- Haskell-Cafe - Haskell.org

Functional programming and William Lawvere's notion of "variable sets"(vs topos of "static sets") in a Topos ...
by Vasili I. Galchin 04 Aug '14

04 Aug '14

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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Re: [Haskell-cafe] Fwd: Default stdout buffering of child process of createProcess
by Doug McIlroy 04 Aug '14

04 Aug '14

>> I still think haskell is using screwy defaults for stdout buffering. > Line buffered would be an inefficient default. Stdout is fully buffered in > c99 if it can be determined that it is not attached to a terminal. Putting efficiency before efficacy is un-Haskellian. How can the required determination be implemented? Stdout may be attached to a terminal indirectly through a pipeline. It may be "attached" through a file that another process is watching. It may be attached to some other real-time device or system. Buffering can cause unbounded delays in systems with sporadic input. And it can cause deadlock in systems that employ feedback, as most systems do. Terminals, for example, are unbuffered not merely because users are impatient, but more critically because users are feedback agents. Because the effects of buffering are not transparent, it would be wise to make it an optional optimization, not a default.

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"Standardising" Haskell AST for tooling
by Alan & Kim Zimmerman 03 Aug '14

03 Aug '14

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 doing? Is it being done already, or planned? Regards Alan

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Bad interaction of inlinePerformIO and mutable vectors
by Michael Snoyman 03 Aug '14

03 Aug '14

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, the reference is updated. I'm testing on GHC 7.8.3, Ubuntu 64-bit, and compiling with -O2. I'm curious if anyone has an idea as to why there is this difference in behavior. Michael [1] http://lpaste.net/108483

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http://www.downforeveryoneorjustme.com/haskell.org
by Tim C. Schroeder 03 Aug '14

03 Aug '14

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

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Haskell Platform 2014.2.0.0 Release Candidate 4 (Windows only)
by Mark Lentczner 03 Aug '14

03 Aug '14

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…> - HaskellPlatform-2014.2.0.0-x86_64-RC4-setup.exe <http://www.ozonehouse.com/mark/platform/HaskellPlatform-2014.2.0.0-x86_64-R…> - 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 reasonably wary: shasum -a 256: 975e014d53cfdb84036889923d6e9598e4623baa9c69d53dc4d9372fe100cf95 HaskellPlatform-2014.2.0.0-i386-RC4-setup.exe 05b39901cdc43de335583c461bcd77c0d8dd5765ab195ad387a0dc774a43bee2 HaskellPlatform-2014.2.0.0-x86_64-RC4-setup.exe

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unfoldr with a little extra
by David Feuer 03 Aug '14

03 Aug '14

Edward Kmett's NonEmpty module has a version of unfoldr (there just called unfoldr) for non-empty lists that seems also to be useful when applied to regular lists: unfoldr1::(b -> (a, Maybe b)) -> b -> [a] unfoldr1 f b= go b where go q = case f q of (a,may_b) -> a : maybe [] go may_b My question is whether it is possible to write this function using the usual unfoldr. I have the feeling there might be some way, but I just can't see it. David

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typed tagless-final interpretation examples broken with recent ghc
by Mathijs Kwik 02 Aug '14

02 Aug '14

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

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re-reading a Samson Abramsky paper ..
by Vasili I. Galchin 02 Aug '14

02 Aug '14

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" ...

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Re: [Haskell-cafe] Tor project
by Adam Wick 02 Aug '14

02 Aug '14

Hi - Yes, we (Galois) are. The end goal is to have a Tor implementation running on a HaLVM. Right now the project is internal, but the plan is to push a basic relay node implementation out to our GitHub site sometime in the next few weeks. As for TLS, it is possible that timing attacks based on a functional language implementation could be more likely than those for a traditional C implementation. On the other hand, functional language implementations protect you from a wide variety of attacks that occur in C implementations. I don’t believe the balance has been studied, but it’d be interesting. I do know the OCaml/Mirage folks have been having good luck with their TLS implementation. I believe they’ve at least started doing some red team analysis of it, as well, with good results. See their various blog posts, starting with http://openmirage.org/blog/introducing-ocaml-tls. I’m not sure if Vincent’s library has been subject to similar evaluation, and I know the partial library in our Tor implementation has not been. - Adam Quoth: > I’ll make a question out of it: > > Is anyone working on a Haskell project compatible with Tor? Library, Server, Browser, etc. > Is anyone interested in such a project? > Would the Haskell Runtime and TLS modules have any time dependent behavior that would make encryption harder/easier to break than C implementations? Basically, is the TLS attach surface smaller or larger than openssl and is there any data to support claims of such?

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EsseOS: Haskell-based tailored services for the cloud
by Vo Minh Thu 01 Aug '14

01 Aug '14

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

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ICFP 2014 Final Call for Participation
by David Van Horn 01 Aug '14

01 Aug '14

[ 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 * Local arrangements (including travel and accommodation): http://icfpconference.org/icfp2014/local.html * Registration is available via: https://regmaster4.com/2014conf/ICFP14/register.php Early registration is due 3 August, 2014. * Programming contest, 25-28 July, 2014: http://icfpcontest.org/ * Follow @icfp_conference on twitter for the latest news: http://twitter.com/#!/icfp_conference Keynote speakers: * Kathleen Fisher (Tufts University): Using Formal Methods to Enable More Secure Vehicles: DARPA's HACMS Program * Robert Bruce Findler (Northwestern University): Behavioral Software Contracts * Stephanie Weirich (University of Pennsylvania): Depending on Types There are several events affiliated with ICFP: Sunday, August 31 ACM SIGPLAN Workshop on Generic Programming ACM SIGPLAN Workshop on Higher-order Programming with Effects Monday, September 1 – Wednesday, September 3 ICFP Thursday, September 4 ACM SIGPLAN Commercial Users of Functional Programming: Day 1, Tutorials ACM SIGPLAN Haskell Symposium: Day 1 ACM SIGPLAN Workshop on Functional High-Performance Computing ACM SIGPLAN ML Family Workshop Friday, September 5 ACM SIGPLAN Commercial Users of Functional Programming: Day 2, Tutorials ACM SIGPLAN Haskell Symposium: Day 2 ACM SIGPLAN OCaml Workshop ACM SIGPLAN Erlang Workshop Saturday, September 6 ACM SIGPLAN Commercial Users of Functional Programming: Day 3, Talks ACM SIGPLAN Haskell Implementors Workshop ACM SIGPLAN Workshop on Functional Art, Music, Modeling and Design Conference Organizers General Chair: Johan Jeuring, Utrecht University Program Chair: Manuel Chakravarty, University of New South Wales Local Arrangements Chair: Björn von Sydow, Chalmers University Industrial Relations Chair: Anil Madhavapeddy, University of Cambridge Workshop Co-Chairs: Tom Schrijvers, Ghent University Sam Tobin-Hochstadt, Indiana University Programming Contest Co-Chairs: Duncan Coutts, Well Typed LLP Nicolas Wu, University of Oxford Student Research Competition Chair: Meng Wang, Chalmers University Publicity Chair: David Van Horn, University of Maryland Video Chair: Iavor Diatchki, Galois Malcolm Wallace, Standard Chartered Bank Industrial partners: Platinum partners Jane Street Capital Gold partners Google Microsoft Research Mozilla Oracle Labs Standard Chartered Bank Silver partners Bloomberg Credit Suisse CyberPoint Erlang Solutions Facebook Galois Klarna Lexifi Twitter Bronze partners Alephcloud IntelliFactory Opera Software QuviQ Systeor Vest AS =====================================================================

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haskell on Debian
by Kees Bleijenberg 01 Aug '14

01 Aug '14

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?

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Tor project and Haskell (FPL) ,..
by Vasili I. Galchin 01 Aug '14

01 Aug '14

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

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Re: [Haskell-cafe] Tor project
by Tobias Dammers 01 Aug '14

01 Aug '14

On Fri, Aug 01, 2014 at 12:03:34PM +0200, Wojciech Narczyński wrote: > > W dniu 2014-08-01 11:56, Tobias Dammers pisze: > >On Fri, Aug 01, 2014 at 09:35:37AM +0200, Wojtek Narczyński wrote: > >>Why the gimmick, for each and every piece of crypto code? Why not just use > >>the clock for timing? The crypto lib would probably have to tune itself on > >>startup. > >Sorry, I didn't mean use the crypto function to cause the delay; I meant > >using a cryptographic hash to determine how long the delay should be. > >Once we have a number, the system clock should of course be used to > >actually delay things. > > > > > This is poinlessly complicated. > > Just measure how much each execution takes, remove outliers, take the upper > bound, wait appropriate amount of time on each call so that the attacker > sees constant time for each call. > I think you are underestimating the statistical aspect to this. In order to do this in a useful way, you'd have to sample your own code on a regular basis, for a large number of inputs, and you better get the padding exactly right, because if it's off by a tiny amount, that tiny amount will remain after averaging. It will basically boil down to a sampling war between you and the attacker - if your sampling is really good, your error may be really small, but the attacker can counter this by sampling more. To make matters worse, you are playing this game blindly: you don't know how much sampling is enough, or how much the attacker can afford to sample. I also think you are over-estimating the complexity of the crypto-hash solution: suitable hashing functions are there for the taking (it doesn't even have to be a time-hard function like bcrypt/scrypt/... AFAIK, just one that's cryptographically sound), converting a hash into a delay value is trivial, and you need to implement a delay mechanism anyhow. The most "challenging" part, I think, is managing a secret to seed the hash function.

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Re: [Haskell-cafe] www.galois.com vs Google??
by Vasili I. Galchin 01 Aug '14

01 Aug '14

Tobias, I pretty agree with your response. I was trying to challenge the entire audience to think about the issue about software correctness(e.g. strong typefullness (and static type checking) like Haskell, et. al. vs no type-checking/ dynamic type checking). My point is how can we as a community respond to Google's challenge?? In my humble opinion (IMHO) I think Google has missed the point regarding contemporary software correctness problems .. (and also the Tor project . given the languages of implementation) .. Here is a very simple and cheesy example .. I worked at HP on a contract .. . a predecessor of mine used with typefullnes of C++ (I thinking using type casting ) and did a buffer overrun of "heap" allocated that corrupted "the heap allocator metadata" (malloc) .... of course I used to "gdb" to do a "postmordum after the patient died" ... IHMO I would been more happier if this "overrun" had been detected at compile-tyime .. due to static strong type checking ... :-) Alll grammer errors are due to my cat Buddy ... Vasya On Thu, Jul 31, 2014 at 5:24 AM, Tobias Dammers <tdammers(a)gmail.com> wrote: > The way I read that article, those are two very different goals and > approaches. > > The "Project Zero" thing seems to be about subjecting "everything" to > thorough security checking by the best experts Google can buy, in order > to fix as many security problems on the internet as they possibly can. > > The software correctness problem is somewhat related, but not entirely - > not all security problems are software bugs, and not all software bugs > are security problems. > > On a side note, I think both problems are inherently unsolvable - we can > go a long way cleaning up the solvable problems, and building an > infrastructure that avoids them by design, but some potential for bugs > and flaws will always remain, at least as long as we're using reasonable > definitions of "programming" and "software". > > On Wed, Jul 30, 2014 at 10:08:06PM -0500, Vasili I. Galchin wrote: >> Hello Haskellers(and all FPL people), >> >> I just ran across the following effort by Google: >> http://blogs.techworld.com/war-on-error/2014/07/googles-project-zero-flaw-p… >> >> It seems to me that www.galois.com(www.janestreetcapital.com) >> realizes that the solution to software correctness problems doesn't >> lie with uncontrolled "mutability" ... >> >> Question: does Google concur with www.galois.com or google's >> effort just "more of the same"?? >> >> Vasili >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe

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Haskell Platform 2014.2.0.0 Release Candidate 3
by Mark Lentczner 31 Jul '14

31 Jul '14

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…> - 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…> *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 - small fixes to allow bootstrapping the platform with GHC 7.4 - README and LICENSE updated *Source Tarball* - all missing pieces now present - build platfrom from source tarball verified *Generic Linux Binary Dist* - Built from the GHC's generic Linux bindist for Deb 7 style systems - Complete tarball: this is all you need to install Haskell on a compatible system - Built on Ubuntu 12.04LTS - Tested on Ubuntu 14 - my system needed a symlink from libgmp.so to libgmp.so.10 - this seems to be an issue with the GHC bindist built components To install this: cd / sudo tar xvf ~/haskell-platform-2014.2.0.0-unknown-linux-x86_64-RC3.tar.gz sudo /usr/local/haskell/ghc-7.8.3-x8_64/bin/activate-hs This will finish the package registration, and install symlinks from /usr/local/bin for all the standard haskell command line tools. — Mark *shasum -a 256:* ab759ec50618f2604163eca7ad07e50c8292398a2d043fdc1012df161b2eb89a haskell-platform-2014.2.0.0-srcdist-RC3.tar.gz 0da6879ae657481849e7ec4e5d3c4c035e090824167f97434b48af297ec17cf9 haskell-platform-2014.2.0.0-unknown-linux-x86_64-RC3.tar.gz

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[ANN] hsimport 0.5: configurable pretty printing and placing of imports
by Daniel Trstenjak 31 Jul '14

31 Jul '14

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

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Tor project
by Vasili I. Galchin 31 Jul '14

31 Jul '14

Haskell contributions to http://www.torproject.org .. .any thoughts ??

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Intuition to understand poor man's concurrency
by martin 31 Jul '14

31 Jul '14

Hello all, I am trying to understand the ideas of Koen Klaessen, published in Functional Pearls: "A poor man's concurrency" (1993). The code in the paper doesn't compile. E.g. uses "lambda dot" instead of "labmda arrow", i.e. the way the labmda calculus guys write things. Was that ever legal haskell or is this the result of some lhs2lex pretty printer? Anyways, I believe I was able to convert that into modern haskell syntax - at least it compiles. But I have trouble to understand the Monad instance presented there. Could anyobody walk me through the bind function? But even more important: how do you guys develop an intuition about what the bind operator does in a specific monad. I saw a Google tech talk where Douglas Crockford explains mondads in terms of Objects in javascript (https://www.youtube.com/watch?v=b0EF0VTs9Dc) which was certainly enlightening, but I couldn't apply it to this particular modad. I also tried using something like Data Flow Diagrams. This kinda works for simple Mondads such as the state mondad, but I couldn't apply it to the concurrency mondad. In general DFDs are not very good when it comes to higher order functions. In any case here is the code. I made it more verbose than necessary in order to understand it (bind was originally just one line), but to no avail. newtype C m a = C ((a -> Action m) -> Action m) instance Monad m => Monad (C m) where (C m) >>= k = C cont where cont c = m (\a -> let C h = k a in h c) return x = C $ \c -> c x data Action m = Atom (m (Action m)) | Fork (Action m) (Action m) | Stop

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Newtype derivation understanding problem
by Konstantine Rybnikov 31 Jul '14

31 Jul '14

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/Intern… [1]: https://github.com/snapframework/snap/blob/0.13.2.8/src/Snap/Snaplet/Intern…

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Haskell Weekly News: Issue 300
by Daniel Santa Cruz 31 Jul '14

31 Jul '14

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 Original: [5] http://goo.gl/Yq28yt On Reddit: [6] http://goo.gl/BlmXpA * Announcing engine-io and socket-io for Haskell Domain: ocharles.org.uk, Score: 81, Comments: 7 Original: [7] http://goo.gl/PGW8Y8 On Reddit: [8] http://goo.gl/IsGRGi * The Haskell Cast #8 - Ollie Charles on 24 Days of Hackage and Nix Domain: haskellcast.com, Score: 70, Comments: 12 Original: [9] http://goo.gl/jBc9bk On Reddit: [10] http://goo.gl/syhwPd * Blazing Fast HTML - Virtual DOM in Elm Domain: elm-lang.org, Score: 60, Comments: 28 Original: [11] http://goo.gl/3luwtw On Reddit: [12] http://goo.gl/88zNkZ * Idris 0.9.14 released, with updated JavaScript backend, quasiquotes, and lots of internal cleanups and improvements Domain: idris-lang.org, Score: 55, Comments: 11 Original: [13] http://goo.gl/wmW3RM On Reddit: [14] http://goo.gl/fN28z6 * hoodle 0.3 released - free pen note taking program Domain: ianwookim.org, Score: 53, Comments: 15 Original: [15] http://goo.gl/jauFC On Reddit: [16] http://goo.gl/upMnf6 * This just in, from my local GHC/Cabal checkout... (re: Cabal Hell) Domain: self.haskell, Score: 52, Comments: 13 Original: [17] http://goo.gl/tD2yOg On Reddit: [18] http://goo.gl/tD2yOg * Haskell for all: Equational reasoning at scale Domain: haskellforall.com, Score: 52, Comments: 29 Original: [19] http://goo.gl/BZtZ4R On Reddit: [20] http://goo.gl/xKxCM3 * Complete roadmap from total novice to Haskell mastery? Domain: self.haskell, Score: 50, Comments: 74 Original: [21] http://goo.gl/5y1lXA On Reddit: [22] http://goo.gl/5y1lXA * Write webservices around databases with 0 boilerplate: announcing servant 0.1 Domain: alpmestan.com, Score: 50, Comments: 16 Original: [23] http://goo.gl/vzz8aT On Reddit: [24] http://goo.gl/qTty6u * Mutable Algorithms in Immutable Languages, Part 3 Domain: tel.github.io, Score: 49, Comments: 2 Original: [25] http://goo.gl/uG5Bds On Reddit: [26] http://goo.gl/qrdk6Y * Best Practices for Avoiding Cabal Hell Domain: softwaresimply.blogspot.com, Score: 47, Comments: 13 Original: [27] http://goo.gl/OqG241 On Reddit: [28] http://goo.gl/fapyz2 * Applicative (Make) vs Monadic (Shake) build systems Domain: neilmitchell.blogspot.co.uk, Score: 47, Comments: 7 Original: [29] http://goo.gl/CPyzpd On Reddit: [30] http://goo.gl/2eW8Ed * Nemnem - Haskell source hyperlinker Domain: robinp.github.io, Score: 41, Comments: 33 Original: [31] http://goo.gl/2msbLR On Reddit: [32] http://goo.gl/R6hBOl * Let me tell you about the types of data Domain: tel.github.io, Score: 41, Comments: 51 Original: [33] http://goo.gl/ZjJelo On Reddit: [34] http://goo.gl/bbmXSW * Lens Tutorial - Introduction (part 1) Domain: blog.jakubarnold.cz, Score: 39, Comments: 11 Original: [35] http://goo.gl/yQRoPY On Reddit: [36] http://goo.gl/fnbZ0F * Help - I wrote some Haskell code, it works, but it's slower than Python. What did I do wrong? Domain: self.haskell, Score: 39, Comments: 43 Original: [37] http://goo.gl/CG13CR On Reddit: [38] http://goo.gl/CG13CR * IntrinsicSuperclasses for Haskell (new proposal for default superclass instances by Conor McBride) Domain: ghc.haskell.org, Score: 37, Comments: 10 Original: [39] http://goo.gl/vDYUQh On Reddit: [40] http://goo.gl/vZjHXS * hackage-diff: Compare the public API of different versions of a Hackage library Domain: self.haskell, Score: 37, Comments: 32 Original: [41] http://goo.gl/y682CB On Reddit: [42] http://goo.gl/y682CB * How do you avoid the Cabal Hell™? Domain: self.haskell, Score: 36, Comments: 30 Original: [43] http://goo.gl/9uS54H On Reddit: [44] http://goo.gl/9uS54H * Edward Kmett on Hask Domain: youtu.be, Score: 35, Comments: 34 Original: [45] http://goo.gl/1lfywk On Reddit: [46] http://goo.gl/D0AuFQ * Mutable Algorithms in Immutable Languages, Part 2 Domain: tel.github.io, Score: 33, Comments: 1 Original: [47] http://goo.gl/g0ylvT On Reddit: [48] http://goo.gl/jwwr87 * Multi-instance packages status report Domain: permalink.gmane.org, Score: 32, Comments: 7 Original: [49] http://goo.gl/JSPx39 On Reddit: [50] http://goo.gl/2rzPJL * Slides from Conan Elliott's workshop on Denotational Design: from meanings to programs Domain: conal.net, Score: 32, Comments: 6 Original: [51] http://goo.gl/GwO4Fv On Reddit: [52] http://goo.gl/0u9KVl * Reactive-banana anti-tutorial Domain: gelisam.blogspot.ca, Score: 31, Comments: 23 Original: [53] http://goo.gl/D7mv4X On Reddit: [54] http://goo.gl/shMY0N * Intro to Machines & Arrows Part 2: 'Auto' as Category, Applicative & Arrow, ft. locally stateful compositions; Further down the road to an Arrowized FRP implementation. Domain: blog.jle.im, Score: 28, Comments: 9 Original: [55] http://goo.gl/xkwocR On Reddit: [56] http://goo.gl/phqXn8 Top StackOverflow Questions * Examples of histomorphisms in Haskell votes: 16, answers: 2 Read on SO: [57] http://goo.gl/ZmGzI6 * Plan B, or what's the opposite of Maybe's >>=? votes: 15, answers: 2 Read on SO: [58] http://goo.gl/rYWlzQ * Let-renaming function breaks code votes: 14, answers: 2 Read on SO: [59] http://goo.gl/R9CGyL * Pattern matching on rank-2 type votes: 14, answers: 3 Read on SO: [60] http://goo.gl/s0IszK * Haskell algorithm advice and suggestions for alternate solutions votes: 14, answers: 1 Read on SO: [61] http://goo.gl/2l23N8 * Why can't Haskell be tricked into performing IO operations by using strict evaluation? votes: 14, answers: 2 Read on SO: [62] http://goo.gl/Ey9795 * How does lifting (in a functional programming context) relate to category theory? votes: 14, answers: 1 Read on SO: [63] http://goo.gl/esTTbO Until next time, [64]+Daniel Santa Cruz References 1. http://haskellryangosling.tumblr.com/ 2. http://www.reddit.com/r/haskell/comments/2avnc0/somehow_this_happened_haske… 3. http://www.reddit.com/r/haskell/comments/2blsqa/papers_every_haskeller_shou… 4. http://www.reddit.com/r/haskell/comments/2blsqa/papers_every_haskeller_shou… 5. https://ghc.haskell.org/trac/ghc/wiki/StrictPragma 6. http://www.reddit.com/r/haskell/comments/2bi69g/strict_language_pragma_prop… 7. https://ocharles.org.uk/blog/posts/2014-07-13-announcing-socket-io-for-hask… 8. http://www.reddit.com/r/haskell/comments/2aks91/announcing_engineio_and_soc… 9. http://www.haskellcast.com/episode/008-ollie-charles-on-24-days-of-hackage-… 10. http://www.reddit.com/r/haskell/comments/2bbc82/the_haskell_cast_8_ollie_ch… 11. http://elm-lang.org/blog/Blazing-Fast-Html.elm 12. http://www.reddit.com/r/haskell/comments/2bam6p/blazing_fast_html_virtual_d… 13. http://www.idris-lang.org/idris-0-9-14-released/ 14. http://www.reddit.com/r/haskell/comments/2aw6vl/idris_0914_released_with_up… 15. http://ianwookim.org/hoodle/ 16. http://www.reddit.com/r/haskell/comments/2aotln/hoodle_03_released_free_pen… 17. http://www.reddit.com/r/haskell/comments/2b7odl/this_just_in_from_my_local_… 18. http://www.reddit.com/r/haskell/comments/2b7odl/this_just_in_from_my_local_… 19. http://www.haskellforall.com/2014/07/equational-reasoning-at-scale.html 20. http://www.reddit.com/r/haskell/comments/2b7xwx/haskell_for_all_equational_… 21. http://www.reddit.com/r/haskell/comments/2ali12/complete_roadmap_from_total… 22. http://www.reddit.com/r/haskell/comments/2ali12/complete_roadmap_from_total… 23. http://alpmestan.com/posts/2014-07-26-announcing-servant.html 24. http://www.reddit.com/r/haskell/comments/2bs536/write_webservices_around_da… 25. http://tel.github.io/2014/07/15/mutable_algorithms_in_immutable_languages_p… 26. http://www.reddit.com/r/haskell/comments/2ase1q/mutable_algorithms_in_immut… 27. http://softwaresimply.blogspot.com/2014/07/haskell-best-practices-for-avoid… 28. http://www.reddit.com/r/haskell/comments/2ameew/best_practices_for_avoiding… 29. http://neilmitchell.blogspot.co.uk/2014/07/applicative-vs-monadic-build-sys… 30. http://www.reddit.com/r/haskell/comments/2blex3/applicative_make_vs_monadic… 31. http://robinp.github.io/nemnem/ 32. http://www.reddit.com/r/haskell/comments/2ata3n/nemnem_haskell_source_hyper… 33. http://tel.github.io/2014/07/23/types_of_data/ 34. http://www.reddit.com/r/haskell/comments/2bj7it/let_me_tell_you_about_the_t… 35. http://blog.jakubarnold.cz/2014/07/14/lens-tutorial-introduction-part-1.html 36. http://www.reddit.com/r/haskell/comments/2ap02f/lens_tutorial_introduction_… 37. http://www.reddit.com/r/haskell/comments/2brxwp/help_i_wrote_some_haskell_c… 38. http://www.reddit.com/r/haskell/comments/2brxwp/help_i_wrote_some_haskell_c… 39. https://ghc.haskell.org/trac/ghc/wiki/IntrinsicSuperclasses 40. http://www.reddit.com/r/haskell/comments/2avs16/intrinsicsuperclasses_for_h… 41. http://www.reddit.com/r/haskell/comments/2b5jfd/hackagediff_compare_the_pub… 42. http://www.reddit.com/r/haskell/comments/2b5jfd/hackagediff_compare_the_pub… 43. http://www.reddit.com/r/haskell/comments/2al3vx/how_do_you_avoid_the_cabal_… 44. http://www.reddit.com/r/haskell/comments/2al3vx/how_do_you_avoid_the_cabal_… 45. http://youtu.be/Klwkt9oJwg0 46. http://www.reddit.com/r/haskell/comments/2b3rk5/edward_kmett_on_hask/ 47. http://tel.github.io/2014/07/13/mutable_algorithms_in_immutable_languages_p… 48. http://www.reddit.com/r/haskell/comments/2al4cw/mutable_algorithms_in_immut… 49. http://permalink.gmane.org/gmane.comp.lang.haskell.ghc.devel/5413 50. http://www.reddit.com/r/haskell/comments/2bbys6/multiinstance_packages_stat… 51. http://conal.net/talks/lambdajam-2014.pdf 52. http://www.reddit.com/r/haskell/comments/2brioe/slides_from_conan_elliotts_… 53. http://gelisam.blogspot.ca/2014/07/reactive-banana-anti-tutorial.html 54. http://www.reddit.com/r/haskell/comments/2auswf/reactivebanana_antitutorial/ 55. http://blog.jle.im/entry/auto-as-category-applicative-arrow-intro-to-machin… 56. http://www.reddit.com/r/haskell/comments/2aot3i/intro_to_machines_arrows_pa… 57. http://stackoverflow.com/questions/24884475/examples-of-histomorphisms-in-h… 58. http://stackoverflow.com/questions/24902463/plan-b-or-whats-the-opposite-of… 59. http://stackoverflow.com/questions/24724738/let-renaming-function-breaks-co… 60. http://stackoverflow.com/questions/24744294/pattern-matching-on-rank-2-type 61. http://stackoverflow.com/questions/24748750/haskell-algorithm-advice-and-su… 62. http://stackoverflow.com/questions/24775528/why-cant-haskell-be-tricked-int… 63. http://stackoverflow.com/questions/24856963/how-does-lifting-in-a-functiona… 64. https://plus.google.com/105107667630152149014/about

1 0

www.galois.com vs Google??
by Vasili I. Galchin 31 Jul '14

31 Jul '14

Hello Haskellers(and all FPL people), I just ran across the following effort by Google: http://blogs.techworld.com/war-on-error/2014/07/googles-project-zero-flaw-p… It seems to me that www.galois.com(www.janestreetcapital.com) realizes that the solution to software correctness problems doesn't lie with uncontrolled "mutability" ... Question: does Google concur with www.galois.com or google's effort just "more of the same"?? Vasili

1 0

The ML Family workshop: program and the 2nd call for participation
by oleg＠okmij.org 31 Jul '14

31 Jul '14

Higher-order, Typed, Inferred, Strict: ACM SIGPLAN ML Family Workshop Thursday September 4, 2014, Gothenburg, Sweden Call For Participation and Program http://okmij.org/ftp/ML/ML14.html Early registration deadline is August 3. Please register at https://regmaster4.com/2014conf/ICFP14/register.php The workshop is conducted in close cooperation with the OCaml Users and Developers Workshop http://ocaml.org/meetings/ocaml/2014/ taking place on September 5. *** Program with short summaries *** (The online version links to the full 2-page abstracts) * Welcome 09:00 * Session 1: Module Systems 09:10 - 10:00 1ML -- core and modules as one (Or: F-ing first-class modules) Andreas Rossberg We propose a redesign of ML in which modules are first-class values. Functions, functors, and even type constructors are one and the same construct. Likewise, no distinction is made between structures, records, or tuples, including tuples over types. Yet, 1ML does not depend on dependent types, and its type structure is expressible in terms of plain System F-omega, in a minor variation of our F-ing modules approach. Moreover, it supports (incomplete) Hindley/Milner-style type inference. Both is enabled by a simple universe distinction into small and large types. Type-level module aliases: independent and equal Jacques Garrigue; Leo White We promote the use of type-level module aliases, a trivial extension of the ML module system, which helps avoiding code dependencies, and provides an alternative to strengthening for type equalities. * Session 2: Beyond Hindley-Milner 10:30 - 11:20 The Rust Language and Type System (Demo) Felix Klock; Nicholas Matsakis Rust is a new programming language for developing reliable and efficient systems. It is designed to support concurrency and parallelism in building applications and libraries that take full advantage of modern hardware. Rust's static type system is safe and expressive and provides strong guarantees about isolation, concurrency, and memory safety. Rust also offers a clear performance model, making it easier to predict and reason about program efficiency. One important way it accomplishes this is by allowing fine-grained control over memory representations, with direct support for stack allocation and contiguous record storage. The language balances such controls with the absolute requirement for safety: Rust's type system and runtime guarantee the absence of data races, buffer overflows, stack overflows, and accesses to uninitialized or deallocated memory. In this demonstration, we will briefly review the language features that Rust leverages to accomplish the above goals, focusing in particular on Rust's advanced type system, and then show a collection of concrete examples of program subroutines that are efficient, easy for programmers to reason about, and maintain the above safety property. Doing web-based data analytics with F# (Informed Position) Tomas Petricek; Don Syme With type providers that integrate external data directly into the static type system, F# has become a fantastic language for doing data analysis. Rather than looking at F# features in isolation, this paper takes a holistic view and presents the F# approach through a case study of a simple web-based data analytics platform. * Session 3: Verification 11:40 - 12:30 Well-typed generic smart-fuzzing for APIs (Experience report) Thomas Braibant; Jonathan Protzenko; Gabriel Scherer In spite of recent advances in program certification, testing remains a widely-used component of the software development cycle. Various flavors of testing exist: popular ones include unit testing, which consists in manually crafting test cases for specific parts of the code base, as well as quickcheck-style testing, where instances of a type are automatically generated to serve as test inputs. These classical methods of testing can be thought of as internal testing: the test routines access the internal representation of the data structures to be checked. We propose a new method of external testing where the library only deals with a module interface. The data structures are exported as abstract types; the testing framework behaves like regular client code and combines functions exported by the module to build new elements of the various abstract types. Any counter-examples are then presented to the user. Furthermore, we demonstrate that this methodology applies to the smart-fuzzing of security APIs. Improving the CakeML Verified ML Compiler Ramana Kumar; Magnus O. Myreen; Michael Norrish; Scott Owens The CakeML project comprises a mechanised semantics for a subset of Standard ML and a formally verified compiler. We will discuss our plans for improving and applying CakeML in four directions: optimisations, new primitives, a library, and verified applications. * Session 4: Implicits 14:00 - 14:50 Implicits in Practice (Demo) Nada Amin; Tiark Rompf Popularized by Scala, implicits are a versatile language feature that are receiving attention from the wider PL community. This demo will present common use cases and programming patterns with implicits in Scala. Modular implicits Leo White; Frédéric Bour We propose a system for ad-hoc polymorphism in OCaml based on using modules as type-directed implicit parameters. * Session 5: To the bare metal 15:10 - 16:00 Metaprogramming with ML modules in the MirageOS (Experience report) Anil Madhavapeddy; Thomas Gazagnaire; David Scott; Richard Mortier In this talk, we will go through how MirageOS lets the programmer build modular operating system components using a combination of functors and metaprogramming to ensure portability across both Unix and Xen, while preserving a usable developer workflow. Compiling SML# with LLVM: a Challenge of Implementing ML on a Common Compiler Infrastructure Katsuhiro Ueno; Atsushi Ohori We report on an LLVM backend of SML#. This development provides detailed accounts of implementing functional language functionalities in a common compiler infrastructure developed mainly for imperative languages. We also describe techniques to compile SML#'s elaborated features including separate compilation with polymorphism, and SML#'s unboxed data representation. * Session 6: No longer foreign 16:30 - 18:00 A Simple and Practical Linear Algebra Library Interface with Static Size Checking (Experience report) Akinori Abe; Eijiro Sumii While advanced type systems--specifically, dependent types on natural numbers--can statically ensure consistency among the sizes of collections such as lists and arrays, such type systems generally require non-trivial changes to existing languages and application programs, or tricky type-level programming. We have developed a linear algebra library interface that guarantees consistency (with respect to dimensions) of matrix (and vector) operations by using generative phantom types as fresh identifiers for statically checking the equality of sizes (i.e., dimensions). This interface has three attractive features in particular. (i) It can be implemented only using fairly standard ML types and its module system. Indeed, we implemented the interface in OCaml (without significant extensions like GADTs) as a wrapper for an existing library. (ii) For most high-level operations on matrices (e.g., addition and multiplication), the consistency of sizes is verified statically. (Certain low-level operations, like accesses to elements by indices, need dynamic checks.) (iii) Application programs in a traditional linear algebra library can be easily migrated to our interface. Most of the required changes can be made mechanically. To evaluate the usability of our interface, we ported to it a practical machine learning library (OCaml-GPR) from an existing linear algebra library (Lacaml), thereby ensuring the consistency of sizes. SML3d: 3D Graphics for Standard ML (Demo) John Reppy The SML3d system is a collection of libraries designed to support real-time 3D graphics programming in Standard ML (SML). This paper gives an overview of the system and briefly highlights some of the more interesting aspects of its design and implementation. * Poster presentation, at the joint poster session with the OCaml workshop Nullable Type Inference Michel Mauny; Benoit Vaugon We present a type system for nullable types in an ML-like programming language. We start with a simple system, presented as an algorithm, whose interest is to introduce the formalism that we use. We then extend it as system using subtyping constraints, that accepts more programs. We state the usual properties for both systems. This is work in progress. Program Committee Kenichi Asai Ochanomizu University, Japan Matthew Fluet Rochester Institute of Technology, USA Jacques Garrigue Nagoya University, Japan Dave Herman Mozilla, USA Stefan Holdermans Vector Fabrics, Netherlands Oleg Kiselyov (Chair) University of Tsukuba, Japan Keiko Nakata Tallinn University of Technology, Estonia Didier Remy INRIA Paris-Rocquencourt, France Zhong Shao Yale University, USA Hongwei Xi Boston University, USA

1 0

Deduce issue.
by Magicloud Magiclouds 30 Jul '14

30 Jul '14

Hi, I have code like follow. And compiling gave me error as the last part. What should I do? ``` class WidgetClass w data Widget = forall a. WidgetClass a => Widget a instance WidgetClass Widget lookupWin :: (WidgetClass w) => WINDOW -> w -> Maybe w lookupWin xwin widget = if widgetWindowId widget == xwin then Just widget else foldl (\a (Widget b) -> maybe (lookupWin xwin b) Just a ) Nothing $ widgetChildren widget ``` --- ``` Graphics/HUI/Widget.hs:15:23: Could not deduce (w ~ a) from the context (WidgetClass w) bound by the type signature for lookupWin :: WidgetClass w => WINDOW -> w -> Maybe w at Graphics/HUI/Widget.hs:10:14-54 or from (WidgetClass a) bound by a pattern with constructor Widget :: forall a. WidgetClass a => a -> Widget, in a lambda abstraction at Graphics/HUI/Widget.hs:14:19-26 ‘w’ is a rigid type variable bound by the type signature for lookupWin :: WidgetClass w => WINDOW -> w -> Maybe w at Graphics/HUI/Widget.hs:10:14 ‘a’ is a rigid type variable bound by a pattern with constructor Widget :: forall a. WidgetClass a => a -> Widget, in a lambda abstraction at Graphics/HUI/Widget.hs:14:19 Expected type: Maybe w Actual type: Maybe a Relevant bindings include b :: a (bound at Graphics/HUI/Widget.hs:14:26) a :: Maybe w (bound at Graphics/HUI/Widget.hs:14:16) widget :: w (bound at Graphics/HUI/Widget.hs:11:16) lookupWin :: WINDOW -> w -> Maybe w (bound at Graphics/HUI/Widget.hs:11:1) In the first argument of ‘maybe’, namely ‘(lookupWin xwin b)’ In the expression: maybe (lookupWin xwin b) Just a ``` -- 竹密岂妨流水过山高哪阻野云飞 And for G+, please use magiclouds#gmail.com.

2 4

redundant loads and saves in code generated for recursive functions?
by Jyotirmoy Bhattacharya 30 Jul '14

30 Jul '14

Dear All, I am new to Haskell so please forgive me if I am asking about something already well-understood. I was trying to understand the performance of my Haskell program compiled with the LLVM backend. I used -ddump-llvm to dump the LLVM assembly and then ran llc -O3 on the resulting file to look at the native assembly. One of the generated function starts off with s5BH_info: # @s5BH_info # BB#0: subq $208, %rsp movq %r13, 200(%rsp) movq %rbp, 192(%rsp) movq %r12, 184(%rsp) movq %rbx, 176(%rsp) movq %r14, 168(%rsp) movq %rsi, 160(%rsp) movq %rdi, 152(%rsp) movq %r8, 144(%rsp) movq %r9, 136(%rsp) movq %r15, 128(%rsp) movss %xmm1, 124(%rsp) movss %xmm2, 120(%rsp) movss %xmm3, 116(%rsp) movss %xmm4, 112(%rsp) movsd %xmm5, 104(%rsp) movsd %xmm6, 96(%rsp) At some point down the line the function makes a tail call to itself and this is the code generated movq %r14, 168(%rsp) movq 200(%rsp), %r13 movq 192(%rsp), %rbp movq 184(%rsp), %r12 movq 176(%rsp), %rbx movq 128(%rsp), %r15 movsd 104(%rsp), %xmm5 addq $208, %rsp jmp s5BH_info So it looks like some values are being moved from registers to the stack only to be immediately moved from the stack to the register on entry to the function. It should be possible to eliminate both the load and the stores. Is this behaviour due to LLVM or GHC? If it is GHC, it this an optimization a newcomer can attempt to implement or are there deep issues here? Jyotirmoy Bhattacharya

3 6

How to update a cabal dependency automatically
by ye yan 30 Jul '14

30 Jul '14

I have been working on a haskell scotty project recently. I have just added configuration support for the project, which added an extra dependency of Control.Lens. My question is: is there a way update .cabal file automatically, just like cabal init but without recreate .cabal file? Thanks in advance.

4 5

early adopters rejoyce! Haskell Platform 2014.2.0.0 Release Candidate 2
by Mark Lentczner 29 Jul '14

29 Jul '14

The long anticipated Haskell Platform 2014.2 release, including GHC 7.8.3, and numerous updated packages, is almost here! We have created "Release Candidate 2" installers for OS X and Windows, and believe, barring show stopper issues, creepers exploding, or unexpected trips to the nether, these will likely be blessed as the final by the end of the week. If you would like to be an early adopter, please try 'em out... - source tarball: haskell-platform-2014.2.0.0-RC2.tar.gz <http://www.ozonehouse.com/mark/platform/haskell-platform-2014.2.0.0-RC2.tar…> - source repo: haskell/haskell-platform at 2014.2.0.0-RC2 <https://github.com/haskell/haskell-platform/tree/2014.2.0.0-RC2> - windows 32bit: hskellPlatform-2014.2.0.0-i386-RC2-setup.exe <http://www.ozonehouse.com/mark/platform/hskellPlatform-2014.2.0.0-i386-RC2-…> - windows 64bit:hskellPlatform-2014.2.0.0-x86_64-RC2-setup.exe <http://www.ozonehouse.com/mark/platform/hskellPlatform-2014.2.0.0-x86_64-RC…> - os x 64bit: Haskell Platform 2014.2.0.0 64bit RC2.signed.pkg <http://www.ozonehouse.com/mark/platform/Haskell%20Platform%202014.2.0.0%206…> - travis-ci build: haskell/haskell-platform <https://travis-ci.org/haskell/haskell-platform> *Short Notes for RC2, read these if nothing else:* *General* - includes GHC 7.8.3 - includes long awaited updates to OpenGL & GLUT packages - most other packages brought up to date (or nearly so) - website is still woefully out of date... will work on it this week *Windows* *Extra thanks to Randy Polen for burning the midnight-oil to get ths out* - removed unneeded python (et al) files from the GHC bindist for 64-bit Windows (referenced in GHC ticket #9014 <https://ghc.haskell.org/trac/ghc/ticket/9014>) - added HTML "view source" pages for the GHC packages that was missing from the GHC bindist for both 32- and 64-bit Windows. *Mac OS X* *If you installed RC1 or older versions of the platform, you can remove them first with the command *sudo uninstall-hs only 7.8.3 --remove *Run it without *--remove* to see what it will do first, it if you like. You can also just install this one right on top of RC1. If you have older 7.8.3 installs from other distributions (bindist, built from src, etc...) you may want to manually remove them first... YMMV.**. Yoda says: "When doubt you have, the $PATH examine, you must!"* - works on 10.6! and 10.7, 10.8, and 10.9; with gcc or clang based Xcodes - works on 10.10!!! (Yosemite, developer preview 4 release) - works with clang out of the box, and haddock build issues with clang, fixed. *N.B.: If you have hand installed cabal 1.20, please be sure it uses Cabal 1.20.0.2 to fix the haddock issue. The platform on OS X includes cabal 1.18, using 1.18.1.4, which fixes the problem.* *Source tarball* - uses new build machinery... all the kinks may not be worked out, and not all build featuers (notably a --prefix command) are implemented yet. This doesn't affect the content of the Platform, though. - generic *nix builds, and specific distribution builds are forth coming (though feel free to chip in and help!) *Longer Notes for RC2:* *General* - Built with the new shake based build system - cgi package not included as it doesn't build under 7.8, and no word from the maintainer in quite some time - hscolour is included as a tool, mostly as it is used to build the platform itself on win and mac... but technically it isn't part of the platform - the haskell-platform package itself is not in these releases... it never contained anything other than dependencies. *Windows* - The Haskell Platform now provides a native Windows 64-bit installation (haskell-platform issue #54 <https://github.com/haskell/haskell-platform/issues/54>) - All included packages built without --enable-split-objs (GHC 7.8 FAQ <https://ghc.haskell.org/trac/ghc/wiki/GHC-7.8-FAQ#Cabal>) - All included packages built without --enable-shared (GHC ticket #8228 <https://ghc.haskell.org/trac/ghc/ticket/8228>) - If other Haskell Platform installations are detected during the installation of Haskell Platform 2014.2.0.0, a warning is displayed to the user that this is not recommended since problems will arise due to how the PATH is used in many cases to find ancillary build tools - Using ghci to build an executable that links against a DLL may result in numerous warnings about symbols (GHC ticket #9297 <https://ghc.haskell.org/trac/ghc/ticket/9297>) - The Haskell Platform for Windows, both 32-bit and 64-bit, now includes an updated version of the OpenGL Utility Toolkit (GLUT) from the FreeGLUT project, utilizing the pre-built distribution from http://www.transmissionzero.co.uk/software/freeglut-devel/ with the MinGW build (freeglut-MinGW-2.8.1-1.mp.zip). (haskell-platform issue #81 <https://github.com/haskell/haskell-platform/issues/81>) *Mac OS X* - file layout on the Mac has improved. In particular, executables are now installed directly in $prefix/bin dirs, rather than within the package dir - Distributed with a build of 7.8.3 that differs from the released bindist in two ways: a) it was built split-objs for smaller resulting executables, b) it includes Cabal-1.18.1.4 which fixes a particularly nasty problem with haddock, -XCPP, and clang based systems. This ghc-7.8.3 bindist is available as well: - ghc-7.8.3-x86_64-apple-darwin-r3.tar.bz2 <http://www.ozonehouse.com/mark/platform/ghc-7.8.3-x86_64-apple-darwin-r3.ta…> - haddocks finally cross link between packages correctly - includes a new experimental activate-hs command that can switch between multiple installed versions of the platform - includes a slightly updated uninstall-hs command - the cabal command is wrapped to provide a smoother file layout on the Mac... the wrapping only updates the ~/.cabal/config file the first time you run it.. please pay attention to its output - if you have a custom config file, you'll want to update it, as Cabal's defaults have changed *Timetable* - End of this week (from my vacation, I'll point out), we'll declare success and rename the files. — Mark *SHA-256 sums :* 62f39246ad95dd2aed6ece5138f6297f945d2b450f215d074820294310e0c48a Haskell Platform 2014.2.0.0 64bit RC2.signed.pkg 7c7d3585e89e1407461efea29dcaa9628c3be3c47d93a13b5a4978046375e4fd haskell-platform-2014.2.0.0-RC2.tar.gz 6eedd76aafb266d9a09baff80cd2973498ab59195c771f7cd64425d40be29c49 hskellPlatform-2014.2.0.0-i386-RC2-setup.exe b22115ed84d1f7e747d7f0b47e32e1489e4a24613d69c91df4ae32052f88b130 hskellPlatform-2014.2.0.0-x86_64-RC2-setup.exe

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Munich Haskell Meeting
by Heinrich Hördegen 28 Jul '14

28 Jul '14

Dear all, on Wednesday, 30th of July, once again our monthly Haskell Meeting takes place. We meet at 19h30 at Max-Emanuel-Brauerei in Munich. If you plan to join, please go here to find the details and don't forget to click the button: http://www.haskell-munich.de/dates Have a nice evening, Heinrich

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[] \\ [1..] diverges - intended?
by Niklas Hambüchen 28 Jul '14

28 Jul '14

Hi, I just noticed that import Data.List [] \\ [1..] diverges, although technically it doesn't have to (the docs suggest to me that it could just be [], and a non-diverging implementation is possible). Same for [1,2] \\ [1..] of course. Was this intended?

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New Functional Programming Job Opportunities
by Functional Jobs 28 Jul '14

28 Jul '14

Here are some functional programming job opportunities that were posted recently: Senior Haskell Developer at Plow Technologies http://functionaljobs.com/jobs/8726-senior-haskell-developer-at-plow-techno… CTO / Tech Co-Founder at Capital Match http://functionaljobs.com/jobs/8725-cto-tech-co-founder-at-capital-match Cheers, Sean Murphy FunctionalJobs.com

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Hac φ (Philadelphia): Oct 17-19, 2014
by Richard Eisenberg 28 Jul '14

28 Jul '14

Hac φ, the annual Haskell Hackathon held in Philadelphia, PA, USA, will take place Fri-Sun, Oct. 17-19, 2014. Registration is free, and all levels of Haskellers are welcome. Come join us for a weekend of programming and camaraderie. Bring your own project to work on or organize on the wiki page to join another's project. All the info, including registration link, is here: http://www.haskell.org/haskellwiki/Hac_Phi Professional Haskellers: if you work for an organization that might want to help sponsor this event, please email me. Note: This event has previously taken place during summer, but will be in October this year. Hope to see you in Philly this fall! Richard

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Problem with existential type and instance.
by Magicloud Magiclouds 28 Jul '14

28 Jul '14

Hi, For code like below, how to make it compilable? data EventHandlers = forall m. MonadIO m => EventHandlers { onDeleteWindow :: Maybe (m ()) } instance Default EventHandlers where def = EventHandlers Nothing -- 竹密岂妨流水过山高哪阻野云飞 And for G+, please use magiclouds#gmail.com.

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Retrieving information about type families
by Alejandro Serrano Mena 27 Jul '14

27 Jul '14

Dear Café, My quest for obtaining information about type families continues. Now I have a simple question: how should I access the information about "type instance"s via the GHC API? My aim is to do so after type checking, that is, to get that information from a TypecheckedModule. However, I haven't yet been able to touch the right buttons to make it work ;( Thanks in advance, Alejandro

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HTTP/2 implementation?
by Ben Bangert 26 Jul '14

26 Jul '14

Has anyone started a HTTP/2 implementation in Haskell? I see there's a HPACK-08 Haskell implementation, but I haven't seen an actual HTTP/2 impl. I've been looking at starting some work on this and didn't want to replicate effort elsewhere that I may have missed. Cheers, Ben

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ANNOUNCE: hplayground: haskell client-side web framework
by Alberto G. Corona 26 Jul '14

26 Jul '14

hplayground [1] is a haskell framework that compiles to JavaScript with the haste [5] compiler. It handles reactive effects under a applicative-monad that controls the modifications of the user interface. It is quite easy to create dynamic, composable applications using ordinary, beatiful, idiomatic haskell without special constructions. Rather than a framework, it is an EDSL. Full reinversion of control avoid spagetty event handlers and the monad confines the events and their effects to the subtree where they appear avoiding the problems of declarative reactive frameworks. There are examples running[4] the source code is in [1] And there is a todo reference application [3] running [2] too. There is also a blog post about that[7] Additionally, the syntax is almost identical to the formlet widgets in MFlow[6]. So most of the hplaygroud code could run also in a server if javascript is disabled. But MFlow and hplayground are completely independent projects. I hope that you enjoy it as much as I enjoyed the development of it. A big thanks to Anton Ekblad for his wonderful Haste compiler. [1] https://github.com/agocorona/hplayground [2] http://mflowdemo.herokuapp.com/todo.html [3] https://github.com/agocorona/hplay-todo [4] http://mflowdemo.herokuapp.com/noscript/wiki/browserwidgets [5] http://http://haste-lang.org/ [6] http://hackage.haskell.org/package/MFlow [7] http://haskell-web.blogspot.com.es/2014/07/hplayground-translate-your-conso… -- Alberto.

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support request
by Закиров Марат 25 Jul '14

25 Jul '14

Hi All! I need to convince group of managers that Haskell is cool. Could you please share some links, presentations, data and maybe experience? Thanks in advance... -- Regards, Marat. С уважением Марат.

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callCC inside expression
by martin 25 Jul '14

25 Jul '14

Hello all I recently saw a video on call/cc in Scheme, where call/cc was used inside an expression and call/cc faithfully figured out the rest of the computation. I tried the same in haskell, but was bitten badly. Then I looked at the type signature and learned that call/cc only works inside a continuation monad (if I am not mistaken). Is this correct and why is that so? Are scheme's call/cc and haskell's callCC semantically different?

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what is basic Haskell?
by Johan Larson 25 Jul '14

25 Jul '14

What does a programmer need to know to be proficient in "basic Haskell"? For my money, basic programming skills are those that are required to write programs for simple tasks in the common idioms of the language. This means the practitioner should be able to read input from the terminal or files, select/combine/reformat data, and output a result. At this point, efficiency isn't really the point; only getting to a correct answer without writing anything really weird matters. In LYAH, I'd put the boundary at the end of chapter 9, which covers the IO monad. At that point the reader has studied functions, lists, tuples, types, recursion, higher order functions, four major modules, and algebraic data types. Actually, some of the later topics in chapter 8 (functors, kinds, recursive data structures) seem more like intermediate material. Thoughts? -- Johan Larson -- Toronto, Canada

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Markov Text Generator & Randomness
by Charles-Pierre Astolfi 24 Jul '14

24 Jul '14

Hi -cafe, I'm coding a Markov Text Generator (of order 1). Basically, you have a source text, and knowing the frequencies of pairs of consecutive words, you generate a somewhat syntactically correct text from this. Here's the link to my code and to a source text you can use as example. test.txt http://lpaste.net/raw/4004174907431714816 code http://lpaste.net/4147715261379641344 The kickers is that this code generates sentences with consecutive words that never appears next to each other in the source text. For example, the code generated "They sat over at because old those the lighted.", but "over at" never occurs in the source text, so it shouldn't occur in a generated sentence. The makeDb function gives is correct, so my problem actually lies in generate and/or in draw. I think there's something about RVar that I messed up, but I don't see the problem. Any ideas? Cheers, -- Charles-Pierre

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Haskell on JVM (using LLVM backend)
by Wojciech Danilo 24 Jul '14

24 Jul '14

Hello! I was recently discussing with some frients possibilities of running Haskell programs on JVM. I belive such possibility could be a breakdown for the popularity of Haskell and could be very interesting for new people and new usage-scenarios. I have seen some topics, like these: http://stackoverflow.com/questions/7261039/haskell-on-jvm http://www.haskell.org/haskellwiki/GHC/FAQ#Why_isn.27t_GHC_available_for_.N… http://www.haskell.org/pipermail/haskell-cafe/2009-June/063454.html but are a little old and do NOT mention the LLVM backend. If we've got the LLVM backend in GHC right now, why cannot we just use something like LLJVM to convert the LLVMIR into JVM bytecode? I understand that the LLVM bytecode (optained from GHC) has all the optimizations applied (including tail recursion expansion) so it **could** be possible to just run it on JVM? All the best, Wojciech Daniło

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Re: [Haskell-cafe] determining the origin of imported symbols
by Erik Rantapaa 24 Jul '14

24 Jul '14

Thanks, everyone, for all of the suggestions! On Thursday, July 24, 2014 5:53:59 AM UTC-5, Eyal Lotem wrote: > > There's also ghc's -ddump-minimal-imports which might help you. > > > On Thu, Jul 24, 2014 at 12:06 PM, JP Moresmau <jpmor...(a)gmail.com > <javascript:>> wrote: > >> BuildWrapper doesn't do the transformation, but it resolves all symbols >> to build a usage map, so it would tell you that Data.List.sort is used at >> line xxx, using the GHC API. So have a look at around >> https://github.com/JPMoresmau/BuildWrapper/blob/master/src/Language/Haskell…. >> BuildWrapper takes the GHC AST, transforms it into a JSON structure, and >> extracts all usage information. There is also an import reorganization >> function that may be useful. >> >> JP >> >> >> On Thu, Jul 24, 2014 at 10:29 AM, Erik Rantapaa <eran...(a)gmail.com >> <javascript:>> wrote: >> >>> Hi everyone, >>> >>> I looking for a way to analyze Haskell source to determine which module >>> each imported symbol comes from. My goal is to transform source code like >>> this: >>> >>> import Data.List >>> ... >>> main = do >>> nums <- fmap (map read . words) getLine :: IO [Int] >>> print $ sort nums >>> >>> to code like this: >>> >>> import qualified Prelude as B >>> import qualified Data.List as A >>> ... >>> main = do >>> nums <- B.fmap (B.map B.read B.. B.words) B.getLine :: B.IO >>> [B.Int] >>> B.print B.$ A.sort nums >>> >>> That is, I want to qualify all imported symbols with a module alias. >>> >>> Can anyone suggest modules or programs I should look at? >>> >>> Thanks, >>> ER >>> >>> _______________________________________________ >>> Haskell-Cafe mailing list >>> Haskel...(a)haskell.org <javascript:> >>> http://www.haskell.org/mailman/listinfo/haskell-cafe >>> >>> >> >> >> -- >> JP Moresmau >> http://jpmoresmau.blogspot.com/ >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Haskell-cafe" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to haskell-cafe...(a)googlegroups.com <javascript:>. >> To post to this group, send email to haskel...(a)googlegroups.com >> <javascript:>. >> Visit this group at http://groups.google.com/group/haskell-cafe. >> For more options, visit https://groups.google.com/d/optout. >> > > > > -- > Eyal >

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determining the origin of imported symbols
by Erik Rantapaa 24 Jul '14

24 Jul '14

Hi everyone, I looking for a way to analyze Haskell source to determine which module each imported symbol comes from. My goal is to transform source code like this: import Data.List ... main = do nums <- fmap (map read . words) getLine :: IO [Int] print $ sort nums to code like this: import qualified Prelude as B import qualified Data.List as A ... main = do nums <- B.fmap (B.map B.read B.. B.words) B.getLine :: B.IO [B.Int] B.print B.$ A.sort nums That is, I want to qualify all imported symbols with a module alias. Can anyone suggest modules or programs I should look at? Thanks, ER

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OverlappingInstances-extension-like for type families
by Leza Morais Lutonda 23 Jul '14

23 Jul '14

Hello haskell-café, I just started working with type families, and come with some difficulties. Now I have a class: class (...) ⇒ Complexable s where type ComplexSignalType s ... Is there a possibility to have this two instances (in any way)? instance (RealFloat e) ⇒ Complexable [e] where type ComplexSignalType [e] = [ℂ e] instance (RealFloat e) ⇒ Complexable [ℂ e] where type ComplexSignalType [ℂ e] = [ℂ e] Thanks. -- Leza Morais Lutonda, Lemol-C http://lemol.github.io 50 Aniversario de la Cujae. Inaugurada por Fidel el 2 de diciembre de 1964 http://cujae.edu.cu

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How many Haskell programmers are there?
by Johan Larson 23 Jul '14

23 Jul '14

Obviously this is a very fuzzy question. But what's the credible range of answers? Here's one: http://steve-yegge.blogspot.ca/2010/12/haskell-researchers-announce-discove… 38 -- Johan Larson -- Toronto, Canada

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Looking for list comprehensions use cases
by Jan Stolarek 23 Jul '14

23 Jul '14

Haskellers, recently I've been looking into the possibility of creating some new optimisations for GHC. These would be mostly aimed at list comprehensions. Here's where I need your help: 1. Do you have complex list comprehensions usage examples from real code? By complex I mean nested list comprehensions, reading from more than one list ([ ...| x <- xs, y <- ys ... ]) etc. 2. Do you have list comprehensions code that you had to optimize by hand because GHC was unable to make them fast enough? Janek

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Call for participation: Haskell tutorial at CUFP on 4 Sep 2014
by Stefan Wehr 22 Jul '14

22 Jul '14

Dear Haskellers, I'll be giving an advanced Haskell tutorial as part of the CUFP 2014 workshop. * Date/time: 4 Sep 2014, 9:00 AM - 12:30 PM * Place: Gothenburg, Sweden (affiliated with ICFP 2014) * Early registration deadline: 3 Aug 2014! The tutorial teaches important techniques for writing correct, robust, scalable, and fast Haskell programs. The topics covered are: network programming, serialization, persistence, logging, performance, scalability, testing, and concurrency. The tutorial aims at programmers with some Haskell experience. It is not necessary to be an Haskell expert, but you should know how to write functions and data types. For more details, see http://cufp.org/2014/t2-stefan-wehr-haskell-in-the-real-world.html Registration page: https://regmaster4.com/2014conf/ICFP14/register.php Please distribute this call for participation. See you in Gothenburg! Stefan

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Elementary algorithms - (Haskell language is used)
by Xinyu LIU 22 Jul '14

22 Jul '14

Hi, I spent 6 years to write the book ‘Elementary Algorithms’. I finally completed it yesterday. This book is open and free, the PDF version can be downloaded from: https://github.com/liuxinyu95/AlgoXY/blob/algoxy/preview/elementary-algorit… Why There are plenty of books about algorithms, such as ‘Introduction to algorithms’, ‘The art of computer programming’, ‘structure and interpretation of computer programs’… why another book? Is it reinvention of wheel? This book can’t compare with the above classic bibles at all. It has some features like: 1. All algorithms are described in math formulas and pseudo codes. I hope it bring some taste of elegant by using algebraic symbols. 2. All algorithms are realized in both purely functional and imperative approaches. 3. The examples are provided in multiple programming languages, including C, Haskell, Python, C++, Scheme/Lisp. Haskell is the main language for all functional implementations. Content The following content are covered in this book (in the order of appearance) • Binary search tree, insertion sort, red-black tree, AVL tree, Trie, Patricia, suffix tree, B-tree; • Binary heap, Leftist heap, skew heap, splay heap, selection sort, binomial heap, Fibonacci heap, pairing heap; • Queue, Finger tree based sequence, quick sort, merge sort, binary search, saddle-back search, KMP, Boyer-Moore, DFS, BFS, Greedy algorithm, Dynamic programming. There are two books influenced me most, one is ‘Purely functional data structure’ by Chris Okasaki, the other is ‘Introduction to algorithms’. Problems I always don’t have enough time in writing this book during the past 6 years. I am not a native speaker, the biggest problem is about English. It is lack of proof reading by native speakers. I used some result directly, if I had time, I should add more proof for those results. Future work Ideally, I think a serious algorithm book should be written in a stable environment. I planned to write this book in 10 years. But everything changes so fast in modern society. I experienced lay-offs once in 2012 due to Symbian business cut off, and now again in MS. I am not sure if I can continue this work. I think the best way is to open this book to the community. Some future work in my mind: • Proof reading and review • Provide answers to the exercises • Provide proof for the directly referenced result The whole manuscript is available at github: https://github.com/liuxinyu95/AlgoXY Best regards -- Larry, LIU Xinyu https://sites.google.com/site/algoxy/ https://github.com/liuxinyu95/AlgoXY *e*^(*π*i)+1 = 0

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GHCI on ARM (Nvidia Jetson TK1)
by Tomas Korcak 21 Jul '14

21 Jul '14

Hi There, I would like to ask you what is the situation with ghci on arm. I bought Jetson TK1 and I am really sad that ghci does not works there. I have found mentioned somewhere that this should be fixed in 7.4.2 but still it is not. Can somebody clarify what is the situation at the moment and what are further plans? Best regards, T. -- <warning> This e-mail is intended for the named recipient(s). It may contain privileged and/or confidential information. If you are not one of the intended recipients, please notify the sender immediately and destroy this e-mail and attachment(s): you must not copy, distribute, retain or take any action in reliance upon the email or attachment(s). While all reasonable efforts are made to safeguard inbound and outbound e-mails, Tomas Korcak cannot guarantee that attachments are virus-free or are compatible with your systems, and does not accept liability in respect of viruses or computer problems experienced. Thank you. </warning> <notice> Your Skills In Reading Have Improved +1 </notice> <idea> Some days you're the dog; some days you're the hydrant. </idea>

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What is the state of the art in testing code generation?
by oleg＠okmij.org 21 Jul '14

21 Jul '14

Tom Ellis wrote: > The first impediment to using QuickCheck is that my EDSL is typed. I don't > know how to generate random terms in the presence of types. First I should point out Magic Haskeller (which generates typed (Haskell) terms and then accepts those that satisfy the given input-output relationship). http://nautilus.cs.miyazaki-u.ac.jp/~skata/MagicHaskeller.html It is MagicHaskeller on Hackage. The most straightforward method is to generate random terms and filter well-typed ones. This is usually a bad method since many or most randomly generated terms will be ill-typed. One should generate well-typed terms from the beginning, without any rejections. That is actually not difficult: one merely needs to take the type checker (which one has to write anyway) and run it backwards. Perhaps it is not as simple as I made it sound, depending on the type system (for example, the type inference for simply-typed lambda-calculus without any annotations requires guessing. One has to guess correctly all the type, otherwise the process becomes slow). It has been done, in a mainstream functional language: OCaml. The code can be re-written for Haskell using the tricks for non-determinism with sharing (the Share monad). Due to many deadlines I cannot re-write myself, not until the middle of the next week. Also, I don't know your type system. If you are curious about the OCaml code, it can be found at http://okmij.org/ftp/kakuritu/type_inference.ml The main function is let rec typeof : gamma -> term -> tp = fun gamma exp -> match exp () with | I _ -> int | V name -> begin try List.assoc name gamma with Not_found -> fail () end | L (v,body) -> let targ = new_tvar() in let tbody = typeof ((v,targ) :: gamma) body in arr targ tbody | A (e1,e2) -> let tres = new_tvar() in tp_same (typeof gamma e1) (arr (typeof gamma e2) tres); tres It can infer a type of a term (or fail if it is will-typed), it can generate well-typed terms one-by-one, or it can generate all terms of a particular structure (e.g., with two lambdas at the top) and/or of a particular type or type shape (e.g., an arrow).

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