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Applicative & Monad as interaction between categories

haskell-cafe - Tue, 08/05/2014 - 9:46am
Hi all, I recently came across of two blog posts[1][2] by Gabriel Gonzales where he shows motivation for writing compositional functions -- and thus why the concept of category is useful -- and motivation to write functors between them. I wanted to know if something similar for has been done to `Applicative' and `Monad' as design pattern and interaction between categories. I've searching but I always hit the Monad tutorials and more info on how to use them. Thanks in advance. Excuse my English. [1]: http://www.haskellforall.com/2012/08/the-category-design-pattern.html [2]: http://www.haskellforall.com/2012/09/the-functor-design-pattern.html
Categories: Offsite Discussion

Building network without MSYS [Was: Splitting Network.URI from the network package]

libraries list - Mon, 08/04/2014 - 9:52pm
Hello. I consider the original proposal to be well founded and I support it. However, I started to think if there is anything we can improve about installation of network package itself? Maybe we can get rid of MSYS, at least for the end users of network package? How would that happen? The following plan came to my mind: 1. Select a single supported configuration (Windows version) 2. Execute a "normal" build with MSYS 3. Extract a configuration that was "discovered" by MSYS 4. Bake in the configuration into installation files to be used on Windows when MSYS is not present. There shouldn't be that many supported configurations on Windows. I think it is reasonable to do: 1. Windows XP 2. Windows 7 3. Windows 8 4. some Windows Server versions? For each system the variants would be: 1. 32-bit system, 32-bit GHC 2. 64-bit system, 32-bit GHC 3. 64-bit system, 64-bit GHC Right now I have done the procedure above for my own 64-bit Windows 7/32-bit GHC pair. I also added some simple logic of choosing between "Sim
Categories: Offsite Discussion

[ANN] StrappedTemplates - general purpose templates

haskell-cafe - Mon, 08/04/2014 - 6:40pm
Hello all, I found that I wasn't quite satisfied by the template offerings (Heist, Hastache, Shakespearean, etc..) of Haskell, so I built my own. The goal is to have simple syntax that non-haskellers would be comfortable using, resembles templates found in other languages (Jinja, Django, etc) and an interface to render them that I don't have to think very hard to use. Features include inheritance, logic, includes, functions, and relatively speedy rendering (much faster than interpreted templates like Heist-I and Hastache) . Its very much a work in progress, but I felt that it was enough for an initial release and get general feedback on it. Comments are appreciated. One thing that I want to improve is how functions are handled in the template and in the "InputBucket", extend the syntax to allow you to do more inside the template and be able to define your own block functions. These will probably be added next major release. http://hackage.haskell.org/package/StrappedTemplates https://github.com/hansonk
Categories: Offsite Discussion

New Functional Programming Job Opportunities

haskell-cafe - Mon, 08/04/2014 - 5:00pm
Here are some functional programming job opportunities that were posted recently: Pragmatic Haskell Developer at Anchor Systems http://functionaljobs.com/jobs/8729-pragmatic-haskell-developer-at-anchor-systems Cheers, Sean Murphy FunctionalJobs.com
Categories: Offsite Discussion

"Standardising" Haskell AST for tooling

haskell-cafe - Sun, 08/03/2014 - 8:27pm
Hi all I am looking at updating HaRe for GHC 7.8.3, and I am fighting my way through the AST changes. One of the things I have had at the back of my mind for a while is to use something like Kure universes or more generally lens to provide a set of isomorphisms from the various flavours of AST into some kind of standardised internal representation, allowing easier tool manipulation. This could potentially decouple the tools from the specific compiler/analyzer, so they could work across GHC 7.6.x, GHC 7.8.x, haskell-src-exts, haste, etc.. Obviously there would be limitations to this where an advance in the language brings in new features, but a lot of useful tool work can be done that does not touch the new stuff. I don't know if anything similar is planned in either ghc-server or another toolchain. My haskell-token-utils is a first limited attempt to bring source code round tripping to a variety of backends, but a more general solution to the AST phase would help tooling in general So, is this worth d
Categories: Offsite Discussion

[ANN] Hayoo Relaunch

haskell-cafe - Sun, 08/03/2014 - 2:13pm
Hi Cafe, Hayoo <http://hayoo.fh-wedel.de> has been relaunched. Hayoo is a search engine for Hackage packages, which allows you to search for functions, data types and packages. It is currently work in progress. Any feedback is greatly appreciated! Hayoo uses Hunt <https://github.com/hunt-framework> for indexing and searching, which is the successor of Holumbus. Hunt is a flexible, lightweight search platform with a powerful query language and JSON API. Example search requests are: * Function names: map <http://hayoo.fh-wedel.de/?query=map> * Function signatures: (a->b)->f a->f b <http://hayoo.fh-wedel.de/?query=%28a-%3Eb%29-%3Ef+a-%3Ef+b> * Module names: Control.Loop <http://hayoo.fh-wedel.de/?query=Control.Loop> Have a look at the examples on <http://hayoo.fh-wedel.de/examples> for some advances queries. The old Hayoo and Holumbus are still online at <http://holumbus-alt.fh-wedel.de/>
Categories: Offsite Discussion

http://www.downforeveryoneorjustme.com/haskell.org

haskell-cafe - Sun, 08/03/2014 - 1:52pm
Thinks always break on the weekend, don’t they! Apologies if this is a scheduled outtake. In the meantime, there’s fortunately a Haddock mirror on http://haddocks.fpcomplete.com/fp/7.7/20131212-1/ ;-) Cheers, Tim
Categories: Offsite Discussion

Haskell Platform 2014.2.0.0 Release Candidate 4(Windows only)

haskell-cafe - Sun, 08/03/2014 - 4:00am
This is an update to the Windows RC2 candidates. These candidates fix three problems with the installation scripts. The binary build of the packages has not changed. *Fixes:* - Fix the PATH to add the location where binaries are installed with "cabal install --global" - Fix the url shortcut that is installed, to point to the platform+ghc master indices, rather than just the ghc indices - Fix where a 32-bit HP installed on a 64-bit system was going *Installers can be found here:* - HaskellPlatform-2014.2.0.0-i386-RC4-setup.exe <http://www.ozonehouse.com/mark/platform/HaskellPlatform-2014.2.0.0-i386-RC4-setup.exe> - HaskellPlatform-2014.2.0.0-x86_64-RC4-setup.exe <http://www.ozonehouse.com/mark/platform/HaskellPlatform-2014.2.0.0-x86_64-RC4-setup.exe> - Mark P.S.: You might have noticed that the server that hosted the RC files was down intermittently yesterday and today. It suffered a double (!) disk failure. It is back up with shiny new disks. P.P.S: As always, for the reason
Categories: Offsite Discussion

typed tagless-final interpretation examples brokenwith recent ghc

haskell-cafe - Sat, 08/02/2014 - 4:28pm
Hi all, I've been reading up on typed tagless-final interpretations [1] and the accompanying examples. It seems the stuff about CPS transformations does no longer compile, probably because of stricter typing rules. I tried both ghc 7.6 and ghc 7.8, which both give a different kind of error message. It's a bit much and long to paste here though. I would really like to get the example working, but couldn't manage by only supplying type signatures. Perhaps there is some language pragma I can turn on or off to get the old behaviour back? The 2 files needed (no further libraries needed) are: - http://okmij.org/ftp/tagless-final/course/TTF.hs (working) - http://okmij.org/ftp/tagless-final/course/CPS.hs (problem) All help would be greatly appreciated. Regards, Mathijs [1] http://okmij.org/ftp/tagless-final/course/index.html
Categories: Offsite Discussion

re-reading a Samson Abramsky paper ..

haskell-cafe - Sat, 08/02/2014 - 8:29am
http://staff.science.uva.nl/~ssimon/indjournal/pdf/abramsky.pdf .. no words .. I will let Samson speak for himself .. :-) Hopefully my audience cam keep up with Abramsky's terseness .. he is very "cheeky" ...
Categories: Offsite Discussion

Functional programming and William Lawvere's notion of "variable sets"(vs topos of "static sets") in a Topos ...

haskell-cafe - Sat, 08/02/2014 - 7:28am
Hello Haskellers, I have been re-reading William Lawvere's description of "variable sets" (a functor category) in "a elementary topoi" on a discrete poset/preset vs a "abstract sets" in the topos of abstract sets . In Haskell( and other FPLs .. ) aren't "pure" computations just over the topos of abstract sets and "mutable" /"time-varying/stateful" computations aren't just "variable sets" (i.e. a functor over a discrete preset-poset)?? Please forgive my bad English :-( If uncertain aboyt my Englsih, please say so. Kind regards, Vasya P.S. Yes I am familiar with Eugenio Moggi's papers on using monads for stateful computations ..
Categories: Offsite Discussion

Proposal: add unfoldr1 to the somewhere in base

libraries list - Sat, 08/02/2014 - 12:21am
Way back in 2001, Shin-Cheng Mu proposed an unfoldr1 combinator: http://code.haskell.org/~dons/haskell-1990-2000/msg06775.html I discussed this a bit with shachaf in #haskell, and he noted that a similar function, with a slightly different but isomorphic type, appears in Edward Kmett's semigroups package as the unfoldr for NonEmpty. I propose that we add this. It can be written unfoldr1 :: (b -> (a, Maybe b)) -> b -> [a] unfoldr1 f b = go b where go b = case f b of (a, may_b) -> a : maybe [] go may_b With the appropriate RULES, it can be wrapped up in build and fuse properly. I'd love to see this written as an unfoldr instead. Does anyone know if that's possible?
Categories: Offsite Discussion

ICFP 2014 Final Call for Participation

haskell-cafe - Fri, 08/01/2014 - 10:51pm
[ Early registration ends 3 Aug; Invited speakers and conference program have been announced. ] ===================================================================== Final Call for Participation ICFP 2014 19th ACM SIGPLAN International Conference on Functional Programming and affiliated events August 31 - September 6, 2014 Gothenburg, Swedenhttp://icfpconference.org/icfp2014/ ===================================================================== ICFP provides a forum for researchers and developers to hear about the latest work on the design, implementations, principles, and uses of functional programming. The conference covers the entire spectrum of work, from practice to theory, including its peripheries. A full week dedicated to functional programming: 1 conference, 1 symposium, 10 workshops, tutorials, programming contest results, student research competition * Program: http://icfpconference.org/icfp2014/program.html * Accepted Papers: http://icfpconference.org/icfp2014/accepted.html *
Categories: Offsite Discussion

ICFP 2014 Final Call for Participation

General haskell list - Fri, 08/01/2014 - 10:50pm
[ Early registration ends 3 Aug; Invited speakers and conference program have been announced. ] ===================================================================== Final Call for Participation ICFP 2014 19th ACM SIGPLAN International Conference on Functional Programming and affiliated events August 31 - September 6, 2014 Gothenburg, Swedenhttp://icfpconference.org/icfp2014/ ===================================================================== ICFP provides a forum for researchers and developers to hear about the latest work on the design, implementations, principles, and uses of functional programming. The conference covers the entire spectrum of work, from practice to theory, including its peripheries. A full week dedicated to functional programming: 1 conference, 1 symposium, 10 workshops, tutorials, programming contest results, student research competition * Program: http://icfpconference.org/icfp2014/program.html * Accepted Papers: http://icfpconference.org/icfp2014/accepted.html *
Categories: Incoming News

EsseOS: Haskell-based tailored services for the cloud

haskell-cafe - Fri, 08/01/2014 - 6:14pm
Hi, I came across this seemingly interesting paper: EsseOS: Haskell-based tailored services for the cloud http://dl.acm.org/citation.cfm?id=2541587 which is unfortunately behind a paywall. I was wondering if someone knew about a freely accessible version of that paper, or about some project page, or just heard of it. Thank you, Thu
Categories: Offsite Discussion

haskell on Debian

haskell-cafe - Fri, 08/01/2014 - 4:43pm
I want to reinstall Haskell on Debian (in Virtualbox on Windows). So: apt-get remove haskell-platform Deleted all maps with packages in it. apt-get install haskell-platform (installing previous selected ... etc) cabal update All this without errors of warnings. cabal install cabal-install Error: /var/lib/ghc/package.conf.d: openFile: does not exist Why this error? Setup doesn't create this directory? _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe< at >haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Categories: Offsite Discussion

Splitting Network.URI from the network package

libraries list - Fri, 08/01/2014 - 12:31pm
This was brought up last year[1], and I'd like to bring it up again, based on a recent issue I was working through with a user[2]. I realize that this is a breaking change, but: 1. It's a minor breaking change: you simply need to add an extra package to your build-depends. 2. The problems caused by having a parsec dependency in network can be severe, especially for new users (I'll describe the details after the proposal). Concretely, I believe we should do the following: 1. Create a new package, network-uri, version 2.5.0.0, which exposes no modules and has an upper bound `network < 2.6. 2. Create a second release of network-uri, version 3.0.0.0, which provides the Network.URI module verbatim as provided by the network package today, and has a lower bound `network >= 3.0`. 3. Release network version 3.0.0.0, with no changes from the currently released version, except that (a) no Network.URI module is provided, and (b) there is no parsec dependency. I don't remember how the discussion went last time, but
Categories: Offsite Discussion

Does web-based email harm mailman lists?

haskell-cafe - Fri, 08/01/2014 - 10:46am
Beautiful haskell people, Ever noticed the lacunae on some list threads? Someone hits reply and instead of reflecting via mailman, it goes direct to OP. OP notices absence of To:haskell-cafe and adds it back in in their reply to the reply. End result? The thread looks like OP having a convo with themselves. Unless you look at the quoted parts, which you have to click to reveal in web-based email. The convention, say with a google-groups based mailing list, is that conversations in mailing list are public by default. With some manual C&P, you can email responses in private. For cafe participants using web-based email, the situation is reversed, through no fault of their own. Approx 18 months ago, the haskell-beginners list suffered the same problem [1]. After some digging, it looks like there's a configurable option to Do The Right Thing: http://ccit.mines.edu/Mailman-FAQ#25 I was also privately emailed that there are downsides I wasn't aware of: Reply-To Munging Considered Harmful http://www.unicom.
Categories: Offsite Discussion

Tor project and Haskell (FPL) ,..

haskell-cafe - Fri, 08/01/2014 - 7:58am
I wasn't trying to offend anybody .... Only trying to provoke a lively discussion in order lift all boats. Sometimes one sentence IHMO provokes thought. In any case I appreciate all responders :-) Kind thanks friends. Vasya _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe< at >haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Categories: Offsite Discussion

Haskell Platform 2014.2.0.0 Release Candidate 3

haskell-cafe - Thu, 07/31/2014 - 9:48pm
Small update to the Haskell Platfrom 2014.2.0.0 release: We have new Release Candidate 3 versions of the source tarball... and a new generic-linux bindist of the platform! - source tarball: haskell-platform-2014.2.0.0-srcdist-RC3.tar.gz <http://www.ozonehouse.com/mark/platform/haskell-platform-2014.2.0.0-srcdist-RC3.tar.gz> - generic linux: haskell-platform-2014.2.0.0-unknown-linux-x86_64-RC3.tar.gz <http://www.ozonehouse.com/mark/platform/haskell-platform-2014.2.0.0-unknown-linux-x86_64-RC3.tar.gz> *Windows and OS X users: There are no RC3 versions - as the RC2 versions seem to be holding up fine!* *General* - hptool (and hence ./platform.sh script) take a new --prefix parameter that is used for generic (non-OS X, non-Windows) builds: It sets the root under which haskell installations are located. Defaults to /usr/local/haskell. Everything will be placed in a directory named ghc-7.8.3-<arch> under this prefix. - activate-hs script for default Posix-like builds - sma
Categories: Offsite Discussion