanda <saurabhnanda(a)gmail.com> >> wrote: >> >> Hi, >> >> I was noticing severe drop in performance when Lucid's HtmlT was being >> combined with Scotty's ActionT. I've tried putting together a minimal repro >> at https://github.com/vacationlabs/monad-transformer-benchmark Request >> someone with better knowledge of benchmarking to check if the benchmarking >> methodology is correct. >> >> Is my reading of 200ms performance penalty correct? >> >> -- Saurabh. >> >> >> _______________________________________________ >> Haskell-Cafe mailing list >> To (un)subscribe, modify options or view archives go to: >> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe >> Only members subscribed via the mailman list are allowed to post. >> >> >> >> >> _______________________________________________ >> Haskell-Cafe mailing list >> To (un)subscribe, modify options or view archives go to: >> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe >> Only members subscribed via the mailman list are allowed to post. >> >> >>

3 7

Cleanup obsolete stack stuff (compiler, libraries, etc.)
by Geraldus 06 Feb '17

06 Feb '17

Hi folks! I want to perform some cleanup deleting obsolete compilers located in ~/.stack folder. I know stack places them into ~/.stack/programs/<platform>/ directory, however I think there are also should be something else related, e.g. docs and libs, and especially packages that was built when I used old LTS snapshots. What is the best way to perform such cleanup?

3 3

Removing Hackage packages
by aditya siram 05 Feb '17

05 Feb '17

Hi, I'd like to remove a couple of my packages [1] from Hackage. How do I do that? Thanks! -deech [1] http://hackage.haskell.org/package/fltkhs-demos, http://hackage.haskell.org/package/fltkhs-fluid-demos

2 2

ghci, running :load on filename provided by variable
by Dennis Raddle 04 Feb '17

04 Feb '17

How do I load a file in ghci where the filename comes from a variable? So like, let f = "myfile.hs" :load f D

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Getting added to the Haskell group on Github.
by aditya siram 04 Feb '17

04 Feb '17

Hi, Some time ago the maintainership of c2hs [1] was silently passed to me. However I am unable to request access to the repo because I am not on the Haskell team [2]. Apparently I have to be added by someone already on the team but I'm having trouble getting in touch with someone. If anyone reading this is on the team [2] please add me. I'm @deech on Github. Thanks! -deech [1] https://github.com/haskell/c2hs [2] https://github.com/orgs/haskell/people

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Purpose of Control.Monad.Base class
by Guru Devanla 04 Feb '17

04 Feb '17

Hello, I am trying to understand the purpose of the MonadBase class. https://hackage.haskell.org/package/transformers-base-0.4.4/docs/Control-Mo… Google search did not give me any helpful answers. Please could some one help me understand the purpose of this class and also point me to any good resources. Thanks Guru

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using ghci with compiled code
by Dennis Raddle 04 Feb '17

04 Feb '17

I want to use ghci to interpret parts of my program, and I would like it to pick up pre-compiled object files to speed things up in other parts. Right now whenever I launch ghci it seems to "compile" everything (I think to byte code).. what can I do? D

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Best way to provide monad transformer instances in library design?
by Matt 03 Feb '17

03 Feb '17

I'm writing a wrapper around ekg which provides an MTL-style class for recording metrics [1], and now I'm trying to figure out how to make the class usable for clients. I'm conflicted on the numerous ways to approach the problem. I would like to provide the best UX for the library, and want to consider viewpoints other than my own. Currently, the class is: class MonadMetrics m where getMetrics :: m Metrics I currently don't provide any concrete transformer, instead requiring that users define it for their own stacks. I'd like to make it easier to use. I can provide a concrete transformer newtype MetricT m a = MetricT (ReaderT Metrics m a) instance Monad m => MonadMetrics (MetricT m) where getMetrics = MetricT ask and then provide a wide variety of pass through instances. This approach requires a large amount of boilerplate, and for any instances I forget to provide, will require that clients make their own orphan instances. It also incurs additional dependencies just for writing instances. I can provide a more abstract transformer and a more general Metrics class: class HasMetrics r where metrics :: Lens' r Metrics newtype MetricT2 m a = MetricT2 (m a) instance (MonadReader r m, HasMetrics r) => MonadMetrics (MetricT2 m) where getMetrics = MetricT (view metrics) but this still requires those pass through instances. Finally, I can scrap `MonadMetrics` as anything other than a class alias: class (MonadReader r m, MonadIO m, HasMetrics r) => MonadMetrics r m instance (MonadReader r m, MonadIO m, HasMetrics r) => MonadMetrics r m but now I have UndecidableInstances and a multiparam type class, and I'm not sure how well this actually plays out in the wild. What are your thoughts on this issue? Matt Parsons [1]: https://github.com/sellerlabs/monad-metrics

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segfault with Hint (InterpreterT)
by Dennis Raddle 03 Feb '17

03 Feb '17

My program segfaults the second time it run runInterpreterT. Just wondering if that's not supposed to be allowed. I'm actually not sure what triggers the segfault -- it's also doing some MIDI I/O. D

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is there less available support for beginners these days?
by Dennis Raddle 03 Feb '17

03 Feb '17

I'm a Haskell hobbyist enthusiast -- first learned it in 2008, struggling having come from an imperative language background, and I only get to use it in hobby projects, but I love it more each year. I still consider myself a beginner in many areas. Unfortunately it used to be much easier to get responses on the beginner's list or the #haskell channel. I've now had several posts go completely unanswered on the beginner's list, and can't get help from #haskell most of the time (by "help" I mean someone who takes just a few minutes with me). I've tried posting on Haskell cafe in the hopes I would get more responses and I'm not sure if that's going to work (or is appropriate). D

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Project hosting platform - looking for new developer
by fr33domlover 03 Feb '17

03 Feb '17

(tl;dr Git and Darcs hosting platform with planned federation written in Yesod, I'm looking for someone excited about the idea to take over development) Hello Haskellers, Several months ago I started developing a project hosting platform called Vervis. It's written in Haskell using the Yesod web framework. The intention was to make it federated and allow people for the first time in git (and darcs) history to enjoy both the full access to the community and avoid the proprietaryness and centralization of githu8. I'm probably still really a beginner and I never made any web application before Vervis, or even an actual mature stable software project. But I made huge progress with Vervis very fast, and I created something you can actually see with your eyes :) However due to certain life preferences I stopped working on it and I may never go back to it. But I was hoping someone else would want to continue its development. The code is hosted both at Darcs Hub and in a Vervis instance, so the project is self-hosting: https://dev.seek-together.space/s/fr33domlover/r/vervis I didn't work on design much, just focused on functionality. Among the unique features already present one one way or another: - Supports both Git and Darcs - Rendering of documents using Pandoc, supporting more formats and variants than any other platform could - Support of Libravatar for user avatar images - Flexible integrated system for project management and issues, on the level you can find in project management platforms, but here it's integrated into the code hosting platform itself - Hierarchical discussion threads - A single project can contain more than one repo, i.e. repos can share the same project plan and the same issue database - Merely being written in Haskell and Yesod makes it very stable once it builds successfully There are still many quirks, including the UI of the registration system and UI in general, so I'm sorry in advance if you try to create an account there and get errors or confusing UIs. It's not polished or anything yet. I also made several support projects and implemented some helper tools, such as some support for parsing darcs repos (attoparsec stuff that can and maybe should be merged into Darcs itself), SSH server component that uses an improved version of the ssh package, hierarchical SQL query API with an interface similar to the FGL library, code for working with git repos... and probably more things I'm forgetting. If you have any questions, I'm here to answer :) --fr33

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Haskell jobs in Brisbane, Australia
by Tony Morris 01 Feb '17

01 Feb '17

Hi all, Data61, CSIRO has recently announced three new positions in Brisbane, Australia for work in FP. Haskell will be the primary language used. For a few reasons remote work is not available for these positions, but if you’re willing to relocate, these would be a fantastic opportunity. https://jobs.csiro.au/job/Brisbane%2C-QLD-Senior-Functional-Programming-Eng… https://jobs.csiro.au/job/Brisbane%2C-QLD-Functional-Programming-Engineers/… https://jobs.csiro.au/job/Brisbane%2C-QLD-Functional-Programming-Engineer/3…

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Second Call for Papers: ICFP 2017
by Lindsey Kuper 01 Feb '17

01 Feb '17

ICFP 2017 The 22nd ACM SIGPLAN International Conference on Functional Programming Oxford, United Kingdom http://icfp17.sigplan.org/ Second Call for Papers ### Important dates Submissions due: Monday, February 27, Anywhere on Earth https://icfp17.hotcrp.com Author response: Monday, April 17, 2017, 15:00 (UTC) - Thursday, April 20, 2017, 15:00 (UTC) Notification: Monday, 1 May, 2017 Final copy due: Monday, 5 June 2017 Early registration: TBA Conference: Monday, 4 September - Wednesday, 6 September, 2017 ### Updates for Second Call for Papers This revision, published January 31, 2017, includes the following updates: * A link to the list of frequently asked questions about the double-blind review process. * A new requirement for citations in author-year format. This follows a decision for PACMPL that was made after the original version of this call was distributed. As such, author-year format will be required for final (accepted) versions of papers in ICFP 2017, but not for submissions. * Additional guidance for authors using LaTeX. * A clarification about the expectations for author attendance in the event of visa-related problems. ### New this year Those familiar with previous ICFP conferences should be aware of two significant changes that are being introduced in 2017: 1. Papers selected for ICFP 2017 will be published as the ICFP 2017 issue of a new journal, Proceedings of the ACM on Programming Languages (PACMPL), which replaces the previous ICFP conference proceedings. The move to PACMPL will have two noticeable impacts on authors: * A new, two-phase selection and reviewing process that conforms to ACM’s journal reviewing guidelines. * A new, single-column format for submissions. 2. Authors of papers that are conditionally accepted in the first phase of the reviewing process will have the option to submit materials for Artifact Evaluation. Further details on each of these changes are included in the following text. ### Scope ICFP 2017 seeks original papers on the art and science of functional programming. Submissions are invited on all topics from principles to practice, from foundations to features, and from abstraction to application. The scope includes all languages that encourage functional programming, including both purely applicative and imperative languages, as well as languages with objects, concurrency, or parallelism. Topics of interest include (but are not limited to): * *Language Design*: concurrency, parallelism, and distribution; modules; components and composition; metaprogramming; type systems; interoperability; domain-specific languages; and relations to imperative, object-oriented, or logic programming. * *Implementation*: abstract machines; virtual machines; interpretation; compilation; compile-time and run-time optimization; garbage collection and memory management; multi-threading; exploiting parallel hardware; interfaces to foreign functions, services, components, or low-level machine resources. * *Software-Development Techniques*: algorithms and data structures; design patterns; specification; verification; validation; proof assistants; debugging; testing; tracing; profiling. * *Foundations*: formal semantics; lambda calculus; rewriting; type theory; monads; continuations; control; state; effects; program verification; dependent types. * *Analysis and Transformation*: control-flow; data-flow; abstract interpretation; partial evaluation; program calculation. * *Applications*: symbolic computing; formal-methods tools; artificial intelligence; systems programming; distributed-systems and web programming; hardware design; databases; XML processing; scientific and numerical computing; graphical user interfaces; multimedia and 3D graphics programming; scripting; system administration; security. * *Education*: teaching introductory programming; parallel programming; mathematical proof; algebra. Submissions will be evaluated according to their relevance, correctness, significance, originality, and clarity. Each submission should explain its contributions in both general and technical terms, clearly identifying what has been accomplished, explaining why it is significant, and comparing it with previous work. The technical content should be accessible to a broad audience. ICFP 2017 also welcomes submissions in two separate categories --- Functional Pearls and Experience Reports --- that must be marked as such at the time of submission and that need not report original research results. Detailed guidelines on both categories are given at the end of this call. Please contact the program chair if you have questions or are concerned about the appropriateness of a topic. ### Preparation of submissions ICFP 2017 will employ a lightweight double-blind reviewing process, as described below. **Deadline**: The deadline for submissions is Monday, February 27, 2017, Anywhere on Earth (<https://en.wikipedia.org/wiki/Anywhere_on_Earth>). This deadline will be strictly enforced. **Formatting**: (NOTE: NEW FORMAT REQUIREMENTS FOR ICFP 2017) Submissions must be in PDF format, printable in black and white on US Letter sized paper, and interpretable by common PDF tools. All submissions must adhere to the "ACM Large" template that is available (in both LaTeX and Word formats) from <http://www.acm.org/publications/proceedings-template>. For authors using LaTeX, a lighter-weight package, including only the essential files, is available from <http://sigplan.org/Resources/Author/#acmart-format>; the appropriate template for ICFP 2017 authors is in the file `acmart-pacmpl-template.tex`. As documented in the template, submissions should be prepared using the `acmlarge` and `anonymous` options. The use of the `review` option is also strongly encouraged but not required. (The `review` option will add line numbers, which will make it easier for reviewers to reference specific parts of your paper in their comments, but should have absolutely no other effect on the typesetting.) Details of available technical support for LaTeX-specific questions is available at <http://www.acm.org/publications/proceedings-template#h-technical-support>. There is a limit of 24 pages for a full paper or 12 pages for an Experience Report; in either case, the bibliography will not be counted against these limits. These page limits have been chosen to allow essentially the same amount of content with the new single-column format as was possible with the two-column format used in past ICFP conferences. Submissions that exceed the page limits or, for other reasons, do not meet the requirements for formatting, will be summarily rejected. **Citations**: As part of PACMPL, ICFP 2017 papers are expected to use author-year citations for references to other work. Author-year citations may be used as either a noun phrase, such as "The lambda calculus was originally conceived by Church (1932)", or a parenthetic phase, such as "The lambda calculus (Church 1932) was intended as a foundation for mathematics". A useful test for correct usage it to make sure that the text still reads correctly when the parenthesized portions of any references are omitted. Take care with prepositions; in the first example above, "by" is more appropriate than "in" because it allows the text to be read correctly as a reference to the author. Sometimes, readability may be improved by putting parenthetic citations at the end of a clause or a sentence, such as "A foundation for mathematics was provided by the lambda calculus (Church 1932)". In LaTeX, use `\citet{Church-1932}` for citations as a noun phrase, "Church (1932)", and `\citep{Church-1932}` for citations as a parenthetic phrase, "(Church 1932)"; for details, see Sections 2.3--2.5 of the natbib documentation (<http://ctan.org/pkg/natbib>). **Submission**: Submissions will be accepted at <https://icfp17.hotcrp.com/> (in preparation at the time of writing). Improved versions of a paper may be submitted at any point before the submission deadline using the same web interface. **Author Response Period**: Authors will have a 72-hour period, starting at 15:00 UTC on Monday, April 17, 2017, to read reviews and respond to them. **Supplementary Materials**: Authors have the option to attach supplementary material to a submission, on the understanding that reviewers may choose not to look at it. The material should be uploaded at submission time, as a single pdf or a tarball, not via a URL. This supplementary material may or may not be anonymized; if not anonymized, it will only be revealed to reviewers after they have submitted their review of the paper and learned the identity of the author(s). **Authorship Policies**: All submissions are expected to comply with the ACM Policies for Authorship that are detailed at <https://www.acm.org/publications/authors/information-for-authors>. **Republication Policies**: Each submission must adhere to SIGPLAN's republication policy, as explained on the web at <http://www.sigplan.org/Resources/Policies/Republication>. **Resubmitted Papers**: Authors who submit a revised version of a paper that has previously been rejected by another conference have the option to attach an annotated copy of the reviews of their previous submission(s), explaining how they have addressed these previous reviews in the present submission. If a reviewer identifies him/herself as a reviewer of this previous submission and wishes to see how his/her comments have been addressed, the program chair will communicate to this reviewer the annotated copy of his/her previous review. Otherwise, no reviewer will read the annotated copies of the previous reviews. ### Review Process This section outlines the two-stage process with lightweight double-blind reviewing that will be used to select papers for presentation at ICFP 2017. A [list of frequently asked questions and answers](http://icfp17.sigplan.org/track/icfp-2017-papers#Submission-and-Re… that address common concerns is available on the conference website and will be updated as necessary to clarify and expand on this process. **ICFP 2017 will employ a two-stage review process.** The first stage in the review process will assess submitted papers using the criteria stated above and will allow for feedback and input on initial reviews through the author response period mentioned previously. At the PC meeting, a set of papers will be conditionally accepted and all other papers will be rejected. Authors will be notified of these decisions on May 1, 2017. Authors of conditionally accepted papers will be provided with committee reviews (just as in previous conferences) along with a set of mandatory revisions. After five weeks (June 5, 2017), the authors will provide a second submission. The second and final reviewing phase assesses whether the mandatory revisions have been adequately addressed by the authors and thereby determines the final accept/reject status of the paper. The intent and expectation is that the mandatory revisions can be addressed within five weeks and hence that conditionally accepted papers will in general be accepted in the second phase. The second submission should clearly identify how the mandatory revisions were addressed. To that end, the second submission must be accompanied by a cover letter mapping each mandatory revision request to specific parts of the paper. The cover letter will facilitate a quick second review, allowing for confirmation of final acceptance within two weeks. Conversely, the absence of a cover letter will be grounds for the paper’s rejection. This process is intended as a refinement of the review process that has been used in previous ICFP conferences. By incorporating a second stage, the process will conform to ACM’s journal reviewing guidelines for PACMPL. **ICFP 2017 will employ a lightweight double-blind reviewing process.** To facilitate this, submitted papers must adhere to two rules: 1. **author names and institutions must be omitted**, and 2. **references to authors' own related work should be in the third person** (e.g., not "We build on our previous work ..." but rather "We build on the work of ..."). The purpose of this process is to help the PC and external reviewers come to an initial judgement about the paper without bias, not to make it impossible for them to discover the authors if they were to try. Nothing should be done in the name of anonymity that weakens the submission or makes the job of reviewing the paper more difficult (e.g., important background references should not be omitted or anonymized). In addition, authors should feel free to disseminate their ideas or draft versions of their paper as they normally would. For instance, authors may post drafts of their papers on the web or give talks on their research ideas. ### Information for Authors of Accepted Papers * As a condition of acceptance, final versions of all papers must adhere to the new ACM Large format. The page limits for final versions of papers will be increased to ensure that authors have space to respond to reviewer comments and mandatory revisions. * Authors of accepted submissions will be required to agree to one of the three ACM licensing options: copyright transfer to ACM; retaining copyright but granting ACM exclusive publication rights; or open access on payment of a fee. Further information about ACM author rights is available from <http://authors.acm.org>. * At least one author of each accepted submission will be expected to attend and present their paper at the conference. (ICFP welcomes all authors, regardless of nationality. If any author of an accepted submission has visa-related difficulties in travelling to the conference, we will make arrangements to enable remote participation, and not require them to attend the conference in order to present their talk.) The schedule for presentations will be determined and shared with authors after the full program has been selected. Presentations will be videotaped and released online if the presenter consents. * We intend that the proceedings will be freely available for download from the ACM Digital Library in perpetuity via the OpenTOC mechanism. * ACM Author-Izer is a unique service that enables ACM authors to generate and post links on either their home page or institutional repository for visitors to download the definitive version of their articles from the ACM Digital Library at no charge. Downloads through Author-Izer links are captured in official ACM statistics, improving the accuracy of usage and impact measurements. Consistently linking to the definitive version of an ACM article should reduce user confusion over article versioning. After an article has been published and assigned to the appropriate ACM Author Profile pages, authors should visit <http://www.acm.org/publications/acm-author-izer-service> to learn how to create links for free downloads from the ACM DL. * **AUTHORS TAKE NOTE: The official publication date is the date the proceedings are made available in the ACM Digital Library. This date may be up to *two weeks prior* to the first day of the conference. The official publication date affects the deadline for any patent filings related to published work.** ### Artifact Evaluation Authors of papers that are conditionally accepted in the first phase of the review process will be encouraged (but not required) to submit supporting materials for Artifact Evaluation. These items will then be reviewed by a committee, separate from the program committee, whose task is to assess how the artifacts support the work described in the associated paper. Papers that go through the Artifact Evaluation process successfully will receive a seal of approval printed on the papers themselves. Authors of accepted papers will be encouraged to make the supporting materials publicly available upon publication of the proceedings, for example, by including them as "source materials" in the ACM Digital Library. An additional seal will mark papers whose artifacts are made available, as outlined in the ACM guidelines for artifact badging. Participation in Artifact Evaluation is voluntary and will not influence the final decision regarding paper acceptance. Further information about the motivations and expectations for Artifact Evaluation can be found at <http://icfp17.sigplan.org/track/icfp-2017-Artifacts>. ### Special categories of papers In addition to research papers, ICFP solicits two kinds of papers that do not require original research contributions: Functional Pearls, which are full papers, and Experience Reports, which are limited to half the length of a full paper. Authors submitting such papers should consider the following guidelines. #### Functional Pearls A Functional Pearl is an elegant essay about something related to functional programming. Examples include, but are not limited to: * a new and thought-provoking way of looking at an old idea * an instructive example of program calculation or proof * a nifty presentation of an old or new data structure * an interesting application of functional programming techniques * a novel use or exposition of functional programming in the classroom While pearls often demonstrate an idea through the development of a short program, there is no requirement or expectation that they do so. Thus, they encompass the notions of theoretical and educational pearls. Functional Pearls are valued as highly and judged as rigorously as ordinary papers, but using somewhat different criteria. In particular, a pearl is not required to report original research, but, it should be concise, instructive, and entertaining. A pearl is likely to be rejected if its readers get bored, if the material gets too complicated, if too much specialized knowledge is needed, or if the writing is inelegant. The key to writing a good pearl is polishing. A submission that is intended to be treated as a pearl must be marked as such on the submission web page, and should contain the words "Functional Pearl" somewhere in its title or subtitle. These steps will alert reviewers to use the appropriate evaluation criteria. Pearls will be combined with ordinary papers, however, for the purpose of computing the conference's acceptance rate. #### Experience Reports The purpose of an Experience Report is to help create a body of published, refereed, citable evidence that functional programming really works --- or to describe what obstacles prevent it from working. Possible topics for an Experience Report include, but are not limited to: * insights gained from real-world projects using functional programming * comparison of functional programming with conventional programming in the context of an industrial project or a university curriculum * project-management, business, or legal issues encountered when using functional programming in a real-world project * curricular issues encountered when using functional programming in education * real-world constraints that created special challenges for an implementation of a functional language or for functional programming in general An Experience Report is distinguished from a normal ICFP paper by its title, by its length, and by the criteria used to evaluate it. * Both in the proceedings and in any citations, the title of each accepted Experience Report must begin with the words "Experience Report" followed by a colon. The acceptance rate for Experience Reports will be computed and reported separately from the rate for ordinary papers. * Experience Report submissions can be at most 12 pages long, excluding bibliography. * Each accepted Experience Report will be presented at the conference, but depending on the number of Experience Reports and regular papers accepted, authors of Experience reports may be asked to give shorter talks. * Because the purpose of Experience Reports is to enable our community to accumulate a body of evidence about the efficacy of functional programming, an acceptable Experience Report need not add to the body of knowledge of the functional-programming community by presenting novel results or conclusions. It is sufficient if the Report states a clear thesis and provides supporting evidence. The thesis must be relevant to ICFP, but it need not be novel. The program committee will accept or reject Experience Reports based on whether they judge the evidence to be convincing. Anecdotal evidence will be acceptable provided it is well argued and the author explains what efforts were made to gather as much evidence as possible. Typically, more convincing evidence is obtained from papers which show how functional programming was used than from papers which only say that functional programming was used. The most convincing evidence often includes comparisons of situations before and after the introduction or discontinuation of functional programming. Evidence drawn from a single person's experience may be sufficient, but more weight will be given to evidence drawn from the experience of groups of people. An Experience Report should be short and to the point: it should make a claim about how well functional programming worked on a particular project and why, and produce evidence to substantiate this claim. If functional programming worked in this case in the same ways it has worked for others, the paper need only summarize the results --- the main part of the paper should discuss how well it worked and in what context. Most readers will not want to know all the details of the project and its implementation, but the paper should characterize the project and its context well enough so that readers can judge to what degree this experience is relevant to their own projects. The paper should take care to highlight any unusual aspects of the project. Specifics about the project are more valuable than generalities about functional programming; for example, it is more valuable to say that the team delivered its software a month ahead of schedule than it is to say that functional programming made the team more productive. If the paper not only describes experience but also presents new technical results, or if the experience refutes cherished beliefs of the functional-programming community, it may be better off submitted it as a full paper, which will be judged by the usual criteria of novelty, originality, and relevance. The program chair will be happy to advise on any concerns about which category to submit to. ### Organizers General Chair: Jeremy Gibbons (University of Oxford, UK) Program Chair: Mark Jones (Portland State University, USA) Artifact Evaluation Chair: Ryan R. Newton (Indiana University, USA) Industrial Relations Chair: Ryan Trinkle (Obsidian Systems LLC, USA) Programming Contest Organiser: Sam Lindley (University of Edinburgh, UK) Publicity and Web Chair: Lindsey Kuper (Intel Labs, USA) Student Research Competition Chair: Ilya Sergey (University College London, UK) Video Chair: Jose Calderon (Galois, Inc., USA) Workshops Co-Chair: Andres Löh (Well-Typed LLP) Workshops Co-Chair: David Christiansen (Indiana University, USA) Program Committee: Bob Atkey (University of Strathclyde, Scotland) Adam Chlipala (MIT, USA) Dominique Devriese (KU Leuven, Belgium) Martin Erwig (Oregon State, USA) Matthew Flatt (University of Utah, USA) Ronald Garcia (University of British Columbia, Canada) Kathryn Gray (University of Cambridge, England) John Hughes (Chalmers University and Quvik, Sweden) Chung-Kil Hur (Seoul National University, Korea) Graham Hutton (University of Nottingham, England) Alan Jeffrey (Mozilla Research, USA) Ranjit Jhala (University of California, San Diego, USA) Shin-ya Katsumata (Kyoto University, Japan) Lindsey Kuper (Intel Labs, USA) Dan Licata (Wesleyan University, USA) Ben Lippmeier (Digital Asset, Australia) Gabriel Scherer (Northeastern University, USA) Alexandra Silva (University College London, England) Nikhil Swamy (Microsoft Research, USA) Sam Tobin-Hochstadt (Indiana University, USA) Nicolas Wu (University of Bristol, England) Beta Ziliani (CONICET and FAMAF, Universidad Nacional de Córdoba, Argentina)

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Ensuring all values of an ADT are explicitly handled OR finding all occurrences of type X in my app
by Saurabh Nanda 01 Feb '17

01 Feb '17

Hi, If I have the following ADT data BookingState = Confirmed | Cancelled which had a very high chance of being expanded in the future to have more values. How do I ensure that every pattern match on BookingState matches each value explicitly. Basically prevent the '_' matcher ? If that is not possible, is the following possible instead: evolve BookingState and then find all possible occurrences of values of BookingState throughout my app? I'm basically trying to make sure that any a newly added state, which may require special-case handling is not automatically handled by the '_' branch. -- Saurabh.

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