January 2016 - Haskell-Cafe

Host-Oriented Template Haskell
by Ericson, John 19 Jan '16

19 Jan '16

As is well known, TH and cross-compiling do not get along. There are various proposals on how to make this interaction less annoying, and I am not against them. But as I see it, the problem is largely inherent to the design of TH itself: since values can (usually) be lifted from compile-time to run-time, and normal definitions from upstream modules to downstream modules' TH, TH and normal code must "live in the same world". Now this restriction in turn bequeaths TH with much expressive power, and I wouldn't advocate getting rid of it. But many tasks do not need it, and in some cases, say in bootstrapping compilers[1] themselves, it is impossible to use TH because of it, even were all the current proposals implemented. For these reason, I propose a new TH variant which has much harsher phase separation. Normal definitions from upstream modules can not be used, lifting values is either not permitted or is allowed to fail (because of missing/incompatible definitions), and IO is defined to match the behavior of the host, not target, platform (in the cross compiling case). The only interaction between the two phases is that quoted syntax is resolved against the the run-time phase's definitions (just like today). Some of you may find this a shoddy substitute for defining a subset of Haskell which behaves identically on all platforms, and optionally constraining TH to it. But the big feature that my proposal offers and that one doesn't is to be able to independently specify compile-time dependencies for the host-oriented TH---this is analogous to the newish `Setup.hs` dependencies. That in turns leads to what I think is the "killer app" for Host-Oriented TH: exposing the various prepossessors we use (alex, happy, hsc2hs, even CPP) into libraries, and side-stepping any need for "executable dependencies" in Cabal. Note also that at least hsc2hs additionally requires host-IO---there may not even exist a C compiler on the target platform at all. Finally, forgive me if this has been brought up before. I've been thinking about this a while, and did a final pass over the GHC wiki to make sure it wasn't already proposed, but I could have missed something (this is also my first post to the list). John [1]: https://github.com/ghcjs/ghcjs/blob/master/lib/ghcjs-prim/GHCJS/Prim/Intern…

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Re: [Haskell-cafe] [ANNOUNCE] Haskell DBMS: Project:M36
by A.M. 18 Jan '16

18 Jan '16

On 12/21/2015 11:30 AM, Rémi Vion wrote: > Hello, Project:M36 seems amazing, thanks ! > Thank your also for the link to the "/Out of the Tar Pit" paper/ > (http://shaffner.us/cs/papers/tarpit.pdf > <http://shaffner.us/cs/papers/tarpit.pdf>). Thank you Remi. We are working on completing the final components described in precisely this paper. Then, we will publish an essay about how Project:M36 meets the paper's requirements for functional-relational programming. > > Are you aware of people using Project:M36 in production ? The project is very young and unlikely to be used in production. Currently, I would recommend it to users interested in learning about the mathematics behind the relational algebra. In comparison, SQL is a terrible platform for learning about the relational algebra because SQL made some poor historical decisions. Here is an essay on one facet of this argument: https://github.com/agentm/project-m36/blob/master/docs/on_null.markdown > Is there some user feedback available somewhere ? Please use the github issue system if you encounter any problems. Or are you asking for a "frequently-asked questions" section? We should certainly add that. > For small scale applications, do you think M36 is ready enough to be a > viable alternative to Postgres ? Project:M36 would be a viable replacement for PostgreSQL for experimental use only. There are many more optimizations at every level which need to be implemented before Project:M36 is on-par with PostgreSQL and we are working on many new features. Project:M36 has also not yet achieved feature parity with PostgreSQL, though Project:M36 already includes some features impossible in PostgreSQL (such as nested relations). Thanks for trying Project:M36! Any feedback you have would be very valuable. Cheers, M

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Stackage is reverting to aeson-0.9
by Dan Burton 18 Jan '16

18 Jan '16

This means that LTS 4 is being discontinued, and LTS 5 is imminent. See the announcement blog post: https://unknownparallel.wordpress.com/2016/01/18/stackage-is-reverting-to-a… See also related discussion (yesterday): https://www.reddit.com/r/haskell/comments/41gpdk/lts4_with_aeson010_is_bein… If there are any questions or concerns, don't hesitate to ping me. -- Dan Burton

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Haskell dev roles with Strats at Standard Chartered
by Don Stewart 18 Jan '16

18 Jan '16

Hi folks, I'm hiring 3 more devs to write Haskell for Standard Chartered in London and Singapore. Details of the roles below, but broadly in FX algo pricing and pricing automation. Ability to write "tight" total Haskell that can run 24/7 and do the right thing is needed. https://donsbot.wordpress.com/2016/01/18/haskell-developer-roles-at-standar… CVs to me at Standard Chartered -- Don

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project compile with multi-versions of alex
by Zilin Chen 18 Jan '16

18 Jan '16

Hi Cafe, I have a Haskell project which has ~90 dependencies (transitively) and is managed with plain cabal (w/o stackage, etc.). I try to keep it compile with a few latest releases of GHC (so right now 7.8.4, 7.10.1, 7.10.2 and 7.10.3). It was tractable with conditionals in the cabal config file with minor annoyance. But recently I found this issue:language-c-quote-0.11.3 does not compile with alex 3.1.5 [1]. I was wondering if I should also allow a few versions of executables, like alex, happy, etc (I can see though it will be a huge pain); or should I force all users to use the latest versions of them (I don't know if they are compatible with old ghc versions)? What's the common practice for other projects? Any hints? What should I write in my cabal config? Thanks, Zilin [1]https://github.com/mainland/language-c-quote/issues/57

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ANN: stack-1.0.2
by Emanuel Borsboom 17 Jan '16

17 Jan '16

New version released of Stack, a build tool. See haskellstack.org for installation and upgrade instructions. Release notes: - Arch Linux: Stack has been adopted into the official community repository <https://www.archlinux.org/packages/community/x86_64/stack/>, so we will no longer be updating the AUR with new versions. See the install/upgrade guide <http://docs.haskellstack.org/en/stable/install_and_upgrade.html#arch-linux> for current download instructions. Major changes: - stack init and solver overhaul #1583 <https://github.com/commercialhaskell/stack/pull/1583> Other enhancements: - Disable locale/codepage hacks when GHC >=7.10.3 #1552 <https://github.com/commercialhaskell/stack/issues/1552> - Specify multiple images to build for stack image container docs <http://docs.haskellstack.org/en/v1.0.2/yaml_configuration.html#image> - Specify which executables to include in images for stack image container docs <http://docs.haskellstack.org/en/v1.0.2/yaml_configuration.html#image> - Docker: pass supplemantary groups and umask into container - If git fetch fails wipe the directory and try again from scratch #1418 <https://github.com/commercialhaskell/stack/issues/1418> - Warn if newly installed executables won’t be available on the PATH #1362 <https://github.com/commercialhaskell/stack/issues/1362> - stack.yaml: for stack image container, specify multiple images to generate, and which executables should be added to those images - GHCI: add interactive Main selection #1068 <https://github.com/commercialhaskell/stack/issues/1068> - Care less about the particular name of a GHCJS sdist folder #1622 <https://github.com/commercialhaskell/stack/issues/1622> - Unified Enable/disable help messaging #1613 <https://github.com/commercialhaskell/stack/issues/1613> Bug fixes: - Don’t share precompiled packages between GHC/platform variants and Docker #1551 <https://github.com/commercialhaskell/stack/issues/1551> - Properly redownload corrupted downloads with the correct file size. Mailing list discussion <https://groups.google.com/d/msg/haskell-stack/iVGDG5OHYxs/FjUrR5JsDQAJ> - Gracefully handle invalid paths in error/warning messages #1561 <https://github.com/commercialhaskell/stack/issues/1561> - Nix: select the correct GHC version corresponding to the snapshot even when an abstract resolver is passed via --resolver on the command-line. #1641 <https://github.com/commercialhaskell/stack/issues/1641> - Fix: Stack does not allow using an external package from ghci #1557 <https://github.com/commercialhaskell/stack/issues/1557> - Disable ambiguous global ‘—resolver’ option for ‘stack init’ #1531 <https://github.com/commercialhaskell/stack/issues/1531> - Obey --no-nix flag - Fix: GHCJS Execute.hs: Non-exhaustive patterns in lambda #1591 <https://github.com/commercialhaskell/stack/issues/1591> - Send file-watch and sticky logger messages to stderr #1302 <https://github.com/commercialhaskell/stack/issues/1302> #1635 <https://github.com/commercialhaskell/stack/issues/1635> - Use globaldb path for querying Cabal version #1647 <https://github.com/commercialhaskell/stack/issues/1647>

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Haskell Weekly News
by Kim-Ee Yeoh 15 Jan '16

15 Jan '16

*Top Picks:* - Team GHC announces the first release candidate of version 8.0 <http://haskell.1045720.n5.nabble.com/ANNOUNCE-Glasgow-Haskell-Compiler-8-0-…>. New features include: - Strict and StrictData extensions - TypeFamilyDependencies extension for injective type families <https://ghc.haskell.org/trac/ghc/wiki/InjectiveTypeFamilies> - TypeInType extension for more dependent typing hackery - explicit type application in plain Haskell, not Core - Applicative do-notation - a spanking new pattern-match checker - modularization of the ghci interpreter: it can now run as an independent process Note that the announcement includes a list of bugs linked to the new features. - The engineers at an Australian real estate listings website explain how they "used Category Theory to solve a problem in Java." <http://techblog.realestate.com.au/how-we-used-category-theory-to-solve-a-pr…> They face the problem of their search API having grown gnarly and inextensible. First they offer a monoid tutorial culminating in SearchResults -> SearchResults endomorphisms. Then they regularize their database lookups as Kleisli-composable instances of a monomorphic state monad of type (DataSource, SearchResults) -> SearchResults. Finally, they profunctorize the state monad for mereological development of the DataSource. So how was the blog post received? A vocal section of the HN community express skepticism <https://news.ycombinator.com/item?id=10892696>. One haskell subredditor found it "an excellent article." <https://www.reddit.com/r/haskell/comments/40s85b/how_we_used_category_theor…> - Verity Stob <https://en.wikipedia.org/wiki/Verity_Stob>, the doyen of information technology satire, skewers the cargo culting of Functional Programming <http://www.theregister.co.uk/2016/01/13/stob_remember_the_monoids/> and by the by writes a monad tutorial (omg!). Haskell redditors chuckle and cluck at the hatchet job <https://www.reddit.com/r/haskell/comments/40wqzf/learn_you_func_prog_on_fiv…> . - Team Wander Nauta creates Viskell <https://github.com/wandernauta/viskell>, "an experimental visual programming environment for a typed (Haskell-like) functional programming language." Programming with touch tablets in mind, he implements Viskell in Java 8 because "Haskell lacks suitable GUI libraries, and we need good multi-touch support." A slides PDF contains more screenshots. <https://github.com/wandernauta/viskell/blob/master/viskell-nlfpday.pdf> Well-received on both Hacker News <https://news.ycombinator.com/item?id=10874294> and /r/haskell <https://www.reddit.com/r/haskell/comments/406au9/viskell_visual_programming…> . *Quotes of the Week:* - Tom Ellis: <https://news.ycombinator.com/item?id=10870488#up_10874714> In Haskell you don't fight the type system. It fights your bugs. - Jeremy Bowers: <https://news.ycombinator.com/item?id=10892293#up_10896419> The reason I find Haskell interesting is precisely that it's the only place I know where the theoretically-minded and the practically-minded get together and interpollinate. Everywhere else the one group pretty much just sneers at the other. - Redditor lukewarm: <https://www.reddit.com/r/haskell/comments/40aa4n/how_to_make_industry_quali…> Yes, you can write industry quality software in Haskell. Do all your computations in the IO monad, keep intermediate results in MVars. Use only Int and String types. Use exceptions to handle errors. Write yourself custom constructs to emulate for and while loops, preferably using Template Haskell. -- Kim-Ee

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repa parallelization results
by Anatoly Yakovenko 14 Jan '16

14 Jan '16

https://gist.github.com/aeyakovenko/bf558697a0b3f377f9e8 so i am seeing basically results with N4 that are as good as using sequential computation on my macbook for the matrix multiply algorithm. any idea why? Thanks, Anatoly

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Call for Participation: BOB 2016 (February 19, Berlin)
by Stefan Wehr 14 Jan '16

14 Jan '16

Quick reminder: the early registration deadline for BOB 2016 is this Sunday! We have some interesting Haskell talks and tutorials at BOB 2016! ================================================================ BOB 2016 Conference "What happens if we simply use what's best?" February 19, 2016 Berlin http://bobkonf.de/2016/ Program: http://bobkonf.de/2016/program.html Registration: http://bobkonf.de/2016/registration.html ================================================================ BOB is the conference for developers, architects and decision-makers to explore technologies beyond the mainstream in software development, and to find the best tools available to software developers today. Our goal is for all participants of BOB to return home with new insights that enable them to improve their own software development experiences. The program features 14 talks and 8 tutorials on current topics: http://bobkonf.de/2016/program.html The subject range of talks includes functional programming, advanced front-end development, data management, and sophisticated uses of types. The tutorials feature introductions to Erlang, Haskell, Scala, Isabelle, Purescript, Idris, Akka HTTP, and Specification by Example. Elise Huard will hold the keynote talk - about Languages We Love. Registration is open online: http://bobkonf.de/2016/registration.html NOTE: The early-bird rates expire on January 17, 2016! BOB cooperates with the :clojured conference on the following day. There is a registration discount available for participants of both events. http://www.clojured.de/

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Hiring: Haskell at Biotech Startup!
by Andrew Gibiansky 13 Jan '16

13 Jan '16

Hello haskell-cafe, I'm an engineer at Karius, a "stealth-mode" biotech startup in Menlo Park, CA, and we're looking to hire a few folks to write software (and we use Haskell!). Currently only hiring locally or with relocation (though that could change in the future, so feel free to get in touch regardless!). We are a team of crazy biologists, engineers, data scientists and clinicians on a mission to change forever the way infectious diseases are diagnosed and treated. We face incredibly interesting challenges in software engineering, machine learning and molecular biology, as we push the limits of diagnostics and genomic technologies. We're hiring computational biologists, software engineers and data scientists. If you're a software engineer, we're looking for experience in front-end, back-end, web development, intrastructure, devops, bioinformatics, and machine learning. We have a varied list of challenges; we build large data processing pipelines to analyze data from in-house DNA sequencers, separate the signal from the noise and extract what we need, and visualize this in ways that are helpful for scientists and doctor; we build web apps and tools for biologists and doctors to use to plan, conduct, and analyze experiments; we work closely with molecular biologists to analyze data generated by these experiments and develop novel computational biology methods. Our technology stack, as of right now: - Python (for bioinformatics) - Rails (for one backend codebase in maintenance mode) - React and ES6 (for front-end interfaces) - Haskell (for infrastructure and new development) - Backed by AWS and Docker We just put our first large Haskell application into production and are planning on continuing with Haskell; this is an opportunity to use Haskell at a cutting-edge biotechnology startup. If any of this sounds exciting to you, please don't hesitate to get in touch with us by emailing Greg Stock atgstock(a)kariusdx.com. Take a look at our job postings on AngelList <https://angel.co/karius/jobs> for more detail, though they won't say much about Haskell. You may know me personally from my work with IHaskell <http://github.com/gibiansky/IHaskell> and my hindent style <http://github.com/chrisdone/hindent>; Greg Weber is also here at Karius, whom you may know from his contributions to Persistent <http://github.com/yesodweb/persistent>, Yesod <http://github.com/yesodweb/yesod>, and Shelly <https://github.com/yesodweb/Shelly.hs>. -- Andrew Gibiansky

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