- Haskell-Cafe - Haskell.org

Announcing Blocks for CodeWorld
by Stefan 01 Jul '16

01 Jul '16

Hi everyone, (this is somewhat cross-posted from reddit) I'm announcing Blocks for CodeWorld, which is a functional based drag-and-drop programming environment. The project is part of Haskell Summer of Code. The aim of the project is to create a web application with which users can drag-and-drop blocks in order to create CodeWorld <https://code.world/> applications, The project is primarily educational based, and more advanced applications may be created with the regular CodeWorld text UI. The application uses Blockly to allow users to drag-and-drop blocks, which can then be snapped together in order to build programs, in a Scratch-esque manner. The generated code is Haskell, which is then sent to the regular CodeWorld server and compiled with GHCJS, the resulting JavaScript is then run on the site. Code is generated as students are introduced to programming concepts with the Blocks and will later be exposed to a more text based environment. The majority of the code, aside from Blockly, is in Haskell, which is compiled to JavaScript using GHCJS. Currently, in this initial release, the user is able to: - Build and run simple CodeWorld programs, mostly pictures and transformations thereof - Save and Load projects, load a program by its URL. - Use polymorphic blocks, such as an if-then-else block and some others - Use Let definition blocks to create top level bindings Later, more advanced functional features such as pattern matching and some support for first-class functions might be covered. For anyone interested, an initial version can be found at code.world/blocks. If you want to follow on the progress you can check out my blog <http://stefanj.me/funblocks/>.

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Re: [Haskell-cafe] Help to choose a library name
by Corentin Dupont 29 Jun '16

29 Jun '16

Wow, it is very impressive. I need to give it more time. I have one question regarding this example: main = keep $ do th <- liftIO myThreadId -- thread 89 r <- async (do threadDelay 1000000; return "hello") -- thread 90 <|> async (return "world") -- thread 91 th' <- liftIO myThreadId -- thread 90 and 91 liftIO $ print (th, th', r) -- thread 90 and 91 Output: (ThreadId 89,ThreadId 91,"world") (ThreadId 89,ThreadId 90,"hello") For me it's counter-intuitive that there are two outputs. What is the reason behind? It seems that the use of the <|> affects the rest of the program. It looks strange to me because the two lines situated after the <|> does not look "syntactically" involved, if you see what I mean. Instead I was expecting only one output, with the first thread to finish "wins". In fact I implemented it like that: http://www.corentindupont.info/blog/posts/Programming/2014-09-23-Nomyx-Lang… Cheers Corentin On Mon, Jun 27, 2016 at 8:22 PM, Geraldus <heraldhoi(a)gmail.com> wrote: > Sorry, here is some links: > Wiki paga on GitHub > https://github.com/agocorona/transient/wiki/Transient-tutorial > Programming at specification level > https://github.com/agocorona/transient/wiki/Programming-at-the-specificatio… > > пн, 27 июн. 2016 г. в 23:19, Geraldus <heraldhoi(a)gmail.com>: > >> Hi! Have you looked at Transient by Alberto Gomez Corona? >> >> пн, 27 июн. 2016 г. в 18:27, Corentin Dupont <corentin.dupont(a)gmail.com>: >> >>> Hi Joachim, >>> I agree... I looked hard at them :) >>> https://wiki.haskell.org/Functional_Reactive_Programming >>> >>> I need a library with a DSL able to create forms on the fly, in a >>> "demand driven" way. >>> I.e. if at some point in time the user program needs a boolean from the >>> user, a radio button will be created on the screen of that user. The >>> objective is to retrieve the boolean, creating the form is just a way to do >>> that. Complex forms can be created, capable of generating full ADTs. The >>> styling of the form is not important. >>> Other requirements: >>> - it should be possible to run the event DSL in a monad different from >>> IO. >>> - the event DSL need to be instance of Alternative: events can be put in >>> concurrence, the first to fire wins. >>> >>> >>> >>> >>> On Mon, Jun 27, 2016 at 10:25 AM, Joachim Breitner < >>> mail(a)joachim-breitner.de> wrote: >>> >>>> Hi, >>>> >>>> Am Montag, den 27.06.2016, 09:38 +0200 schrieb Corentin Dupont: >>>> > I need it for the game Nomyx, but couldn't find the features I wanted >>>> > from the existing libraries. >>>> >>>> any chance to extend existing libraries to support what you need? >>>> Library proliferation does not really help the ecosystem. >>>> >>>> Greetings, >>>> Joachim >>>> -- >>>> >>>> Joachim “nomeata” Breitner >>>> mail(a)joachim-breitner.de • https://www.joachim-breitner.de/ >>>> XMPP: nomeata(a)joachim-breitner.de • OpenPGP-Key: 0xF0FBF51F >>>> Debian Developer: nomeata(a)debian.org >>>> _______________________________________________ >>>> 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. >> >>

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Fwd: Delivery Status Notification (Failure)
by A Smith 29 Jun '16

29 Jun '16

Hi I'm a Haskell noob, and decided to experiment with a simple package to get me started; ansi-terminal. However, I found a bug in one of the functions. How and to whom do I send a bug report ? Andrew in Scotland

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Using streams to clarify (?) the signature of Data.Text.replace
by Daniel Díaz 29 Jun '16

29 Jun '16

In the "text" package, the signature of Data.Text.replace <http://hackage.haskell.org/package/text-1.2.2.1/docs/Data-Text.html#v:repla…> always sends me looking into the haddocks: replace :: Text -> Text -> Text -> Text Which argument is the text to replace, which is the replacement and which is the text that should be scanned? Imagine a generalized version of replace that 1) works on streams, and 2) allows replacing a sequence of texts (like, say, chapter headers) instead of replacing the same text repeatedly. It could have the following signature: replace' :: Stream (Stream (Of Text) m) m () > -> Stream (Stream (Of Text) m) m Void > -> Stream (Of Text) m r > -> Stream (Of Text) m r Do you find easy to intuit, just by looking at that signature, which is the function of each argument?

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Help to choose a library name
by Corentin Dupont 28 Jun '16

28 Jun '16

Hi community, I'm writing a reactive programming library (yet another). I need it for the game Nomyx, but couldn't find the features I wanted from the existing libraries. Now the library is called Nomyx-Events. But I'd like to find a cool name that is not related to Nomyx... Some propositions: - Nomev - Noa Some French names: - Imprevu (French for unforseen, like in "unforseen event"). - Rendez-vous - Dejavu I like a lot Imprevu. How does it sound to English native speakers? Thanks

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Instances for (->) a (b :: * -> *)?
by Oleg 28 Jun '16

28 Jun '16

Jim Pryor wrote: > If one wants to declare instances for a type schema `a -> _`, one writes > something like this: > instance Context => Class parameters ... ((->) a) where { ... } > But what if you want to declare instances for a type schema `a -> b _`, > that is, where the slot to be filled is not just the result of (->) a, > but rather the composition of that together with another type operation > b :: * -> *? Then one defines a new type: newtype TwoArrow a b x = TwoArrow{unTA:: a -> b -> x} instance MyClass (TwoArrow a b) where ... Ditto for the composition. Alas, one is stuck with adding the dummy conversions TwoArrow/unTA at various places. > Concretely, here's what I'm trying to achieve. I wrote a typeclass for > MonadReaders that are embedded inside (one level) of other MonadReaders, > like this: > {-# LANGUAGE FunctionalDependencies FlexibleInstances > UndecidableInstances #-} > class MonadReader w m => DeepMonadReader w r m | m -> r where > { deepask :: m r > ; deepask = deepreader id The first instance of the curly-braces notation on this list in more than a decade! I think you are trying to build a monad with several pieces of environment. Assuming that just making a record with two different pieces (and making that record the single environment) doesn't work for you, you can find many solutions on Hackage. For example, various extensible effects libraries offer the desired functionality right out of the box. Or, if you really want to define a new class, why not to do something more general, like class Monad m => MonadMReader var r m | var m -> r where ask :: var -> m r to be used like data Var1 = Var1; data Var2 = Var2 do x <- ask Var1 y <- ask Var2 return $ x + y (and implement it, that is, define the instance any way you wish, e.g., with a Free or a Freer monad). For completeness, the old `reflection' trick, see https://hackage.haskell.org/package/reflection offers multiple pieces of configuration data.

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International summer school on metaprogramming (Cambridge, 8-12 Aug 2016)
by Jeremy Yallop 28 Jun '16

28 Jun '16

==================================================================== International summer school on metaprogramming Robinson College, Cambridge, United Kingdom 8th-12th August, 2016 http://www.cl.cam.ac.uk/events/metaprog2016/ ==================================================================== Metaprogramming is an approach to improving programs by treating program fragments (such as expressions or types) as values that the program can manipulate. Metaprogramming comes in various forms, including * staged programming: treating expressions as program values. The execution of a staged program is spread over several phases, with each stage using the available data to generate specialized code. Staged programming has a wide variety of applications — numeric computations, parsing, database queries, generic programming, domain specific languages, and many more. Precompiling the staged code can have dramatic performance improvements, in some cases an order of magnitude or more. * generic programming: treating types as program values. Generic programming can improve code flexibility, allowing to give a single definition of a function that operates in a predictable (but not uniform) way on many different types. Generic programming techniques can be used to define a wide variety of functions, including traversals, comparisons, pretty printers, serialization functions, and many more. The goal of the summer school is to explore the state-of-the art in metaprogramming and its applications, covering both theory and practice. -------------------------------------------------------------------- Lecturers and courses Philip Wadler, Sam Lindley and Shayan Najd (University of Edinburgh) Normalisation and embedding Simon Peyton Jones (Microsoft Research) Oleg Kiselyov (Tohoku University) Type-safe embedding and optimizing domain-specific languages in the typed final style Laurence Tratt (Kings College London) The highs and lows of macros in a modern language Jeremy Yallop (University of Cambridge) Staging generic programming Martin Berger (University of Sussex) Foundations of meta-programming José Pedro Magalhães (Standard Chartered) -------------------------------------------------------------------- Prerequisites The school is aimed at graduate students in programming languages and related areas, but is open to researchers, practitioners and strong masters students with the support of a supervisor. Some experience of typed functional programming in Haskell, OCaml, Scala, or a similar language will be assumed. -------------------------------------------------------------------- Costs Thanks to generous industrial sponsorship, we are able to offer places with significantly reduced fees. There are three categories of fees, all of which cover registration, accommodation in Robinson College from Monday to Friday, and all meals and refreshments. Participants who can pay the full fees will help allocate more fully-subsidised slots to less financially-able students. Your category of fees will not have any direct bearing on your acceptance into the school, but could affect how many slots we can offer. * The full fee is £800. * The standard (partly-subsidised) fee is £295. * We also have a limited number of fully-subsidised places available for a nominal registration fee of £50. We will notify you of your fee upon acceptance. -------------------------------------------------------------------- Application procedure You will need to complete the online registration form at: http://www.cl.cam.ac.uk/events/metaprog2016/application.html and ensure your referees send your references to: metaprog-2016(a)cl.cam.ac.uk by the application deadline. TIMETABLE * 30 June: Application and reference letters deadline. * 10 July: Notification of acceptance. * 24 July: Registration deadline. * 8 August: Summer school. -------------------------------------------------------------------- Further information For questions relating to the material of the school, please contact Jeremy Yallop (jeremy.yallop(a)cl.cam.ac.uk) Ohad Kammar (ohad.kammar(a)cs.ox.ac.uk) For administrative questions, please contact Gemma Gordon (gg417(a)cl.cam.ac.uk)

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Haskell contract position in US (TX)
by Dave Carlson 28 Jun '16

28 Jun '16

I have a client located in the US, Texas who is looking for a Haskell developer ideally with 8+/- years of development experience. If someone is interested in the position below please contact me ASAP. Thanks- Dave Location: TX (potential for some remote/ off-site work) Duration: 6+ months Position Title: Haskell Developer Duties: Client is looking for a Sr. level Haskell developer who has recent experience to work on an AI platform for their product team. Candidate will be assisting building the infrastructure and writing in Haskell coding. Candidate will need to come in from a mentor stand-point and help mentor and train/build- out of platform. Candidate needs to have functional programming experience and be able to do an implementation stack that is based on Haskell & Haskell programming. Candidate needs to be familiar with ECO system tools within Haskell. Candidate needs to have some experience with basic micro services in Haskell & have some Big Data process experience and know how to move data through a pipeline. Candidate needs to understand best practices and bring in the right tools to get the problem done. Necessary Experience: 8+ years of recent Haskell Experience (coding experience & build out) Experience with Functional Programming Able to do implementation stack Exp. with ECO system tools within Haskell Exp. with Basic Micro Services in Haskell Exp. with Big Data process & how to move data through Pipeline Understanding best practices and bring in right tools to get the problem done Desired Experience: Scala Experience GO experience F# Experience Ocamel Language __________________________________ Dave Carlson Senior Recruiting Executive, Software & Hardware Oxford International 100 Cummings Center Suite 365G Beverly, MA 01915 877.258.9982 Office 978.717.7659 Direct david_carlson(a)oxfordcorp.com<mailto:david_carlson@oxfordcorp.com> NYSE: ASGN oxfordcorp.com<http://www.oxfordcorp.com> | LinkedIn<https://www.linkedin.com/company/oxfordinternational> | facebook<https://www.facebook.com/OxfordOGR> | twitter<https://twitter.com/oxfordindex> | Oxford Index Blog<http://info.oxfordcorp.com/oxfordindexblog> The Right Talent. Right Now. The information transmitted, including attachments, is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon this information by persons or entities other than the intended recipient is prohibited. If you received this e-mail in error, please notify the sender immediately by replying to the message and deleting the material from your computer.

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Extensionality in category theory RE: User Requirements Survey for CT Software (Beta)
by Carter Schonwald 27 Jun '16

27 Jun '16

Hey Joie, I'll cc the list because certain list members (Dan, Gershom, and others) can better clarify / expound on this topic Probably the simplest example is function extensionality , that is the reasoning principle that if forall X , g X == f X , then g == f My understanding is that it can be derived in a homotopy type theory setting, but in in more standard type theories like vanilla coq / Agda / lean that folks often use to model certain categorical objects, this is at best a not computable axiom. The very definitions of an epimorphism and monomorphism (the categorical generalization of the dual pair of surjective and injective mappings) Have a sort of function extensional equality! https://ncatlab.org/nlab/show/equality Touches a wee bit On the topic of equalities. There's a number of approaches to treating / deciding when two ... Things (a very technical term 😉)are the same / equal. -Carter _____________________________ From: Breiner, Spencer J. (Fed) <spencer.breiner(a)nist.gov> Sent: Monday, June 27, 2016 9:44 AM Subject: RE: [Haskell-cafe] User Requirements Survey for CT Software (Beta) To: Carter Schonwald <carter.schonwald(a)gmail.com>, Murphy, Joie R. (Assoc) <joie.murphy(a)nist.gov> Cc: Subrahmanian, Eswaran (Assoc) <eswaran.subrahmanian(a)nist.gov> Carter, Thanks for your reply. I removed the Haskell mailing list from the cc because I don’t know the list’s etiquette, but please forward this response back to the list if you are aiming for a public discussion. I’m not quite sure what you mean by “extensional elements”? Is this extension in the sense of “one class extends another” (in which case this would be expressed explicitly by functors). Or extension in the (related) sense of “the extension of a proposition”, the elements which satisfy it. These sorts of issues would probably be expressed as functors into (some computational implementation of) finite sets. Let me know and I’m happy to talk some more. Thanks again, Spencer Breiner NIST From: Carter Schonwald [mailto:carter.schonwald@gmail.com] Sent: Friday, June 24, 2016 8:35 PM To: Murphy, Joie R. (Assoc) <joie.murphy(a)nist.gov> Cc: haskell-cafe(a)haskell.org; Subrahmanian, Eswaran (Assoc) <eswaran.subrahmanian(a)nist.gov>; Breiner, Spencer J. (Fed) <spencer.breiner(a)nist.gov> Subject: Re: [Haskell-cafe] User Requirements Survey for CT Software (Beta) How do you plan to handle extensional elements of category theory? On Friday, June 24, 2016, Murphy, Joie R. (Assoc) <joie.murphy(a)nist.gov> wrote: Hello, My name is Joie Murphy and I am a Summer Research Student at the US National Institute of Standards and Technology (NIST), working with Drs. Spencer Breiner and Eswaran Subrahmanian. We are currently gathering user requirements for category theoretic software to be developed by or with NIST in the future. This questionnaire will give us insight about your past or present use of CT software and your ideal uses for such software. Providing us with the information on how you would like to use this type of software will help us to make the right design choices in development. The survey is available on Google Forms:http://goo.gl/forms/vfOgR26dHnKynHU23 If you have any colleagues who might be willing to fill out this survey, you can forward our message or you can provide us with their contact information at the end of the survey. If you have any questions or concerns, please feel free to contact us by replying to this email. We would like to thank you for your participation in this initial step of the development process. Regards, Joie Murphy

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Re: [Haskell-cafe] [Haskell] The Haddock documentation is not showing up on the Hackage
by Henning Thielemann 27 Jun '16

27 Jun '16

On Mon, 27 Jun 2016, KwangYul Seo wrote: > I uploaded a package named enchant on the Hackage last week, but the > Haddock documentation is not showing up yet. The Status field says "Docs > pending" and "Build status unknown". This is certainly not for haskell(a)haskell.org. I am answering to haskell-cafe and cabal-devel. > https://hackage.haskell.org/package/enchant-0.1.0.0 > > enchant uses c2hs as a build tool to generate the FFI binding and > requires libenchant-dev to be installed on the machine. I wonder how I > can tell these build requirements to the Hackage server. I assume that it is not a good idea to install many additional packages on the Haskell server. Thus I think the best you can do is to upload the documentation yourself via the package maintenance site. Here is a script that should help creating the docs locally and upload them to Hackage: https://raw.githubusercontent.com/ekmett/lens/master/scripts/hackage-docs.sh

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