- Haskell-Cafe - Haskell.org

Trying to install hpodder on OS X Lion
by seanh 21 Oct '11

21 Oct '11

I'd really like to get hpodder installed on OS X Lion, I can't find it packaged anywhere (macports, homebrew...) Has anyone got it working? I have the haskell platform installed from the pkg file from haskell.org: http://hackage.haskell.org/platform/mac.html So I tried `cabal install hpodder` but it failed. First I get a lot of warnings like: ld: warning: text reloc in _cZh_str to _stg_ap_pppppp_fast ld: warning: text reloc in _cZh_str to _stg_ap_ppppp_fast ld: warning: text reloc in _cZh_str to _stg_ap_pppp_fast ld: warning: text reloc in _cZh_str to _stg_ap_pppv_fast ld: warning: text reloc in _cZh_str to _stg_ap_ppp_fast ld: warning: text reloc in _cZh_str to _stg_ap_ppv_fast ld: warning: text reloc in _cZh_str to _stg_ap_pp_fast ld: warning: text reloc in _cZh_str to _stg_ap_pv_fast ld: warning: text reloc in _cZh_str to _stg_ap_p_fast ld: warning: text reloc in _cZh_str to _stg_ap_n_fast ld: warning: text reloc in _cZh_str to _stg_ap_l_fast ld: warning: text reloc in _cZh_str to _stg_ap_d_fast ld: warning: text reloc in _cZh_str to _stg_ap_f_fast ld: warning: text reloc in _cZh_str to _stg_ap_v_fast ld: warning: text reloc in _cZh_str to _stg_ap_pppppp_info I get each of those warnings many times in a row. There are some other warning when compiling things as well. Then I eventually get: cabal: Error: some packages failed to install: hpodder-1.1.5 failed during the building phase. The exception was: ExitFailure 1 Here's the error from the compiler before that: Commands/SetStatus.hs:59:33: Ambiguous type variable `e0' in the constraint: (E.Exception e0) arising from a use of `E.catch' Probable fix: add a type signature that fixes these type variable(s) In the expression: E.catch (E.evaluate (read x)) (\ _ -> fail $ "Invalid status supplied; use one of: " ++ possibleStatuses) In a case alternative: Just x -> E.catch (E.evaluate (read x)) (\ _ -> fail $ "Invalid status supplied; use one of: " ++ possibleStatuses) In a stmt of a 'do' expression: newstatus <- case lookup "status" args of { Just x -> E.catch (E.evaluate (read x)) (\ _ -> fail $ "Invalid status supplied; use one of: " ++ possibleStatuses) Nothing -> fail "setstatus: --status required; see hpodder setstatus --help" }

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Functional Programmer required for a Greenfield project in a software house in London.
by Oliver Horncastle 21 Oct '11

21 Oct '11

Ideally from a high performance computing, real-time systems background (OO experience, either java or c++). Get in touch for more details. Oliver Horncastle Madison Maclean Email: Oliver.horncastle(a)madisonmaclean.com<mailto:Oliver.horncastle@madisonmaclean.com> Direct Line: 020 30 30 50 53

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Betfair Opportunity
by James Peters 21 Oct '11

21 Oct '11

Hello, I currently work internally at Betfair and we seek Haskell specialists to join our research teams on a permanent basis in London. Please contact me for more details. Thanks, James C Peters Senior Research and Sourcing Consultant Office: +44 (0) 208 834 8513 http://uk.linkedin.com/in/jamescpeters Check out the Betfair Employee Blog: Betfair views | Home of Betfair's Employee Blog<http://views.betfair.com/> Betfair The #1 Global Online Sports Betting Operator. Please consider the environment before printing this e-mail. Betfair Limited | Winslow Road | Hammersmith Embankment | London | W6 9HP. Registered in England and Wales under company number 5140986. This email (which includes any attachment and any subsequent reply) is sent for and on behalf of one or more operating entities in the Betfair Group, details of which are available here<http://corporate.betfair.com/about-us.aspx>. The information in this e-mail is confidential and may contain legal advice that is subject to legal privilege. As such it is intended only for the named recipient(s). This e-mail may not be disclosed or used by any person other than the addressee, nor may it be copied in any way. If you are not a named recipient please notify the sender immediately and delete any copies of this email. Any unauthorised copying, disclosure or distribution of the material in this e-mail is strictly forbidden. Any view or opinions presented are solely those of the author and do not necessarily represent those of the Betfair Group. Betfair(r) and the BETFAIR LOGO are registered trade marks of The Sporting Exchange Limited. ________________________________________________________________________ In order to protect our email recipients, Betfair Group use SkyScan from MessageLabs to scan all Incoming and Outgoing mail for viruses. ________________________________________________________________________

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Re: [Haskell-cafe] ANN: OpenCL 1.0.1.3 package
by Luis Cabellos 21 Oct '11

21 Oct '11

On Thu, Oct 13, 2011 at 9:13 PM, Martin Dybdal <dybber(a)dybber.dk> wrote: > Hi everyone > > I just found this thread today, as I don't read Haskell-cafe that > often (too bad, I know). I have been working on a set of OpenCL > bindings for the last months myself, which I'm using to implement an > OpenCL backend to the Data.Array.Accelerate library. The work is done > at the HIPERFIT research center, Uni. Copenhagen. > > My bindings are even further from the naming conventions of the OpenCL > library, but I really can't see the problem with that. People which > are used to programming OpenCL from C/C++ might have to learn how the > naming conventions of the Haskell library are, but they only need to > do this once. When the mapping between the old and the new naming > conventions are learned, they will benefit from having a more clean > interface for all future times. (No Haskell hacker should have a > problem with a steep learning curve.) I'll just add, haddock + hoogle has done a lot remove the learn all names necessity. > It is somewhat troubling that we now have five different interfaces to > OpenCL (that I know of), and I think we should join efforts and make > one library that is as stable as possible. The five libraries are: > > * OpenCL > * OpenCLRaw > * HsOpenCL > * hopencl > * The library presented by Benedict Gaster at AMD (yet to be released) > ( http://developer.amd.com/zones/OpenCLZone/publications/assets/MakingOpenCLS… > ) * OpenCLRaw for me is a dead one. The main developer make no reply. * OpenCL, HsOpenCL and hopencl are the packages more suitable tu fuse. I think that the best aproach is to use the OpenCL standard API as it is, and let more libraries that use *opencl* packages decide what high-level API offer. I like the Accelerate approach to show a better API to users. I currently working in the application that need the use of OpenCL. The package that I develop offers all I need for now, so I not upgrading it, only bugs or requested features for users. But in the future I plan for two options: a) change to the *opencl* package that gets mainstream, or b) continue with own OpenCL package because it feels ok. > My own library is available at https://github.com/HIPERFIT/hopencl and > will be released on hackage very soon (next week probably). Please > take a look at it. It is currently tested on x86_64 Linux with both > the AMD x86/x86_64 bindings and NVIDIAs CUDA bindings. They will > probably not work on Windows in their present state, and I don't have > access to a Windows machine to test it on. As Jason Dagit say, I put the stdcall call convention option in OpenCL for windows: https://github.com/zhensydow/opencl/blob/master/OpenCL.cabal Other issues to solve, How to compile in hackage server to generate documentation online? opencl.h isn't in the server so I getting errors. > > -- > Martin Dybdal >

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ANNOUNCE: vector-bytestring-0.0.0.0
by Bas van Dijk 21 Oct '11

21 Oct '11

All your ByteString are belong to us... Hello, I'm pleased to announce the beta release of vector-bytestring. This library provides the type ByteString which is defined as a type synonym for a storable Vector of Word8s (from the vector package): type ByteString = Data.Vector.Storable.Vector Word8 It exports the same API as the bytestring package except that the module names are prefixed with: Data.Vector.Storable.ByteString instead of Data.ByteString. The very ambitious goal of this package is that it will eventually replace our beloved bytestring package. By basing this package on vector, we can benefit from all the optimizations (like stream-fusion!) in that library. We will also have just a single library to test, debug and optimize. TEST-SUITE I ported the bytestring test-suite to vector-bytestring. You can run it using: $ cabal configure --enable-tests; cabal build; cabal test All 54800 tests pass! Only one property doesn't hold: prop_show :: ByteString -> Bool prop_show x = show x == show (unpack x) This is because I don't provide a custom Show instance for ByteStrings but use the one from Vector which shows a vector like "fromList [1,2,3]" instead as "\SOH\STX\ETX" like bytestring does. Hopefully this is not a problem in practice. BENCHMARKS I added a criterion based benchmark-suite to vector-bytestring. It consists of over 600 benchmarks that cover almost every function in the library. Also included are benchmarks which benchmark the fusion capabilities of the library. Run it using: $ cabal configure -fbenchmark; cabal build; $ dist/build/bench/bench --help Unfortunately, bytestring still out performs us in lots of benchmarks. I believe the primary cause of this is that most functions are implemented using stream-fusion. This is highly efficient if you use a composition of these functions because they will all fuse into one single efficient loop. However if your program uses only a single function, the stream based implementation is often less efficient than an implementation that works directly on a mutable vector (like most functions in bytestring). So what we want is to use stream-fusion where possible but use mutable vectors when our program doesn't fuse. Fortunately, Roman Leshchinskiy (author of vector) has an idea how to do this: http://trac.haskell.org/vector/ticket/60 Because we don't beat bytestring in all cases yet you should consider this a beta-release and not use it in production code. INSTALLING $ cabal install vector-bytestring API DOCS http://hackage.haskell.org/package/vector-bytestring-0.0.0.0 DEVELOPING $ git clone https://github.com/basvandijk/vector-bytestring Regards, Bas

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Type constructor variables no longer injective in GHC 7.2.1?
by Daniel Schüssler 21 Oct '11

21 Oct '11

Hello Cafe, say we take these standard definitions: > {-# LANGUAGE GADTs, TypeOperators, TypeFamilies, ScopedTypeVariables #-} > data a :=: b where > Refl :: a :=: a > subst :: a :=: b -> f a -> f b > subst Refl = id Then this doesn't work (error message at the bottom): > inj1 :: forall f a b. f a :=: f b -> a :=: b > inj1 Refl = Refl But one can still construct it with a trick that Oleg used in the context of Leibniz equality: > type family Arg fa > type instance Arg (f a) = a > newtype Helper fa fa' = Helper { runHelper :: Arg fa :=: Arg fa' } > inj2 :: forall f a b. f a :=: f b -> a :=: b > inj2 p = runHelper (subst p (Helper Refl :: Helper (f a) (f a))) So, it seems to me that either rejecting inj1 is a bug (or at least an inconvenience), or GHC is for some reason justified in not assuming type constructor variables to be injective, and accepting inj2 is a bug. I guess it's the former, since type constructor variables can't range over type functions AFAIK. The error message for inj1 is: Could not deduce (a ~ b) from the context (f a ~ f b) bound by a pattern with constructor Refl :: forall a. a :=: a, in an equation for `inj1' at /tmp/inj.lhs:12:8-11 `a' is a rigid type variable bound by the type signature for inj1 :: (f a :=: f b) -> a :=: b at /tmp/inj.lhs:12:3 `b' is a rigid type variable bound by the type signature for inj1 :: (f a :=: f b) -> a :=: b at /tmp/inj.lhs:12:3 Expected type: a :=: b Actual type: a :=: a In the expression: Refl In an equation for `inj1': inj1 Refl = Refl Cheers, Daniel

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ICFP 2012: Call for workshops and co-located events
by Wouter Swierstra 21 Oct '11

21 Oct '11

CALL FOR WORKSHOP AND CO-LOCATED EVENT PROPOSALS ICFP 2012 17th ACM SIGPLAN International Conference on Functional Programming September 9 - 15, 2012 Copenhagen, Denmark http://icfpconference.org/icfp2012/ The 17th ACM SIGPLAN International Conference on Functional Programming will be held in Copenhagen, Denmark on September 9-15, 2012. ICFP provides a forum for researchers and developers to hear about the latest work on the design, implementations, principles, and uses of functional programming. Proposals are invited for workshops (and other co-located events, such as tutorials) to be affiliated with ICFP 2012 and sponsored by SIGPLAN. These events should be more informal and focused than ICFP itself, include sessions that enable interaction among the attendees, and foster the exchange of new ideas. The preference is for one-day events, but other schedules can also be considered. The workshops are scheduled to occur on September 9 (the day before ICFP) and September 13-15 (the three days after ICFP). ---------------------------------------------------------------------- Submission details Deadline for submission: November 19, 2011 Notification of acceptance: December 17, 2011 Prospective organizers of workshops or other co-located events are invited to submit a completed workshop proposal form in plain text format to the ICFP 2012 workshop co-chairs (Patrik Jansson and Gabriele Keller), via email to icfp12-workshops at cse.unsw.edu.au by November 19, 2011. (For proposals of co-located events other than workshops, please fill in the workshop proposal form and just leave blank any sections that do not apply.) Please note that this is a firm deadline. Organizers will be notified if their event proposal is accepted by December 17, 2011, and if successful, depending on the event, they will be asked to produce a final report after the event has taken place that is suitable for publication in SIGPLAN Notices. The proposal form is available at: http://www.icfpconference.org/icfp2012/icfp12-workshops-form.txt Further information about SIGPLAN sponsorship is available at: http://acm.org/sigplan/sigplan_workshop_proposal.htm ---------------------------------------------------------------------- Selection committee The proposals will be evaluated by a committee comprising the following members of the ICFP 2012 organizing committee, together with the members of the SIGPLAN executive committee. Workshop Co-Chair: Gabriele Keller (University of New South Wales) Workshop Co-Chair: Patrik Jansson (Chalmers University of Technology) General Chair : Peter Thiemann (University of Freiburg) Program Chair: Robby Findler (Northwestern University) ---------------------------------------------------------------------- Further information Any queries should be addressed to the workshop co-chairs (Patrik Jansson and Gabriele Keller), via email to icfp12-workshops at cse.unsw.edu.au

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Re: [Haskell-cafe] How to implement a digital filter, using Arrows?
by Captain Freako 20 Oct '11

20 Oct '11

John Lask wrote: >This is literate code. It expounds on your initial question and provides >two solutions based either on the StateArrow or Automaton.... >(Remainder omitted.) John, Thanks so much for your help! I'm going to study your example code and try to understand how the Automaton implicit plumbing is being used. (I'm determined to get my head around this arrow concept, damn it! ;-) ) I wonder if I might pester you for the final piece of the puzzle here: When the processing of the input stream through the filter is complete, I need to pass the final filter state, along with the output stream, back to the calling program. (This is because the calling program is going to split the input signal into conveniently sized chunks, calling my filter routine several times, in order to process the entire input stream. It expects to be able to pass an initial filter state into my routine, which is just the final state of the filter that I passed back to it after the previous call. In this way, we avoid inserting any edge artifacts at the input stream segmentation boundaries.) So, is it possible to `fetch' the final state out of that Automaton, when it's finished processing the input list? Thanks! -db

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Implementing a New primop
by Paul Monday 20 Oct '11

20 Oct '11

Alright, I wandered through some primtype issues, but I'm having another odd problem as I try to define my own primop. I've followed what the various wiki pages have to offer (primarily http://hackage.haskell.org/trac/ghc/wiki/AddingNewPrimitiveOperations and http://hackage.haskell.org/trac/ghc/wiki/Commentary/PrimOps) without success. I even unraveled my PrimOp to be, basically, an exact copy of another PrimOp without luck. The primop I'm attempting to add is now very, very simple and copies FloatAddOp exactly so there must be an additional file I have to modify before the primop is "completely" added. ./compiler/prelude/primops.txt.pp primop FloatVAddOp "plusFloatVec#" Dyadic Float# -> Float# -> Float# with commutable = True ./compiler/codeGen/CgPrimOp.hs translateOp FloatVAddOp = Just (MO_F_Add W32) The compiler error is below. I have the feeling that an interface is not being built somewhere … this must be a simple one but I can't find any references to this error anywhere … has anyone seen this one before????? "inplace/bin/ghc-stage1" -H64m -O0 -fasm -package-name ghc-7.3.20111007 -hide-all-packages -i -icompiler/basicTypes -icompiler/cmm -icompiler/codeGen -icompiler/coreSyn -icompiler/deSugar -icompiler/ghci -icompiler/hsSyn -icompiler/iface -icompiler/llvmGen -icompiler/main -icompiler/nativeGen -icompiler/parser -icompiler/prelude -icompiler/profiling -icompiler/rename -icompiler/simplCore -icompiler/simplStg -icompiler/specialise -icompiler/stgSyn -icompiler/stranal -icompiler/typecheck -icompiler/types -icompiler/utils -icompiler/vectorise -icompiler/stage2/build -icompiler/stage2/build/autogen -Icompiler/stage2/build -Icompiler/stage2/build/autogen -Icompiler/../libffi/build/include -Icompiler/stage2 -Icompiler/../libraries/base/cbits -Icompiler/../libraries/base/include -Icompiler/. -Icompiler/parser -Icompiler/utils -optP-DGHCI -optP-include -optPcompiler/stage2/build/autogen/cabal_macros.h -package Cabal-1.11.2 -package array-0.3.0.3 -package base-4.4.0.0 -package bin-package-db-0.0.0.0 -package bytestring-0.9.2.0 -package containers-0.4.2.0 -package directory-1.1.0.1 -package filepath-1.2.0.1 -package hoopl-3.8.7.2 -package hpc-0.5.1.0 -package old-time-1.0.0.7 -package process-1.1.0.0 -package template-haskell-2.6.0.0 -package unix-2.5.0.0 -Wall -fno-warn-name-shadowing -fno-warn-orphans -XHaskell98 -XNondecreasingIndentation -XCPP -XMagicHash -XUnboxedTuples -XPatternGuards -XForeignFunctionInterface -XEmptyDataDecls -XTypeSynonymInstances -XMultiParamTypeClasses -XFlexibleInstances -XRank2Types -XScopedTypeVariables -XDeriveDataTypeable -DGHCI_TABLES_NEXT_TO_CODE -DSTAGE=2 -O0 -fasm -no-user-package-conf -rtsopts -odir compiler/stage2/build -hidir compiler/stage2/build -stubdir compiler/stage2/build -hisuf hi -osuf o -hcsuf hc -c compiler/iface/BinIface.hs -o compiler/stage2/build/BinIface.o ghc-stage1: panic! (the 'impossible' happened) (GHC version 7.3.20111007 for x86_64-unknown-linux): applyTypeToArgs ghc-prim:GHC.Prim.sizeofMutableArray#{(w) v 91V} [gid[PrimOp]] @ e{tv i4L2} [tv] ds{v i4Lc} [lid] i#{v i4Lg} [lid] forall a{tv 12} [tv]. ghc-prim:GHC.Prim.MutableArray#{(w) tc 31m} e{tv i4L2} [tv] a{tv 12} [tv] -> ghc-prim:GHC.Prim.Int#{(w) tc 3G} Paul Monday Parallel Scientific, LLC. paul.monday(a)parsci.com

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Online tutorial about Heist, Mvars, Anansi
by nadine.and.henry＠pobox.com 20 Oct '11

20 Oct '11

Dear haskellers, I've spent the last few days scratching my head and wading through heist code. The result of my efforts is a tutorial available at: http://www.nadineloveshenry.com/haskell/heistTutorial.html Any corrections, suggestions, compliments or misc. personal abuse are always welcome. Best wishes, Henry -- Nadine & Henry Laxen Belle, Venus, Aphrodite 10580 N. McCarran Blvd. Adonis, Jarod Suite 115-396 Via Alta # 6 Reno, Nevada Chapala, Jalisco, Mexico 89503-1896 CP 45900 http://www.nadineloveshenry.com/ The rest is silence. (Hamlet)

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Haskell Weekly News: Issue 204
by Daniel Santa Cruz 20 Oct '11

20 Oct '11

Welcome to issue 204 of the HWN, a newsletter covering developments in the Haskell community. This release covers the week of October 9 to 15, 2011. You can find the HTML version of this issue at: http://contemplatecode.blogspot.com/2011/10/haskell-weekly-news-issue-204.h… New and Updated Projects * lhs2tex-hl (Alessandro Vermeulen; 1.4.3) Upgraded package builds with GHC 7.2.x. [1] http://goo.gl/2VQmw * global-variables (Jean-Marie Gaillourdet; 1.0) A package providing a global namespace for IORefs, MVars, and TVars. [2] http://goo.gl/B9YPO * vector-bytestring (Bas van Dijk; 0.0.0.0) "The very ambitious goal of this package is that it will eventually replace our beloved bytestring package. By basing this package on vector, we can benefit from all the optimizations (like stream-fusion!) in that library." [3] http://goo.gl/SAUiF * simple-actors (Brandon Simmons; 0.1.0) An eDSL library for actor model concurrency. [4] http://goo.gl/f9hvu * ircbot (Jeremy Shaw; 0.1.1) ... "becase that's what Haskell really needs -- another irc bot library." [5] http://goo.gl/A252O Quotes of the Week * Pseudonym: A type is a collection of values, and a class is a collection of types. * xplat: you just need to write a corresponding set of modules for well-hung coinduction * Porges: State is stored in spacesuits. [via: reddit] [djahandarie] Group projects are stupid [shachaf] Try a semigroup project sometime. You need to lose your identity. Top Reddit Stories * shqq: Embedding shell commands in Haskell code Domain: mainisusuallyafunction.blogspot.com, Score: 51, Comments: 5 On Reddit: [6] http://goo.gl/b7zj5 Original: [7] http://goo.gl/9LVhi * Shooting yourself in the foot with Haskell Domain: haskell.org, Score: 47, Comments: 7 On Reddit: [8] http://goo.gl/C1VJY Original: [9] http://goo.gl/yGceC * Why learn Haskell? [PDF slides] Domain: ugcs.net, Score: 32, Comments: 31 On Reddit: [10] http://goo.gl/Coml0 Original: [11] http://goo.gl/MgVwe * How to beat the CAP theorem - purely functional databases Domain: nathanmarz.com, Score: 28, Comments: 11 On Reddit: [12] http://goo.gl/s1TjI Original: [13] http://goo.gl/HQvlK * Yo /r/haskell, I heard you like monads... Domain: self.haskell, Score: 25, Comments: 26 On Reddit: [14] http://goo.gl/xSbj7 Original: [15] http://goo.gl/xSbj7 * FRP and Haskell being used for physiological experimentation and analysis - Haskell-cafe Domain: haskell.org, Score: 21, Comments: 3 On Reddit: [16] http://goo.gl/XxE3y Original: [17] http://goo.gl/fMBMR * Composing a list of Enumeratees Domain: permalink.gmane.org, Score: 19, Comments: 14 On Reddit: [18] http://goo.gl/fwcY1 Original: [19] http://goo.gl/V2bgc * hp2pretty-0.5 released - Now with go faster stripes! Domain: claudiusmaximus.goto10.org, Score: 19, Comments: 0 On Reddit: [20] http://goo.gl/csnhI Original: [21] http://goo.gl/18myY * FRP - How to deal with concurrent external events? Domain: apfelmus.nfshost.com, Score: 16, Comments: 0 On Reddit: [22] http://goo.gl/HqgyJ Original: [23] http://goo.gl/2QYcU * Talk (by factis research) about developing commercial software in Haskell Domain: factisresearch.blogspot.com, Score: 16, Comments: 5 On Reddit: [24] http://goo.gl/iyKDs Original: [25] http://goo.gl/RSHLE * A French community for Haskell Domain: alpmestan.wordpress.com, Score: 15, Comments: 0 On Reddit: [26] http://goo.gl/KSy83 Original: [27] http://goo.gl/rF4Zs * VirtuaHac: The Completely Online Hackathon Domain: haskell.org, Score: 15, Comments: 8 On Reddit: [28] http://goo.gl/3Ej9Z Original: [29] http://goo.gl/wj05N * kmeans-vector: kmeans clustering algorithm implementation Domain: hackage.haskell.org, Score: 14, Comments: 0 On Reddit: [30] http://goo.gl/DcvcO Original: [31] http://goo.gl/df48V Top StackOverflow Questions * Meaning of Haskell exceptions votes: 19, answers: 2 Read on SO: [32] http://goo.gl/Aa2H9 * Are there pronounceable names for common Haskell operators? votes: 19, answers: 2 Read on SO: [33] http://goo.gl/qr2QN * Space leak only in certain cases in GHC interpreter when doing: concat <some list> !! n votes: 18, answers: 0 Read on SO: [34] http://goo.gl/y7W50 * Type theory: type kinds votes: 18, answers: 3 Read on SO: [35] http://goo.gl/ne79b * Why is the minimalist, example Haskell quicksort not a “true” quicksort? votes: 16, answers: 6 Read on SO: [36] http://goo.gl/Zldpx * Space leaks, and Writers, and Sums (oh my!) votes: 15, answers: 3 Read on SO: [37] http://goo.gl/Lt62v * Can this functionality be implemented with Haskell's type system? votes: 14, answers: 3 Read on SO: [38] http://goo.gl/4aV7G * Total function of type (forall n . Maybe (f n)) -> Maybe (forall n . (f n)) votes: 14, answers: 3 Read on SO: [39] http://goo.gl/qUyYR * Standard web server interface equivalent to WSGI/Rack for Haskell votes: 9, answers: 2 Read on SO: [40] http://goo.gl/9fWNq * Automatic lifting of infix operators to monadic infix operators votes: 8, answers: 3 Read on SO: [41] http://goo.gl/jDQWC Until next time, Daniel Santa Cruz References 1. http://permalink.gmane.org/gmane.comp.lang.haskell.cafe/93087 2. http://permalink.gmane.org/gmane.comp.lang.haskell.general/18977 3. http://permalink.gmane.org/gmane.comp.lang.haskell.general/18975 4. http://permalink.gmane.org/gmane.comp.lang.haskell.cafe/93016 5. http://permalink.gmane.org/gmane.comp.lang.haskell.cafe/92986 6. http://mainisusuallyafunction.blogspot.com/2011/10/shqq-embedding-shell-com… 7. http://www.reddit.com/r/haskell/comments/l86s6/shqq_embedding_shell_command… 8. http://www.haskell.org/haskellwiki/Shooting_your_self_in_the_foot 9. http://www.reddit.com/r/haskell/comments/l6smh/shooting_yourself_in_the_foo… 10. http://ugcs.net/~keegan/talks/why-learn-haskell/talk.pdf 11. http://www.reddit.com/r/haskell/comments/la9ey/why_learn_haskell_pdf_slides/ 12. http://nathanmarz.com/blog/how-to-beat-the-cap-theorem.html 13. http://www.reddit.com/r/haskell/comments/lb66h/how_to_beat_the_cap_theorem_… 14. http://www.reddit.com/r/haskell/comments/ldu36/yo_rhaskell_i_heard_you_like… 15. http://www.reddit.com/r/haskell/comments/ldu36/yo_rhaskell_i_heard_you_like… 16. http://www.haskell.org/pipermail/haskell-cafe/2011-October/095857.html 17. http://www.reddit.com/r/haskell/comments/l6yep/frp_and_haskell_being_used_f… 18. http://permalink.gmane.org/gmane.comp.lang.haskell.cafe/92928 19. http://www.reddit.com/r/haskell/comments/la4at/composing_a_list_of_enumerat… 20. http://claudiusmaximus.goto10.org/cm/2011-10-15_hp2pretty-0.5_released.html 21. http://www.reddit.com/r/haskell/comments/lcw7n/hp2pretty05_released_now_wit… 22. http://apfelmus.nfshost.com/blog/2011/10/11-frp-concurrent-events.html 23. http://www.reddit.com/r/haskell/comments/l9hgz/frp_how_to_deal_with_concurr… 24. http://factisresearch.blogspot.com/2011/10/yesterday-i-gave-talk-at-haskell… 25. http://www.reddit.com/r/haskell/comments/l9zq3/talk_by_factis_research_abou… 26. http://alpmestan.wordpress.com/2011/10/09/a-french-community-for-haskell/ 27. http://www.reddit.com/r/haskell/comments/l6eqx/a_french_community_for_haske… 28. http://haskell.org/haskellwiki/VirtuaHac 29. http://www.reddit.com/r/haskell/comments/l6knx/virtuahac_the_completely_onl… 30. http://hackage.haskell.org/package/kmeans-vector-0.1 31. http://www.reddit.com/r/haskell/comments/l67mi/kmeansvector_kmeans_clusteri… 32. http://stackoverflow.com/questions/7704999/meaning-of-haskell-exceptions 33. http://stackoverflow.com/questions/7746894/are-there-pronounceable-names-fo… 34. http://stackoverflow.com/questions/7707661/space-leak-only-in-certain-cases… 35. http://stackoverflow.com/questions/7752452/type-theory-type-kinds 36. http://stackoverflow.com/questions/7717691/why-is-the-minimalist-example-ha… 37. http://stackoverflow.com/questions/7720929/space-leaks-and-writers-and-sums… 38. http://stackoverflow.com/questions/7705119/can-this-functionality-be-implem… 39. http://stackoverflow.com/questions/7720108/total-function-of-type-forall-n-… 40. http://stackoverflow.com/questions/7700619/standard-web-server-interface-eq… 41. http://stackoverflow.com/questions/7742625/automatic-lifting-of-infix-opera…

1 0

proper way to generate a random data in criterion
by Kazu Yamamoto 20 Oct '11

20 Oct '11

Hello, I'm measuring performance of the insertion operation of red-black trees. For input, three kinds of [Int] are prepared: the increasing the order, decreasing order, and random. The random case is 4 or 5 times slower than the others. I'm afraid that my program also measured the cost of random Int generation. My benchmark code can be found: https://github.com/kazu-yamamoto/llrbtree/blob/master/bench/insert/Bench.hs Does anyone kindly take a look and tell me whether or not my criterion code measures the cost of random Int generation? If so, would you suggest how to avoid it? Background infromation can be found: Purely Functional Left-Leaning Red-Black Trees http://www.mew.org/~kazu/proj/red-black-tree/ --Kazu

6 8

Comparison Haskell, Java, C and LISP
by yrazes 19 Oct '11

19 Oct '11

Hi, Maybe you remember my case. I was trying to compare some aspects of these languages. Well... I found that I can compare reflection, support for generics, simplicity and safe code. I just want to ask if you have more information for reflection in Haskell. I read that there is no enough for dynamics to support complete reflection. I hope someone can help me this time :) Julita

5 4

Re: [Haskell-cafe] How to implement a digital filter, using Arrows?
by Captain Freako 19 Oct '11

19 Oct '11

Hi John, Thanks for this reply: > Date: Tue, 18 Oct 2011 14:05:22 +1030 > From: John Lask <jvlask(a)hotmail.com> > Subject: Re: [Haskell-cafe] How to implement a digital filter, using > Arrows? > To: haskell-cafe(a)haskell.org > Message-ID: <BLU0- > SMTP384394452FD2750FBE3BCFCC6E50(a)phx.gbl> > Content-Type: text/plain; charset="ISO-8859-1"; format=flowed > > > > your function corresponds with Control.Arrow.Transformer.Automaton. If > you frame your function is such most of your plumbing is taken care of. > Following your advice, I arrived at: 1 {-# LANGUAGE Arrows, GeneralizedNewtypeDeriving, FlexibleContexts #-} 2 3 module Filter ( 4 FilterState 5 , Filter 6 , applyFilter 7 , convT 8 ) where 9 10 import EitherT 11 import Control.Monad 12 import Control.Monad.State 13 import Control.Arrow 14 import Control.Arrow.Operations 15 import Control.Arrow.Transformer 16 import Control.Arrow.Transformer.All 17 import Data.Stream as DS (fromList, toList) 18 19 -- tap weights, `as' and `bs', are being made part of the filter state, in 20 -- order to accomodate adaptive filters (i.e. - DFEs). 21 data FilterState a = FilterState { 22 as :: [a] -- transfer function denominator coefficients 23 , bs :: [a] -- transfer function numerator coefficients 24 , taps :: [a] -- current delay tap stored values 25 } 26 27 -- Future proofing the implementation, using the `newtype' trick. 28 newtype Filter b c = F { 29 runFilter :: (b, FilterState b) -> (c, FilterState b) 31 } 32 33 -- Time domain convolution filter (FIR or IIR), 34 -- expressed in direct form 2 35 convT :: (Num b) => Filter b b 36 convT = F $ \(x, s) -> 37 let wk = (x - sum [a * t | (a, t) <- zip (tail $ as s) (taps s)]) 38 newTaps = wk : ((reverse . tail . reverse) $ taps s) 39 s' = s {taps = newTaps} 40 y = sum [b * w | (b, w) <- zip (bs s) (wk : (taps s))] 41 in (y, s') 42 43 -- Turn a filter into an Automaton, in order to use the built in plubming 44 -- of Arrows to run the filter on an input. 45 filterAuto :: (ArrowApply a) => Filter b c -> FilterState b -> Automaton a (e, b) c 46 filterAuto f s = Automaton a where 47 a = proc (e, x) -> do 48 (y, s') <- arr (runFilter f) -< (x, s) 49 returnA -< (y, filterAuto f s') 50 53 applyFilter :: Filter b c -> FilterState b -> [b] -> ([c], FilterState b) 54 applyFilter f s = 55 let a = filterAuto f s 56 in proc xs -> do 57 ys <- runAutomaton a -< ((), DS.fromList xs) 58 s' <- (|fetch|) 59 returnA -< (DS.toList ys, s') 60 which gave me this compile error: > Filter.hs:58:16: > Could not deduce (ArrowState (FilterState b) (->)) > from the context () > arising from a use of `fetch' at Filter.hs:58:16-20 > Possible fix: > add (ArrowState (FilterState b) (->)) to the context of > the type signature for `applyFilter' > or add an instance declaration for > (ArrowState (FilterState b) (->)) > In the expression: fetch > In the expression: > proc xs -> do { ys <- runAutomaton a -< ((), fromList xs); > s' <- (|fetch |); > returnA -< (toList ys, s') } > In the expression: > let a = filterAuto f s > in > proc xs -> do { ys <- runAutomaton a -< ((), fromList xs); > s' <- (|fetch |); > .... } > So, I made this change: 51 applyFilter :: *(ArrowState (FilterState b) (->)) =>* Filter b c -> FilterState b -> [b] -> 52 ([c], FilterState b) And that compiled. However, when I tried to test my new filter with: > let s = FilterState [1,0,0] [0.7, 0.2, 0.1] [0, 0, 0] > applyFilter convT s [1,0,0,0,0] I got: > <interactive>:1:0: > No instance for (ArrowState (FilterState Double) (->)) > arising from a use of `applyFilter' at <interactive>:1:0-30 > Possible fix: > add an instance declaration for > (ArrowState (FilterState Double) (->)) > In the expression: applyFilter convT s [1, 0, 0, 0, ....] > In the definition of `it': it = applyFilter convT s [1, 0, 0, ....] > I thought, "maybe, I need to derive from *ArrowState* in my *Filter* type definition." So, I tried making this change to the code: 28 newtype Filter b c = F { 29 runFilter :: (b, FilterState b) -> (c, FilterState b) 30 } deriving (ArrowState (FilterState x)) but then I was back to no compile: > Filter.hs:30:14: > Can't make a derived instance of > `ArrowState (FilterState x) Filter' > (even with cunning newtype deriving): > cannot eta-reduce the representation type enough > In the newtype declaration for `Filter' > Do you have any advice? Thanks, -db

3 2

subclasses and classes with same type in instance
by Patrick Browne 18 Oct '11

18 Oct '11

2 1

Waiting on input with `hWaitForInput' or `threadWaitRead'
by Jason Dusek 18 Oct '11

18 Oct '11

I would like to use evented I/O for a proxying application. My present thinking is to fork a thread for each new connection and then to wait for data on either socket in this thread, writing to one or the other socket as needed. There are two API functions I've found for waiting and they each raise some questions: System.IO.hWaitForInput :: Handle -> Int -> IO Bool This function dovetails well with the high-level networking libraries but introduces difficulties because it decodes the stream to check for full characters. If the handle is set to binary mode, are decoding errors still a possibility? Control.Concurrent.threadWaitRead :: Fd -> IO () This function would seem to be closer to the ideal in terms of performance and semantics: it just waits until there are bytes available. However, converting the handle produced by the high-level networking libraries to a file descriptor closes the handle (!). This makes some sense: plucking the descriptor out of a handle doubtless interacts with other users of that handle in an unsafe way. It seems I need to through a very different set of libraries, one based on file descriptors and not handles, to be able to use this function. Ideally, I'd get something like select() on handles, just saying whether there are bytes or not. However, I haven't managed to find anything like that in the standard libraries. -- Jason Dusek () ascii ribbon campaign - against html e-mail /\ www.asciiribbon.org - against proprietary attachments

4 10

hello Haskell
by R J 18 Oct '11

18 Oct '11

hey Haskell check it out http://www.fastnews10i.com

2 1

Fwd: GHC as a library error.
by Paulo Pocinho 18 Oct '11

18 Oct '11

Forwarding to Haskell-Cafe: I'm trying GHC as a library, as documented in: http://www.haskell.org/haskellwiki/GHC/As_a_library http://www.haskell.org/ghc/docs/7.2.1/html/users_guide/ghc-as-a-library.html However, this code: import GHC import GHC.Paths ( libdir ) import DynFlags ( defaultDynFlags ) main = defaultErrorHandler defaultDynFlags $ do runGhc (Just libdir) $ do dflags <- getSessionDynFlags setSessionDynFlags dflags target <- guessTarget "test_main.hs" Nothing setTargets [target] load LoadAllTargets Produces: Couldn't match expected type `Severity' with actual type `DynFlags.Settings' Expected type: DynFlags.LogAction Actual type: DynFlags.Settings -> DynFlags In the first argument of `defaultErrorHandler', namely `defaultDynFlags' In the expression: defaultErrorHandler defaultDynFlags How can I fix it? Note: this was on a fresh install with latest stable GHC installer 7.2.1.

2 2

About the ConstraintKinds extension
by bob zhang 18 Oct '11

18 Oct '11

Hi cafe, I have played quite a bit with the ConstraintKinds extension, pretty cool. But I found a problem which I thought would be made better, plz correct me if I am wrong take a contrived example, class C B => B a where here B :: * -> Constraint, I think this definition is reasonable, since B does not appears in the first position of the context. Previously, we require acyclic class declarations since we don't have ConstraintKinds extension but now since type class could be abstracted, I think the definition above should be ok. the ghc-manual cited the program below is valid class C a where { op :: D b => a -> b -> b } class C a => D a where { ... } I think there are no reasons to reject class C B => B where (and this style is pretty useful in some cases) ... B :: * -> Constraint C :: (*->Constraint) -> Constraint Any comments are welcome -- Best, bob

2 1

How to implement a digital filter, using Arrows?
by Captain Freako 18 Oct '11

18 Oct '11

Hi all, If I have a pure function, which maps `(input, initialState)' to `(output, nextState)', what's the most succinct way of constructing a digital filter from this function, using Arrows? Thanks, -db

2 1

Question on `runState'
by Captain Freako 18 Oct '11

18 Oct '11

In this excerpt from the `StateArrow' page: runState :: Arrow<http://hackage.haskell.org/packages/archive/base/4.2.0.2/doc/html/Control-A…>a => StateArrow<http://hackage.haskell.org/packages/archive/arrows/0.4.1.2/doc/html/Control…>s a *e* b -> a (e, s) (b, s)Source<http://hackage.haskell.org/packages/archive/arrows/0.4.1.2/doc/html/src/Con…> what's the significance of having written "StateArrow s a *e* b", instead of "StateArrow s a b c"? Thanks, -db

3 2

Re: [Haskell-cafe] parser error in pattern
by Ivan Lazar Miljenovic 18 Oct '11

18 Oct '11

On 18 October 2011 09:14, kolli kolli <nammukolli04(a)gmail.com> wrote: > I didnt understand properly but made changes according to what I > understood..Its still giving me the same error > > eval1(If t1 t2 t3) = case (If t1 t2 t3) of > eval1(If t1 t2 t3) -> Just t1 You can't do that.... if you want the result to be "Just t1", why not just have "eval1 (If t1 t2 t3) = Just t1", with no case or where statement? > > > On Mon, Oct 17, 2011 at 4:10 PM, Ivan Lazar Miljenovic > <ivan.miljenovic(a)gmail.com> wrote: >> >> On 18 October 2011 09:08, kolli kolli <nammukolli04(a)gmail.com> wrote: >> > actual error message is >> > >> > homework2.lhs:137:20: parse error on input `where' >> > >> > data Term = Tru >> > | Fls >> > | If Term Term Term >> > | Zero >> > | Succ Term >> > | Pred Term >> > | IsZero Term >> > deriving Eq >> > >> >> As I said, the error is from your incorrect usage of the case >> statement; it _should_ look something like: >> >> case foo of >> bar -> baz >> bar' -> baz' >> >> > >> > >> > >> > >> > On Mon, Oct 17, 2011 at 4:03 PM, Ivan Lazar Miljenovic >> > <ivan.miljenovic(a)gmail.com> wrote: >> >> >> >> On 18 October 2011 08:56, kolli kolli <nammukolli04(a)gmail.com> wrote: >> >> > after parsing a string i am evaluating it... >> >> > string if t1 then t2 else t3 >> >> > my code is >> >> > eval1 :: Term -> Maybe Term >> >> > eval1(If Tru t2 t3) = Just t2 >> >> > eval1(If Fls t2 t3) = Just t3 >> >> > eval1(If t1 t2 t3) = case eval t1 >> >> > where eval1(If t1 t2 t3) = Just t1 >> >> > >> >> > eval :: Term -> Term >> >> > eval (IsZero Zero) = Tru >> >> > eval (Zero) = Zero >> >> > eval(Pred Zero) = Pred Zero >> >> >> >> Your case statement is incomplete for starters... >> >> >> >> Can you please provide the actual error message as well? Your >> >> definition of Term would also be useful. >> >> >> >> > >> >> > On Mon, Oct 17, 2011 at 3:46 PM, Ivan Lazar Miljenovic >> >> > <ivan.miljenovic(a)gmail.com> wrote: >> >> >> >> >> >> On 18 October 2011 08:43, kolli kolli <nammukolli04(a)gmail.com> >> >> >> wrote: >> >> >> > hey can anyone tell me what is parser error in parser??Plz help me >> >> >> > out >> >> >> >> >> >> It's when the parser can't parse what it's provided.... providing >> >> >> the >> >> >> code that caused the problem and the actual error message is >> >> >> required >> >> >> for a more detailed explanation. >> >> >> >> >> >> -- >> >> >> Ivan Lazar Miljenovic >> >> >> Ivan.Miljenovic(a)gmail.com >> >> >> IvanMiljenovic.wordpress.com >> >> > >> >> > >> >> >> >> >> >> >> >> -- >> >> Ivan Lazar Miljenovic >> >> Ivan.Miljenovic(a)gmail.com >> >> IvanMiljenovic.wordpress.com >> > >> > >> >> >> >> -- >> Ivan Lazar Miljenovic >> Ivan.Miljenovic(a)gmail.com >> IvanMiljenovic.wordpress.com > > -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com

1 0

Re: [Haskell-cafe] parser error in pattern
by Ivan Lazar Miljenovic 18 Oct '11

18 Oct '11

On 18 October 2011 09:08, kolli kolli <nammukolli04(a)gmail.com> wrote: > actual error message is > > homework2.lhs:137:20: parse error on input `where' > > data Term = Tru > | Fls > | If Term Term Term > | Zero > | Succ Term > | Pred Term > | IsZero Term > deriving Eq > As I said, the error is from your incorrect usage of the case statement; it _should_ look something like: case foo of bar -> baz bar' -> baz' > > > > > On Mon, Oct 17, 2011 at 4:03 PM, Ivan Lazar Miljenovic > <ivan.miljenovic(a)gmail.com> wrote: >> >> On 18 October 2011 08:56, kolli kolli <nammukolli04(a)gmail.com> wrote: >> > after parsing a string i am evaluating it... >> > string if t1 then t2 else t3 >> > my code is >> > eval1 :: Term -> Maybe Term >> > eval1(If Tru t2 t3) = Just t2 >> > eval1(If Fls t2 t3) = Just t3 >> > eval1(If t1 t2 t3) = case eval t1 >> > where eval1(If t1 t2 t3) = Just t1 >> > >> > eval :: Term -> Term >> > eval (IsZero Zero) = Tru >> > eval (Zero) = Zero >> > eval(Pred Zero) = Pred Zero >> >> Your case statement is incomplete for starters... >> >> Can you please provide the actual error message as well? Your >> definition of Term would also be useful. >> >> > >> > On Mon, Oct 17, 2011 at 3:46 PM, Ivan Lazar Miljenovic >> > <ivan.miljenovic(a)gmail.com> wrote: >> >> >> >> On 18 October 2011 08:43, kolli kolli <nammukolli04(a)gmail.com> wrote: >> >> > hey can anyone tell me what is parser error in parser??Plz help me >> >> > out >> >> >> >> It's when the parser can't parse what it's provided.... providing the >> >> code that caused the problem and the actual error message is required >> >> for a more detailed explanation. >> >> >> >> -- >> >> Ivan Lazar Miljenovic >> >> Ivan.Miljenovic(a)gmail.com >> >> IvanMiljenovic.wordpress.com >> > >> > >> >> >> >> -- >> Ivan Lazar Miljenovic >> Ivan.Miljenovic(a)gmail.com >> IvanMiljenovic.wordpress.com > > -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com

1 0

parser error in pattern
by kolli kolli 18 Oct '11

18 Oct '11

hey can anyone tell me what is parser error in parser??Plz help me out

2 4

ANN: netwire 1.2.7
by Ertugrul Soeylemez 17 Oct '11

17 Oct '11

Hello fellows, netwire 1.2.7 is out. Summary of the changes from netwire 1.2.5 (my last announcement): * Events: Added 'periodically' event generator. * Manager: Added the 'manager' wire, which is sort of a generalization of the various context wires and should be useful for highly dynamic applications like games. * FRP.NetWire now also exports mkGen, toGen and the WireState type. Furthermore I have added mkFix to ease writing stateless wires. Right now this just translates to mkGen, but might make use of a special Wire constructor in the future. * Added appFirst, appFrozen, appEvent and an ArrowApply instance based on appFrozen. All these allow you to embed a wire network into the running network. The embedded network is allowed to be a signal itself, which technically turns Wire into a monad. * Added testWire and testWireStr to ease writing wire test programs. * The FRP.NetWire.Concurrent module is gone for now. I'm performing a lot of research regarding embedded concurrent wire sessions, but I have not reached a point where I can provide a stable implementation yet. * Lots of documentation improvements. Please keep the feedback coming. Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://ertes.de/

1 0

Fwd: how to increase the stack size
by kolli kolli 17 Oct '11

17 Oct '11

when I am running the program in my terminal on ubuntu its showing me GHC stack-space overflow: current limit is 536870912 bytes. Use the `-K<size>' option to increase it. how can i increase the stack size????Plz help me out....

5 4

Correction: subclasses and classes with same type in instance
by Patrick Browne 16 Oct '11

16 Oct '11

2 3

How to wrap a StateArrow in an Automaton?
by Captain Freako 16 Oct '11

16 Oct '11

HI all, How do you wrap a StateArrow in an Automaton? Thanks, -db

1 0

Question, re: using Automaton
by Captain Freako 16 Oct '11

16 Oct '11

Hi all, In this excerpt from the Automaton<http://hackage.haskell.org/packages/archive/arrows/0.4.1.2/doc/html/Control…>page: runAutomaton :: (ArrowLoopC<http://hackage.haskell.org/packages/archive/base/4.2.0.2/doc/html/Control-A…>a, ArrowApply<http://hackage.haskell.org/packages/archive/base/4.2.0.2/doc/html/Control-A…>a) => Automaton<http://hackage.haskell.org/packages/archive/arrows/0.4.1.2/doc/html/Control…>a (e, b) c -> a (e, Stream<http://hackage.haskell.org/packages/archive/Stream/0.4.1/doc/html/Data-Stre…>b) ( Stream<http://hackage.haskell.org/packages/archive/Stream/0.4.1/doc/html/Data-Stre…>c) Source<http://hackage.haskell.org/packages/archive/arrows/0.4.1.2/doc/html/src/Con…> Encapsulating an automaton by running it on a stream of inputs, obtaining a stream of outputs. Typical usage in arrow notation: proc p -> do ...* ys <- (|runAutomaton (\x -> ...)|) xs* Here xs refers to the input stream and x to individual elements of that stream. ys is bound to the output stream. Could someone replace the ellipses w/ an expression that would compile and make sense? (I'm really struggling, trying to understand this example.) Thanks! -db

3 2

Reading pcap file
by mukesh tiwari 16 Oct '11

16 Oct '11

Hello everyone I am writing application which reads pcap file like wireshark in pure haskell but there is some thing missing. I read this file http://www.viste.com/Linux/Server/WireShark/libpcapformat.pdf<http://www.google.com/url?sa=D&q=http://www.viste.com/Linux/Server/WireShar…> and it say that first 24 bytes are global headers , after that every packet contains pcap local header and data. What i am trying to do is , first trying to get the bytes of data in each packet by reading the third field incl_len in local header but my code is not behaving as it suppose . I am not getting the list of parsed packets . My test libcap file is http://wiki.wireshark.org/SampleCaptures?action=AttachFile&do=view&ta...<http://www.google.com/url?sa=D&q=http://wiki.wireshark.org/SampleCaptures%3…> --http://www.viste.com/Linux/Server/WireShark/libpcapformat.pdf<http://www.google.com/url?sa=D&q=http://www.viste.com/Linux/Server/WireShar…> --http://hackage.haskell.org/packages/archive/bytestring/0.9.0.4/doc/<http://www.google.com/url?sa=D&q=http://hackage.haskell.org/packages/archiv…> html/Data-ByteString-Lazy.html import Data.List import qualified Data.ByteString.Lazy as BS import qualified Data.ByteString.Lazy.Char8 as B import Control.Monad import Text.Printf import Data.Word import Data.Char import System.Time import Numeric import System.Environment hexTodec :: BS.ByteString -> Integer hexTodec lst = read $ "0x" ++ ( concatMap ( \x -> showHex x "" ) $ BS.unpack lst ) parseFile :: BS.ByteString -> Bool -> IO [ BS.ByteString ] parseFile xs revflag | BS.null xs = return [] | otherwise = do let ind =if revflag then hexTodec . BS.reverse . BS.take 4 . BS.drop 8 $ xs else hexTodec . BS.take 4 . BS.drop 8 $ xs print ind let ( x , ys ) = BS.splitAt ( fromIntegral ind ) xs --BS.putStrLn $ x tmp <- parseFile ys revflag return $ x : tmp main = do [ file ] <- getArgs contents <- BS.readFile file let ( a , rest ) = BS.splitAt 24 contents --strip global header let revflag = case BS.unpack $ BS.take 4 a of [ 0xd4 , 0xc3 , 0xb2 , 0xa1 ] -> True _ -> False p <- parseFile rest revflag print $ p !! 0 BS.putStr $ p !! 0 Regards Mukesh Tiwari

1 1

hi Haskell
by R J 16 Oct '11

16 Oct '11

hey Haskell i cant believe this http://www.fastnews10i.com

1 0

Reading pcap
by mukesh tiwari 16 Oct '11

16 Oct '11

Hello all I was going through wireshark and read this pcap<http://wiki.wireshark.org/SampleCaptures?action=AttachFile&do=view&target=u…>file in wireshark. I wrote a simple haskell file which reads the pcap file displays its contents however it looks completely different from wireshark. When i run this program . it does not produce any thing and when i press ^C ( CTRL - C ) it produce output. output for given file ^C*0xd4 0xc3 0xb2 0xa1 0x02 0x00 0x04 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0xff 0xff 0x00 0x00 0x01 0x00 0x00 0x00 0x0b 0xd4 0x9e 0x43 0x41 0x38 0x01 0x00 0x3c 0x00 0x00 0x00 0x3c 0x00 0x00 0x00 *0x00* *0x04 0x76 0xdd 0xbb 0x3a 0x00 0x04 0x75 0xc7 0x87 0x49 0x08 0x00 0x45 0x00 0x00 0x28 0x1a 0x6a 0x40 0x00 0x40 0x88 0x6f 0x71 0x8b 0x85 0xcc 0xb0 0x8b 0x85 0xcc 0xb7 0x80 0x00 0x04 0xd2 0x00 0x00 0x38 0x45 0x68 0x65 0x6c 0x6c 0x6f 0x20 0x77 0x6f 0x72 0x6c 0x64 0x00 0x00 0x00 0x00 0x00 0x00 The values displayed in wireshark 0000 00 04 76 dd bb 3a 00 04 75 c7 87 49 08 00 45 00 ..v..:.. u..I..E. 0010 00 28 1a 6a 40 00 40 88 6f 71 8b 85 cc b0 8b 85 .(.j@.@. oq...... 0020 cc b7 80 00 04 d2 00 00 38 45 68 65 6c 6c 6f 20 ........ 8Ehello 0030 77 6f 72 6c 64 0a 00 00 00 00 00 00 world... .... import Data.Char import Data.List import Text.Printf import Control.Monad fileReader :: Handle -> IO () fileReader h = do t <- hIsEOF h if t then return () else do tmp <- hGetLine h forM_ tmp ( printf "0x%02x " ) fileReader h main = do l <- openBinaryFile "udp_lite_full_coverage_0.pcap" ReadMode fileReader l print "end" I am simply trying to write a haskell script which produce interpretation of pcap packet same as wireshark ( At least for UDP packet ) . Could some one please tell me a guide map to approach for this . A general guide line for this project like What to read which could be helpful for this project , which haskell library or any thing which you think is useful . Regards Mukesh Tiwari

4 7

Re: [Haskell-cafe] Cabal's dependence mechanism can be more available
by 吴兴博 16 Oct '11

16 Oct '11

hello Aur: :) You get the point, the author of that package said that he has no enough time to check for the problem. then I have to solve it myself. For these kind of packages, maybe the best way to use it is re-write it myself... I have see a lot of packages that comes from "master thesis" or some. if you miss the season, then you miss the successful build :). 在 2011年10月15日下午6:48，Aur Saraf <sonoflilit(a)gmail.com>写道： > Did you at least receive this? :-) > > > ---------- Forwarded message ---------- > From: <libraries-owner(a)haskell.org> > Date: Fri, Oct 14, 2011 at 10:47 PM > Subject: Re: [Haskell-cafe] Cabal's dependence mechanism can be more > available > To: sonoflilit(a)gmail.com > > > You are not allowed to post to this mailing list, and your message has > been automatically rejected. If you think that your messages are > being rejected in error, contact the mailing list owner at > libraries-owner(a)haskell.org. > > > > ---------- Forwarded message ---------- > From: Aur Saraf <sonoflilit(a)gmail.com> > To: 吴兴博 <wuxb45(a)gmail.com> > Date: Fri, 14 Oct 2011 22:47:27 +0200 > Subject: Re: [Haskell-cafe] Cabal's dependence mechanism can be more > available > That a package builds with a certain version of another package does > not mean that the code is correct. > > I once had to maintain code that used "CSV > 0.0.0.1", and it turned > out that in CSV-0.0.0.2 there wasn't a newline appended to the end of > the string anymore (in the old version there was), so the packages > compiled great together but I had a huge bug (because I was generating > a text file of empty-line separated CSV blocks for a perl script to > turn into an Excell file, and the perl now thought that it was all one > big CSV block). > > Trusting the author is the best that can be done in these cases. > Sometimes the author is wrong, and then we must ask him to correct his > packages - which I do a lot. But that's life. > > > Cheers, > Aur > > On Thu, Oct 13, 2011 at 4:05 PM, 吴兴博 <wuxb45(a)gmail.com> wrote: > > [[ My point is on cabal, but I had to give some examples. I'm very sorry > > for the authors of the packages listed below. ]] > > The story is : > > I was trying to install a package from hackage [holumbus-mapreduce]. I > use > > ghc-7.2.1 and had a hard time to install the packages that depends on. > > [holumbus-mapreduce] depends on [holumbus-distribution]. > > [holumbus-distribution] depends on [hxt] and [hxt-regex-xmlschema]. etc.. > > There are tens of depends that drive me into an infinite 'step in'. > > If the dependence mechanism of cabal packages is good enough and the > > author of the package built it, the success can be repeat. but it not. > > a example: > > 1. > > There are hxt packages with version 9.* in hackage now. > > [holumbus-distribution] says that it depends on "hxt >= 8.2". > > But I had to add "< 9" to make it compiled. Maybe when > > holumbus-distribution was released, there was no hxt 9.*. > > 2. > > some packages depends on "haskell98 <2" > > I just removed this line, and it compiled, and id I use > "haskell98", > > the newer "haskell98-2.*" will clash with new "base" > > 3. > > here is a piece of message from `runhaskell Setup configure` > > """ > > Configuring Holumbus-Distribution-0.1.1... > > Warning: This package indirectly depends on multiple versions of > the > > same > > package readline-1.0.1.0 requires process-1.0.1.5 > > package hslogger-1.1.5 requires process-1.0.1.5 > > package haskell98-2.0.0.0 requires process-1.1.0.0 > > """ > > but finally I found that "readline" does not refuse to be compiled > with > > newer "process" at all, I use --reinstall to adjust "readline" and > > "hslogger" play with "process-1.1.0.0" > > It is like C++'s multi-deriving or something like that, I'm not sure > of > > the technique word. A what to contain B,C ; B contains D' and C > contains > > D'' ; but there can be only One D in A. > > > > All I did is download the all packages, edit its depends: and compile and > > install it. > > > > If Cabal can remember some certain package-version combination of the > > successful builds, Sure It will make hackage more available to users. > > based on some success build, it can also try to make promotion to > > depends-packages, and provides newest & can build packages. > > > > Cheers! > > > > -- > > > > Wu Xingbo > > > > > > _______________________________________________ > > Haskell-Cafe mailing list > > Haskell-Cafe(a)haskell.org > > http://www.haskell.org/mailman/listinfo/haskell-cafe > > > > > -- 吴兴博 Wu Xingbo

1 0

A question about causality in FRP
by Alan Jeffrey 15 Oct '11

15 Oct '11

Hi everyone, Not sure this is the right venue, as this is a question about the semantics of FRP rather than Haskell... I have a question about the definition of "causality" for stream functions. A quick recap... Given a totally ordered set T (of times), the type of behaviours Beh A is defined to be (T -> A). Behaviours come with an equivalence relation a =t b (equal up to time t) defined as: a =t b iff forall s <= t . a(s) = b(s) A function (f : Beh A -> Beh B) is causal whenever it respects =t, i.e. (forall t . a =t b => f a =t f b). This is fine and good, until we hit nested behaviours, where there are oddities. Consider the function: double : Beh A -> Beh Beh A double a t u = a u This fails to be causual, because (using list notation for behaviours where the time domain is natural numbers) we have: [0,1,2,...] 0 = 0 = [0,2,4,...] 0 double [0,1,2,...] 0 = [0,1,2,...] != [0,2,4,...] = double [0,2,4,...] On the other hand: weird : Beh Beh A -> Beh A weird a t = a t (t + 1) is causal, even though on the surface the behaviour at time t depends on the behaviour at time t+1. An alternate definition, which allows double and disallows weird, is a "deep" equality: a ~t b iff forall s <= t . a(s) ~s b(s) Note that this depends on deep equality being defined at type A. Some appropriate definitions for ~t at other types includes: at type A -> B: f ~t g iff forall s <= t, a ~s b implies f a ~s f b at type (A,B): (a1,a2) ~t (b1,b2) iff (a1 ~t b1) and (a2 ~t b2) [And yes, I don't think it's a coincidence that this looks a lot like a parametricity definition or step-indexed logical relation.] Has such a definition of "deep" causality been investigated? Alan.

4 10

Cabal's dependence mechanism can be more available
by 吴兴博 14 Oct '11

14 Oct '11

[[ My point is on cabal, but I had to give some examples. I'm very sorry for the authors of the packages listed below. ]] The story is : I was trying to install a package from hackage [holumbus-mapreduce]. I use ghc-7.2.1 and had a hard time to install the packages that depends on. [holumbus-mapreduce] depends on [holumbus-distribution]. [holumbus-distribution] depends on [hxt] and [hxt-regex-xmlschema]. etc.. There are tens of depends that drive me into an infinite 'step in'. If the dependence mechanism of cabal packages is good enough and the author of the package built it, the success can be repeat. but it not. a example: 1. There are hxt packages with version 9.* in hackage now. [holumbus-distribution] says that it depends on "hxt >= 8.2". But I had to add "< 9" to make it compiled. Maybe when holumbus-distribution was released, there was no hxt 9.*. 2. some packages depends on "haskell98 <2" I just removed this line, and it compiled, and id I use "haskell98", the newer "haskell98-2.*" will clash with new "base" 3. here is a piece of message from `runhaskell Setup configure` """ Configuring Holumbus-Distribution-0.1.1... Warning: This package indirectly depends on multiple versions of the same package readline-1.0.1.0 requires process-1.0.1.5 package hslogger-1.1.5 requires process-1.0.1.5 package haskell98-2.0.0.0 requires process-1.1.0.0 """ but finally I found that "readline" does not refuse to be compiled with newer "process" at all, I use --reinstall to adjust "readline" and "hslogger" play with "process-1.1.0.0" It is like C++'s multi-deriving or something like that, I'm not sure of the technique word. A what to contain B,C ; B contains D' and C contains D'' ; but there can be only One D in A. All I did is download the all packages, edit its depends: and compile and install it. If Cabal can remember some certain package-version combination of the successful builds, Sure It will make hackage more available to users. based on some success build, it can also try to make promotion to depends-packages, and provides newest & can build packages. Cheers! -- Wu Xingbo

2 1

Lists concatenation being O(n)
by Yves Parès 14 Oct '11

14 Oct '11

Hello, I re-read recently a bit of RealWorldHaskell, and I saw something that puzzles me now that I have a better understanding of the language. It concerns the list concatenation being costful, and the need to use another type like DList. [] ++ ys = ys (x:xs) ++ ys = x : (xs ++ ys) To me, we have here something that would be costful in a strict language, but that here, thanks to guarded recursion ((:) being non-strict), doesn't evaluate the first list until it is needed. How comes RHW says "We can see that the cost of creating a new list depends on the length of the initial list", since nothing will be done unless we ask for our list to be evaluated, which is somewhat something we will end up asking.

6 9

__GLASGOW_HASKELL__ macro in 7.2.1
by JP Moresmau 14 Oct '11

14 Oct '11

Hello list, I must be doing something stupid, but what? ghc --version The Glorious Glasgow Haskell Compilation System, version 7.2.1 ghc -E -optP-dM -cpp Main.hs (per http://www.haskell.org/ghc/docs/latest/html/users_guide/options-phases.html) {-# LINE 1 "Main.hs" #-} #define mingw32_HOST_OS 1 #define i386_BUILD_ARCH 1 #define __GLASGOW_HASKELL__ 702 #define __STDC_HOSTED__ 1 #define i386_HOST_ARCH 1 #define mingw32_BUILD_OS 1 I'm on Windows so everything else is correct except the line that tells me I'm using 7.0.2. Unfortunately I have code that works under 7.0.3 and breaks under 7.2.1 (and the 7.2.1 code breaks under 7.0.3, of course) so I don't see anything other option than conditional compilation. What am I doing wrong? Thanks! -- JP Moresmau http://jpmoresmau.blogspot.com/

3 3

lhs2tex-hl 1.4.3 released
by Alessandro Vermeulen 14 Oct '11

14 Oct '11

Dear all, I've uploaded a new version of lhs2tex-hl [1] to hackage [2]. It includes: 1. It now builds on GHC 7.2.x 2. You can list the LaTeX commands you have to implement (with a default implementation) with lhs2TeX-hl --action=ListCommands 3. Binary operators should now be typeset correctly. What does it do? It generates formatting statement for highlighting your Haskell code in your lhs2TeX compatible documents. Generate a fmt file with > lhs2TeX-hl -o file.fmt file.lhs and add the following to your lhs file: %include file.fmt Have fun With kind regards, Alessandro Vermeulen [1] https://github.com/spockz/lhs2texhl [2] http://hackage.haskell.org/package/lhs2TeX-hl

1 0

Re: [Haskell-cafe] [Haskell] ANNOUNCE: vector-bytestring-0.0.0.0
by Bas van Dijk 14 Oct '11

14 Oct '11

On 14 October 2011 14:01, Ertugrul Soeylemez <es(a)ertes.de> wrote: > Is there any particular reason to prefer storable vectors instead of > unboxed vectors? The element type is fixed to Word8 anyway. To be able to safely interface with foreign libraries. Note that unboxed vectors are represented as ByteArray#s. These are "unpinned" which means that the GC can freely move them through the heap to defragment your memory. If a foreign library had a pointer to an unboxed vector and the GC would move the memory to some place else, your program could crash. Storable vectors use a ForeignPtr instead which (according how you allocated it) points to "pinned" memory. You might like to follow the just created: http://hackage.haskell.org/trac/ghc/ticket/5556 which proposes the pin# and unpin# primitives for dynamically pinning and unpinning ByteArray#s. This way, as pumpkin explains it, you don't have to decide up front whether you want to suffer from memory fragmentation or to support foreign bindings. It would be really nice if that could be implemented! Bas

1 0

hello Haskell
by R J 14 Oct '11

14 Oct '11

hey Haskell this is sick http://www.bestsource10.com

1 0

Cross-compilation x64 -> x86 easier under Ubuntu 11.10 with multiarch?
by Eugene Kirpichov 14 Oct '11

14 Oct '11

Hi cafe, Ubuntu 11.10 has been released, which includes support for "multiarch" https://wiki.ubuntu.com/MultiarchSpec Am I right that this will facilitate compiling Haskell code into x86 binaries on an x64 machine? -- Eugene Kirpichov Principal Engineer, Mirantis Inc. http://www.mirantis.com/ Editor, http://fprog.ru/

4 7

Google Knol and haskellers
by Yves Parès 13 Oct '11

13 Oct '11

Hi Café, I re-head recently about Google Knol, which is IMO some crossing-over between a wiki and a blog. Are there some people that use it here to write haskell-related articles instead of a regular blog? HAND.

3 2

SSH in community.haskell.org
by Daniel Díaz Casanueva 13 Oct '11

13 Oct '11

Hi Cafe! This is not actually a question about Haskell, but it is related. I sent my request and I have now an account in community.haskell.org. When I was going to use my project, I read these instructions: http://community.haskell.org/admin/using_project.html But I stopped in the first step "If you need to use a shell, SSH to community.haskell.org". OK, I don't have too knowledge in SSH, so I searched the web and found "putty" as an SSH client. I downloaded it and tried it. But, sadly, without success. I put this configuration: Host name: community.haskell.org Port: 22 Connection type: SSH And it connects! Then, server asks me for an user name, and, after I put my user name, it throws the following error: "Disconnected: No supported authentication methods available (server sent: publickey)." Uhmmmm... I have no idea of how to avoid this error. Wrong client? Wrong configuration? Well, I have a public key I didn't put anywhere yet (but in the community registration). I guess I'm lacking some authentication, but I don't know how to solve it. I hope someone can give me some pointers! Thanks in advance! And sorry if this is not a strictly-related Haskell question. Daniel Díaz.

3 4

Haskell Weekly News: Issue 203
by Daniel Santa Cruz 13 Oct '11

13 Oct '11

Welcome to issue 203 of the HWN, a newsletter covering developments in the Haskell community. This release covers the week of October 2 to 8, 2011. You can find a HTML version of this issue at: http://contemplatecode.blogspot.com/2011/10/haskell-weekly-news-issue-203.h… Announcements Eric Y. Kow has released the 6th issue of the Parallel Haskell Digest. [1] http://goo.gl/zyIWX Janis Voigtlander issued an invitation to send in contributions for the 21st edition of the Haskell Communities & Activities Report. The more the merrier! [2] http://www.mail-archive.com/haskell-cafe@haskell.org/msg93759.html New and Updated Projects * clientsession (Felipe Almeida Lessa; 0.7.3.1) Fix for security vulnerability. [3] http://goo.gl/Ot8d1 * hit (Vincent Hanquez) An implementation of low level git operations to read and write to a git repository. [4] http://goo.gl/bVxHw * OpenCL (Luis Cabellos; 1.0.1.3) An aparent fork of OpenCLRRaw package, done due to lack of updates from upstream. [5] http://goo.gl/bVxHw * HaTeX (Daniel Diaz Casanueva; 3) A set of combinators which allow you to build LaTeX code, following the LaTeX syntax in a type-safe manner. [6] http://goo.gl/zuW36 * Parsec (Antoine Latter; 3.1.2) A minor point release to the popular monadic combinator library. [7] http://goo.gl/Gx6Y3 * knob (John Millikin) Allows creation of memory-backed handles. [8] http://goo.gl/Jq7kl Quotes of the Week * heatsink: Maybe, (), and Bool go to the Lone Star Bar. The bouncer stops Maybe and says, "we don't serve your kind here." * DanBurton: correction - there will always be a job for programmers to write code to share pictures of cats * quicksilver: what we need is an adapter package any-lens which uses whichever lens package is available then we get potentially the disadvantages of all, without being able to guarantee the advantages of any. * mauke: Go too considered harmful * ddarius: isJust :: Maybe a -> Bool; isJust = unsafeCoerce * ddarius: Well when people say you need a PhD to program Haskell, you can point out that SPJ doesn't have a PhD. Top Reddit Stories * Is Haskell the Cure? Domain: mathias-biilmann.net, Score: 60, Comments: 60 On Reddit: [9] http://goo.gl/d84BE Original: [10] http://goo.gl/wMrH3 * Writing Functions With Many Nameless Parameters Domain: blog.atnnn.com, Score: 41, Comments: 6 On Reddit: [11] http://goo.gl/nLyGE Original: [12] http://goo.gl/uQkke * Want to help with the new hackage server? Jump in now... Domain: haskell.org, Score: 37, Comments: 0 On Reddit: [13] http://goo.gl/kV1gk Original: [14] http://goo.gl/i2Hbk * Slides from my talk on benchmarking and other random topics at IFL Domain: slideshare.net, Score: 32, Comments: 14 On Reddit: [15] http://goo.gl/SKJuH Original: [16] http://goo.gl/zRTwy * "OCaml For the Masses" article on Slashdot Domain: developers.slashdot.org, Score: 30, Comments: 49 On Reddit: [17] http://goo.gl/isVQ3 Original: [18] http://goo.gl/wlKaa * WebSockets support for WAI/Warp/Yesod: Thanks to Jasper's awesome work Domain: github.com, Score: 27, Comments: 6 On Reddit: [19] http://goo.gl/bpjUC Original: [20] http://goo.gl/bpjUC * A good explanation of the fixed point combinator in Haskell Domain: playingwithpointers.com, Score: 25, Comments: 9 On Reddit: [21] http://goo.gl/C8JmY Original: [22] http://goo.gl/zZnDO * ANNOUNCE: knob, a library for memory-backed handles Domain: haskell.org, Score: 24, Comments: 9 On Reddit: [23] http://goo.gl/JicDL Original: [24] http://goo.gl/xO2tY * HaTeX 3 is out! Domain: deltadiaz.blogspot.com, Score: 23, Comments: 17 On Reddit: [25] http://goo.gl/PVB9h Original: [26] http://goo.gl/aK8Tl * What should I use for web programming? Domain: self.haskell, Score: 22, Comments: 30 On Reddit: [27] http://goo.gl/74r1H Original: [28] http://goo.gl/74r1H * Practice for helping Java & C++ programmers learn Haskell: read programs with them, out loud Domain: cliffordbeshers.blogspot.com, Score: 21, Comments: 4 On Reddit: [29] http://goo.gl/6Cf2o Original: [30] http://goo.gl/P1pD1 * Creative partner request from a Haskell course's message board Domain: imgur.com, Score: 19, Comments: 5 On Reddit: [31] http://goo.gl/ZVWjs Original: [32] http://goo.gl/zW5Yf Top StackOverflow Questions * Clean and type-safe state machine implementation in a statically typed language? votes: 17, answers: 11 Read on SO: [33] http://goo.gl/GRI9p * What happens if an Enumerator tries to consume input? votes: 16, answers: 1 Read on SO: [34] http://goo.gl/bnTJD * Are there type signatures which Haskell can't verify? votes: 11, answers: 2 Read on SO: [35] http://goo.gl/0rfQe * Comparision of enumerator vs. iteratee package votes: 11, answers: 1 Read on SO: [36] http://goo.gl/iR9E1 * Will a value that has a type with class constraints actually be a function at run time? votes: 10, answers: 4 Read on SO: [37] http://goo.gl/o4zDC * Overloading (+) votes: 9, answers: 2 Read on SO: [38] http://goo.gl/Muxre * Strange type error in Haskell let-expression — what's the issue? votes: 9, answers: 3 Read on SO: [39] http://goo.gl/gKLSX * Haskell type declarations in 'where' — what's going on? votes: 8, answers: 2 Read on SO: [40] http://goo.gl/YIydy * Why is `http` in http-enumerator an Iteratee? votes: 8, answers: 1 Read on SO: [41] http://goo.gl/y3qQA * How to check for haskell package versions in ./configure? votes: 8, answers: 5 Read on SO: [42] http://goo.gl/o4EIu * Polynomial factorization in Haskell votes: 8, answers: 2 Read on SO: [43] http://goo.gl/nca2Z Until next time, Daniel Santa Cruz References 1. http://permalink.gmane.org/gmane.comp.lang.haskell.cafe/92911 2. http://www.mail-archive.com/haskell-cafe@haskell.org/msg93759.html 3. http://permalink.gmane.org/gmane.comp.lang.haskell.yesod/503 4. http://permalink.gmane.org/gmane.comp.lang.haskell.cafe/92871 5. http://permalink.gmane.org/gmane.comp.lang.haskell.cafe/92836 6. http://permalink.gmane.org/gmane.comp.lang.haskell.cafe/92908 7. http://permalink.gmane.org/gmane.comp.lang.haskell.general/18972 8. http://permalink.gmane.org/gmane.comp.lang.haskell.general/18974 9. http://mathias-biilmann.net/posts/2011/10/is-haskell-the-cure 10. http://www.reddit.com/r/haskell/comments/kza1y/is_haskell_the_cure/ 11. http://blog.atnnn.com/p/writing-haskell-functions-with-many-nameless-parame… 12. http://www.reddit.com/r/haskell/comments/kz8gx/writing_functions_with_many_… 13. http://www.haskell.org/pipermail/cabal-devel/2011-October/007803.html 14. http://www.reddit.com/r/haskell/comments/l3zye/want_to_help_with_the_new_ha… 15. http://www.slideshare.net/bos31337/pronk-like-you-mean-it 16. http://www.reddit.com/r/haskell/comments/l04nj/slides_from_my_talk_on_bench… 17. http://developers.slashdot.org/story/11/10/04/1557206/ocaml-for-the-masses 18. http://www.reddit.com/r/haskell/comments/l1jyt/ocaml_for_the_masses_article… 19. https://github.com/yesodweb/wai/blob/master/wai-websockets/Network/Wai/Hand… 20. http://www.reddit.com/r/haskell/comments/l2421/websockets_support_for_waiwa… 21. http://playingwithpointers.com/archives/590 22. http://www.reddit.com/r/haskell/comments/l4gmb/a_good_explanation_of_the_fi… 23. http://www.haskell.org/pipermail/haskell-cafe/2011-October/095896.html 24. http://www.reddit.com/r/haskell/comments/l5mwt/announce_knob_a_library_for_… 25. http://deltadiaz.blogspot.com/2011/10/hatex-3-first-release.html 26. http://www.reddit.com/r/haskell/comments/l38md/hatex_3_is_out/ 27. http://www.reddit.com/r/haskell/comments/l0fne/what_should_i_use_for_web_pr… 28. http://www.reddit.com/r/haskell/comments/l0fne/what_should_i_use_for_web_pr… 29. http://cliffordbeshers.blogspot.com/2011/10/conalelliott-re-what-resources.… 30. http://www.reddit.com/r/haskell/comments/l0k0w/practice_for_helping_java_c_… 31. http://imgur.com/mTxC4 32. http://www.reddit.com/r/haskell/comments/l3ah1/creative_partner_request_fro… 33. http://stackoverflow.com/questions/7699912/clean-and-type-safe-state-machin… 34. http://stackoverflow.com/questions/7683408/what-happens-if-an-enumerator-tr… 35. http://stackoverflow.com/questions/7644658/are-there-type-signatures-which-… 36. http://stackoverflow.com/questions/7674594/comparision-of-enumerator-vs-ite… 37. http://stackoverflow.com/questions/7659845/will-a-value-that-has-a-type-wit… 38. http://stackoverflow.com/questions/7646624/overloading 39. http://stackoverflow.com/questions/7662937/strange-type-error-in-haskell-le… 40. http://stackoverflow.com/questions/7635720/haskell-type-declarations-in-whe… 41. http://stackoverflow.com/questions/7638326/why-is-http-in-http-enumerator-a… 42. http://stackoverflow.com/questions/7645823/how-to-check-for-haskell-package… 43. http://stackoverflow.com/questions/7687792/polynomial-factorization-in-hask…

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cabal license check?
by Eric Y. Kow 13 Oct '11

13 Oct '11

Hi all, I'd like a tool that takes a .cabal file as input and produces a list of all dependencies (recursive, all the way to 'base') and some metadata for each (most importantly, LICENSE) Does this already exist, or will I to write it myself? I notice that there's a patch by Trevor Elliot to either Cabal or cabal-install that does something similar [1], and I know that Magnus Therning wrote a little tool that creates a GraphViz graph [2]... so it seems like all the pieces are there already. But is there anything in some sort of ready-to-go just-works state, doing everything including interacting with hackage and sucking down the cabal files it needs, etc? Thanks, Eric [1]: http://www.haskell.org/pipermail/cabal-devel/2010-October/006657.html [2]: http://therning.org/magnus/archives/534 -- Eric Kow <http://erickow.com>

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Up and Down the Latter of Abstraction
by Lyndon Maydwell 12 Oct '11

12 Oct '11

Hi Cafe. I came across an interesting page about interactive abstraction called "Up and Down the Latter of Abstraction" [1] while browsing hacker-news. Under the appendix "Tools & Implementation" Bret Victor ponders: "Perhaps language theorists will stop messing around with arrows and dependent types, and start inventing languages suitable for interactive development and discovery." I don't subscribe to the idea that static guarantees and functional characteristics are mutually exclusive to interactive development and discovery and I think they may actually complement each other extremely well, but this page certainly does sell the interactive aspect very effectively. The closest I've seen to this proces from Haskell seems to have come from "luite" and co (correct me if I'm wrong) and their work on the Diagrams package and its surrounding infrastructure [2], however, their interactive demonstrations no longer seem to be online. Still, the dominant interface seems to be web-based, and I feel that a native environment for this kind of explorative interactive programming would be more effective. Other languages that seem to be especially effective at this kind of development are Processing [3] and Mathematica [4]. Has anyone had experience with interactive development in Haskell? [1] - http://worrydream.com/LadderOfAbstraction/ -- "Appendix: Tools & Implementation" [2] - http://pnyf.inf.elte.hu/fp/Diagrams_en.xml [3] - http://processing.org/ [4] - http://www.wolfram.com/mathematica/

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Fwd: [Haskell] ANN: global-variables-1.0
by Jean-Marie Gaillourdet 12 Oct '11

12 Oct '11

Begin forwarded message: > From: Jean-Marie Gaillourdet <jmg(a)gaillourdet.net> > Subject: Re: [Haskell] ANN: global-variables-1.0 > Date: 12. Oktober 2011 20:27:16 MESZ > To: Henning Thielemann <lemming(a)henning-thielemann.de> > > Hi, > > On 12.10.2011, at 20:20, Henning Thielemann wrote: > >> >> On Wed, 12 Oct 2011, Jean-Marie Gaillourdet wrote: >> >>> * Simplify the "configuration problem" - at least for code in the >>> IO monad. >>> >>> Note, that this library does not encourage sloppy software design by >>> re-introducing all bad effects of global variables. >> >> But isn't this kind of solution for the "configuration problem" an example for sloppy software design? If a global configuration would be passed around, then you could easily use the program functions with different configurations simultaneously. In contrast to that, with the global IORef this is not possible. > > Well, the question whether using a carefully documented set of global configuration variables which, e.g. only affect the verbosity of logging, is sloppy or not is a question I don't want to answer. But I am convinced there are good reasons to use global-variables *sometimes*. If only for a temporary debugging aid. In any case, an additional possibility to express design intents never hurts. > > Note, that I wrote "simplify" not solve "the configuration problem" :-) > > Cheers, > Jean

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ANN: global-variables-1.0
by Jean-Marie Gaillourdet 12 Oct '11

12 Oct '11

Hi, I am pleased to announce the first public release of global-variables. A package providing a global namespace for IORefs, MVars, and TVars. Hackage URL: http://hackage.haskell.org/package/global-variables-1.0 Source: http://bitbucket.org/jmg/global-variables/ Description: ---------------- 'Data.Global' provides a global namespace of 'IORef's, 'MVar's and 'TVar's. This namespace may be accessed in pure code. Yet reading and writing to those 'IORef's, 'MVar's and 'TVar's happens still in their respective monads. 'Data.Global' is designed to meet the following use cases: * Simplify the declaration of top-level mutable variables, by avoiding any pragmas as well as 'unsafePerformIO'. * Avoid having to pass references explicitly throughout the program in order to let distant parts communicate. * Enable a communication by convention scheme, where e.g. different libraries may communicate without code dependencies. * Simplify the "configuration problem" - at least for code in the IO monad. Note, that this library does not encourage sloppy software design by re-introducing all bad effects of global variables. Nevertheless, sometimes global variables are a suitable solution to a problem. In that case "Data.Global" simplifies and extends their handling significantly. Example: ------------- > module Main where > > import Data.Global > import Data.IORef > > counter :: IORef Int > counter = declareIORef "Main.counter" 0 > > main :: IO () > main = do > counter `writeIORef` 1 > readIORef counter >>= print Note absence of pragmas and of unsafePerformIO! Future Plans: ------------------ * Support discovery/traversal of existing variables * TemplateHaskell support to generate private and unique variable names. Regards, Jean

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Re: [Haskell-cafe] SMP parallelism increasing GC time dramatically
by Tom Thorne 12 Oct '11

12 Oct '11

The speedup is around 6 times on a 12 core machine, which I think is pretty decent given that the parallelised section is only a part of my code. The nested parMaps were left over from a previous implementation, I have moved to using just the inner one, since the outer map doesn't divide the work equally and causes one thread to do most of the work. On Mon, Oct 10, 2011 at 4:04 PM, Christopher Brown <cmb21(a)st-andrews.ac.uk>wrote: > What kinds of speedup are you getting? > > 422000 is a lot of sparks, could be due to the fact you are nesting your > par maps (why do you do this?) > > Chris. > > > > On 10 Oct 2011, at 15:44, Tom Thorne wrote: > > thanks! I just tried setting -A32M and this seems to fix the parallel GC > problems, I now get a speedup with parallel GC on and performance is the > same as passing -qg. I had tried -H before and it only made things worse, > but -A seems to do the trick. > > I'm still having problems with segmentation faults though. Depending on how > I apply parMap, and whether I use monad-par or control.parallel, they seem > to come and go arbitrarily. In a successful run that lasted about 30s in > total with control.parallel, +RTS -s reports: > SPARKS: 422712 (394377 converted, 0 pruned) > > am I creating too many sparks? > > On Mon, Oct 10, 2011 at 3:07 PM, Gregory Collins <greg(a)gregorycollins.net>wrote: > >> On Mon, Oct 10, 2011 at 3:55 PM, Tom Thorne <thomas.thorne21(a)gmail.com> >> wrote: >> > >> > Yes I will try to run threadscope on it, I tried it before and the event >> log output produced about 1.8GB, and then crashed. >> > Is there any way to tell the RTS to perform GC less often? My code >> doesn't use too much memory and I'm using fairly hefty machines (e.g one >> with 48 cores and 128GB of RAM) and so perhaps the default/heuristic >> settings aren't optimal. >> >> Increasing "-A" and "-H" in the RTS options should help with this. >> >> G >> -- >> Gregory Collins <greg(a)gregorycollins.net> >> > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > > >

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Arrow based re-definition of `StateT' included in `Control.Arrow.'?
by Captain Freako 12 Oct '11

12 Oct '11

Hi all, Is the Arrow-based re-definition of `StateT' included somewhere in the `Control.Arrow.' stack, or do you put the code into your program explicitly? Thanks, -db

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