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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 ..
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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

[ANN] hsimport 0.5: configurable pretty printing and placing of imports

haskell-cafe - Thu, 07/31/2014 - 8:59pm
Hi all, hsimport[1] is a command line program for extending the import list of a Haskell source file. There's an integration[2] for the vim editor, which can automatically extend the import list for the symbol under the cursor. hsimport 0.5 changes: - configurable[3] pretty printing of imports - configurable placing of new imports - support of multi line imports - better handling of incomplete/invalid Haskell source files Grettings, Daniel [1] https://github.com/dan-t/hsimport [2] https://github.com/dan-t/vim-hsimport [3] https://github.com/dan-t/hsimport/blob/master/README.md
Categories: Offsite Discussion

Seeking comments on proposed fusion rules

libraries list - Thu, 07/31/2014 - 7:38pm
The rules: lpaste.net/108508 The boring explanation: As I mentioned earlier, we currently can't fuse things like foldr (x : build g) The foldr can't see the build. Earlier, I considered a simple cons/build rule that would rewrite x : build g to build (\c n -> x `c` g c n) I wasn't quite satisfied with this approach, largely because it treats foldr c n (x1 : x2 : ... : xn : build g) one way, and foldr c n ([x1, x2, ..., xn) : build g) another way. The former expands out the foldr, while the latter (via various rules involving augment) translates into a foldr over [x1, x2, ..., xn]. I therefore came up with the idea of translating x1:x2:...:xn:build g into [x1:x2:..:xn]++build g, and then letting the current rules do their thing. dolio and carter (in #ghc) were concerned about what would happen if fusion *didn't* occur, in which case the resulting code appears to be *worse*. So then I wrote some rules to fix that up, which actually look likely to be good rules in general. They turn [x1:x2:...:xn
Categories: Offsite Discussion

Bad interaction of inlinePerformIO and mutablevectors

haskell-cafe - Thu, 07/31/2014 - 11:57am
I'm trying to understand why some code isn't behaving as I'd expect, and to determine whether it's a bug or not (and where that bug might be). Here's the simplest version of the code: import Data.ByteString.Internal (inlinePerformIO) import qualified Data.Vector as V import qualified Data.Vector.Mutable as VM main :: IO () main = do vm <- VM.new 1 VM.write vm 0 'A' let x = inlinePerformIO $ VM.write vm 0 'B' x `seq` (V.freeze vm >>= print) A more complete example is available on lpaste[1]. The problem is that I would expect the output to be "B", but in fact "A" is still printed. From the longer paste that I linked to, you can see that: * When using unsafePerformIO and unsafeDupablePerformIO, the semantics work as I would have expected: "B" is printed after forcing evaluation of the result. * If I add a `VM.read vm 0` call after the write, it also works. * Using IORef, the behavior is also as I would have expected: as soon as the result is evaluated, th
Categories: Offsite Discussion

Newtype derivation understanding problem

haskell-cafe - Thu, 07/31/2014 - 11:55am
Excuse me if the question is silly. Thought this MonadCatchIO will be removed in next version of snap, current version has it and I can't understand this derivation: [0] L.Lensed seems like just a newtype wrapper around a function [1], and there is no instance of MonadCatchIO for a function. How is it derived? [0]: https://github.com/snapframework/snap/blob/0.13.2.8/src/Snap/Snaplet/Internal/Types.hs#L260 [1]: https://github.com/snapframework/snap/blob/0.13.2.8/src/Snap/Snaplet/Internal/Lensed.hs#L20 _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe< at >haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Categories: Offsite Discussion

Tor project

haskell-cafe - Thu, 07/31/2014 - 4:42am
Haskell contributions to http://www.torproject.org .. .any thoughts ??
Categories: Offsite Discussion

Haskell Weekly News: Issue 300

haskell-cafe - Thu, 07/31/2014 - 4:40am
Welcome to issue 300 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers from July 13 to 26, 2014 Looks like we are chuck-full of goodies this time around! Enjoy! Quotes of the Week * Cale: Functions aren't monads, the type constructor (->) e is a monad * glguy: There's no achievement for using all the operators * benmachine: adoption by lots of people may stunt progress of haskell, but it will probably help the progress of people Top Reddit Stories * Somehow, this happened. Haskell Ryan Gosling. Domain: haskellryangosling.tumblr.com, Score: 144, Comments: 31 Original: [1] http://goo.gl/IQ2f3s On Reddit: [2] http://goo.gl/H24aRa * Papers every haskeller should read Domain: self.haskell, Score: 104, Comments: 35 Original: [3] http://goo.gl/R7uGSB On Reddit: [4] http://goo.gl/R7uGSB * Strict Language Pragma Proposal Domain: ghc.haskell.org, Score: 86, Comments: 95 Origin
Categories: Offsite Discussion