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Experiments in Haskell Packaging
by Chris Dornan 02 Jan '12

02 Jan '12

Hi All, The http://justhub.org Haskell distribution for Enterprize Linux (RHEL/CentOS 5 & 6) is now live. The distribution deviates from current practice. When you upgrade to a new Platform from justhub.org you add the new platform to your Haskell infrastructure rather than replacing the old platform with a new one. Why? **Stability**: Enterprise Linux places a strong emphasis on stability and updating packages should not break things. (This has provided some challenges for us as RHEL 5 is still using GCC 4.1.2 and Binutils 2.17.50.) **Flexibility**: Different projects will in general need to work with different versions of the platform and toolkits and upgrade according to their own schedules. I believe Haskell’s strong-typing sharpens the need for this. Production projects will need to upgrade according to their own schedules while other projects will want to stay up-to-date. In general when you check out a source tree you want to build with the tools and libraries that it has been tested with and move on according to the project’s timetable. **Sandboxes**: The same mechanism for managing the multiple toolkits and platforms can be adapted to provide an integrated sandbox utility. The logic that dictates that projects have different tool-chain requirements applies to the user packages too. (‘Handbox’ doesn’t really work so we use **Hubs** instead.) **Package Deletion**: The infrastructure can also be expanded to complete the package management tools with package removal and garbage collection of library code. **The Catalogue**: All of the GHC releases can be added as they become available. In general the distribution works just like any other – after an upgrade invoking ‘ghc’ without any other configuration will invoke the compiler for that latest platform, which should behave as it would on any other (working) distribution. But after an upgrade: o any projects configured to work with specific tool chains and libraries will continue undisturbed; o you can create a new hub based on the new platform and experiment with it on newly-checked-out source tree without disturbing an existing working tree (or just swap the hub into an existing work tree and back out again if things don’t work out); o even on release of a new version of a package (or if you want to experiment with your existing packages) you can easily duplicate an existing hub and delete, upgrade and add packages on a topic branch. Of course ‘serious developers’ have been doing this with home-brew infrastructure for ever. Nevertheless I have found doing it with well-integrated tools to be quite liberating. It might also help new users to make the transition to serious developers more quickly. Thoughts anyone? Chris

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Grok Monad Transformers - some help needed
by Steve Horne 02 Jan '12

02 Jan '12

I'm having another go at figuring out Monad Transformers, starting at the same point I've started and stopped the last couple of times. That's this tutorial... http://blog.sigfpe.com/2006/05/grok-haskell-monad-transformers.html Onion layers, lift etc - I get that. But I've never actually got anything to work - and therefore never built the confidence to move on. Problem 1 - this is literate Haskell. I've tried feeding it to haddock - all I get is an error about it lacking a main. I don't know what to actually do with this after putting it in a *.lhs file. No big deal, but... Problem 2 - even cutting the code out, shoving it in a *.hs file, and :loading it into GHCi, I still get a lot of errors. For the functions test1 and test2, the fixes were explicit type signatures. Easy enough to figure out... test1 :: State Int (Int, Int) test2 :: State String (String, String) I guess the basic issue is the same with test3 (and though I haven't tried the others today, probably test5 and test7 too). The trouble there is that I don't know what those type signatures should be because I don't know that much about monad transformers and how they can work. I can see what's going on in the body of test3, but that is a very small amount of understanding - the type signatures are important. And I can't use :type because GHCi is rejecting the code. In short... HELP!!!

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Dutch FP day 2012, January 6; ; reminder, and happy new year to all of you
by S D Swierstra 02 Jan '12

02 Jan '12

We are happy to announce that the next Dutch functional programming day will take place on January 6, 2012, at the university campus "de Uithof" of Utrecht University. The program, participants registered thus far, and further details can be found at: http://www.cs.uu.nl/wiki/bin/view/FPDag2012/WebHome If you are aware of people who might not be on the mailing list and might be interested (e.g. your students), please point this information out to them. Please do not forget to tell me that you whether you want to go to the dinner too. Best, hoping to see you all, Doaitse

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Composing Enumeratees in enumerator
by Michael Craig 02 Jan '12

02 Jan '12

I've been looking for a way to compose enumeratees in the enumerator package, but I've come up with nothing so far. I want this function (=$=) :: Monad m => Enumeratee a0 a1 m b -> Enumeratee a1 a2 m b -> Enumeratee a0 a2 m b I'm building a modular library on top of enumerator that facilitates reading time series data from a DB, applying any number of transformations to it, and then writing it back / doing something else with it. I'd like to be able to write simple transformations (enumeratees) and compose them without binding them to either a db reader (enumerator) or db writer (iteratee). I've been looking at the iterIO package as a possible alternative, because it seems to allow easy composition of Inums (enumeratees). I'm a little skittish of it because it seems unpopular next to enumerator. Thoughts on these issues? Cheers, Mike S Craig

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Installing glib
by Victor Miller 02 Jan '12

02 Jan '12

I have the Haskell Platform (version 7.0.4 of ghc) installed on my macbook (OS X 10.7 Lion) and I'd like to install glib. However, when I try cabal install glib, I get: cabal install glib Resolving dependencies... [1 of 2] Compiling SetupWrapper ( /tmp/glib-0.12.25777/glib-0.12.2/SetupWrapper.hs, /tmp/glib-0.12.25777/glib-0.12.2/dist/setup/SetupWrapper.o ) [2 of 2] Compiling Main ( /tmp/glib-0.12.25777/glib-0.12.2/Setup.hs, /tmp/glib-0.12.25777/glib-0.12.2/dist/setup/Main.o ) Linking /tmp/glib-0.12.25777/glib-0.12.2/dist/setup/setup ... ld: warning: could not create compact unwind for _ffi_call_unix64: does not use RBP or RSP based frame [1 of 2] Compiling Gtk2HsSetup ( Gtk2HsSetup.hs, dist/setup-wrapper/Gtk2HsSetup.o ) [2 of 2] Compiling Main ( SetupMain.hs, dist/setup-wrapper/Main.o ) Linking dist/setup-wrapper/setup ... ld: warning: could not create compact unwind for _ffi_call_unix64: does not use RBP or RSP based frame Cannot find gtk2hsC2hs Please install `gtk2hs-buildtools` first and check that the install directory is in your PATH (e.g. HOME/.cabal/bin). cabal: Error: some packages failed to install: glib-0.12.2 failed during the configure step. The exception was: ExitFailure 1 ------- I've tried cabal install gtk2hs-buildtools, and appears to complete (it does have two compilation warnings), but that doesn't help. Any suggestions? Victor Miller Here's the result cabal install gtk2hs-buildtools: bash-3.2$ sudo cabal install gtk2hs-buildtools Resolving dependencies... Configuring gtk2hs-buildtools-0.12.1... Preprocessing executables for gtk2hs-buildtools-0.12.1... Building gtk2hs-buildtools-0.12.1... [1 of 2] Compiling Paths_gtk2hs_buildtools ( dist/build/autogen/Paths_gtk2hs_buildtools.hs, dist/build/gtk2hsTypeGen/gtk2hsTypeGen-tmp/Paths_gtk2hs_buildtools.o ) [2 of 2] Compiling Main ( hierarchyGen/TypeGen.hs, dist/build/gtk2hsTypeGen/gtk2hsTypeGen-tmp/Main.o ) Linking dist/build/gtk2hsTypeGen/gtk2hsTypeGen ... ld: warning: could not create compact unwind for _ffi_call_unix64: does not use RBP or RSP based frame [1 of 2] Compiling Paths_gtk2hs_buildtools ( dist/build/autogen/Paths_gtk2hs_buildtools.hs, dist/build/gtk2hsHookGenerator/gtk2hsHookGenerator-tmp/Paths_gtk2hs_buildtools.o ) [2 of 2] Compiling Main ( callbackGen/HookGenerator.hs, dist/build/gtk2hsHookGenerator/gtk2hsHookGenerator-tmp/Main.o ) Linking dist/build/gtk2hsHookGenerator/gtk2hsHookGenerator ... ld: warning: could not create compact unwind for _ffi_call_unix64: does not use RBP or RSP based frame [ 1 of 41] Compiling DLists ( c2hs/base/general/DLists.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/DLists.o ) dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CLexer.hs:1:12: Warning: -fglasgow-exts is deprecated: Use individual extensions instead [ 2 of 41] Compiling BaseVersion ( c2hs/base/admin/BaseVersion.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/BaseVersion.o ) [ 3 of 41] Compiling Switches ( c2hs/state/Switches.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/Switches.o ) [ 4 of 41] Compiling Map ( c2hs/base/general/Map.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/Map.o ) [ 5 of 41] Compiling FastMutInt ( c2hs/base/general/FastMutInt.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/FastMutInt.o ) [ 6 of 41] Compiling Config ( c2hs/base/admin/Config.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/Config.o ) [ 7 of 41] Compiling C2HSConfig ( c2hs/toplevel/C2HSConfig.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/C2HSConfig.o ) [ 8 of 41] Compiling CInfo ( c2hs/gen/CInfo.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CInfo.o ) [ 9 of 41] Compiling Version ( c2hs/toplevel/Version.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/Version.o ) [10 of 41] Compiling Binary ( c2hs/base/general/Binary.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/Binary.o ) [11 of 41] Compiling Position ( c2hs/base/general/Position.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/Position.o ) [12 of 41] Compiling UNames ( c2hs/base/general/UNames.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/UNames.o ) [13 of 41] Compiling Errors ( c2hs/base/errors/Errors.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/Errors.o ) [14 of 41] Compiling Attributes ( c2hs/base/syms/Attributes.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/Attributes.o ) [15 of 41] Compiling Idents ( c2hs/base/syms/Idents.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/Idents.o ) [16 of 41] Compiling CTokens ( c2hs/c/CTokens.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CTokens.o ) [17 of 41] Compiling CAST ( c2hs/c/CAST.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CAST.o ) [18 of 41] Compiling CPretty ( c2hs/c/CPretty.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CPretty.o ) [19 of 41] Compiling Lexers ( c2hs/base/syntax/Lexers.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/Lexers.o ) [20 of 41] Compiling StateTrans ( c2hs/base/state/StateTrans.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/StateTrans.o ) [21 of 41] Compiling StateBase ( c2hs/base/state/StateBase.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/StateBase.o ) [22 of 41] Compiling NameSpaces ( c2hs/base/syms/NameSpaces.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/NameSpaces.o ) [23 of 41] Compiling CAttrs ( c2hs/c/CAttrs.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CAttrs.o ) [24 of 41] Compiling CBuiltin ( c2hs/c/CBuiltin.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CBuiltin.o ) [25 of 41] Compiling CParserMonad ( c2hs/c/CParserMonad.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CParserMonad.o ) [26 of 41] Compiling CLexer ( dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CLexer.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CLexer.o ) dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CLexer.hs:454:17: Warning: Bindings containing unlifted types should use an outermost bang pattern: base = alexIndexInt32OffAddr alex_base s In the expression: let base = alexIndexInt32OffAddr alex_base s (I# (ord_c)) = ord c offset = (base +# ord_c) .... in case new_s of { -1# -> (new_acc, input) _ -> alex_scan_tkn user orig_input (len +# 1#) new_input new_s new_acc } In a case alternative: Just (c, new_input) -> let base = alexIndexInt32OffAddr alex_base s (I# (ord_c)) = ord c .... in case new_s of { -1# -> (new_acc, input) _ -> alex_scan_tkn user orig_input (len +# 1#) new_input new_s new_acc } In the second argument of `seq', namely `case alexGetChar input of { Nothing -> (new_acc, input) Just (c, new_input) -> let base = ... .... in case new_s of { -1# -> ... _ -> alex_scan_tkn user orig_input (len +# 1#) new_input new_s new_acc } }' dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CLexer.hs:455:17: Warning: Bindings containing unlifted types should use an outermost bang pattern: (I# (ord_c)) = ord c In the expression: let base = alexIndexInt32OffAddr alex_base s (I# (ord_c)) = ord c offset = (base +# ord_c) .... in case new_s of { -1# -> (new_acc, input) _ -> alex_scan_tkn user orig_input (len +# 1#) new_input new_s new_acc } In a case alternative: Just (c, new_input) -> let base = alexIndexInt32OffAddr alex_base s (I# (ord_c)) = ord c .... in case new_s of { -1# -> (new_acc, input) _ -> alex_scan_tkn user orig_input (len +# 1#) new_input new_s new_acc } In the second argument of `seq', namely `case alexGetChar input of { Nothing -> (new_acc, input) Just (c, new_input) -> let base = ... .... in case new_s of { -1# -> ... _ -> alex_scan_tkn user orig_input (len +# 1#) new_input new_s new_acc } }' dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CLexer.hs:456:17: Warning: Bindings containing unlifted types should use an outermost bang pattern: offset = (base +# ord_c) In the expression: let base = alexIndexInt32OffAddr alex_base s (I# (ord_c)) = ord c offset = (base +# ord_c) .... in case new_s of { -1# -> (new_acc, input) _ -> alex_scan_tkn user orig_input (len +# 1#) new_input new_s new_acc } In a case alternative: Just (c, new_input) -> let base = alexIndexInt32OffAddr alex_base s (I# (ord_c)) = ord c .... in case new_s of { -1# -> (new_acc, input) _ -> alex_scan_tkn user orig_input (len +# 1#) new_input new_s new_acc } In the second argument of `seq', namely `case alexGetChar input of { Nothing -> (new_acc, input) Just (c, new_input) -> let base = ... .... in case new_s of { -1# -> ... _ -> alex_scan_tkn user orig_input (len +# 1#) new_input new_s new_acc } }' dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CLexer.hs:457:17: Warning: Bindings containing unlifted types should use an outermost bang pattern: check = alexIndexInt16OffAddr alex_check offset In the expression: let base = alexIndexInt32OffAddr alex_base s (I# (ord_c)) = ord c offset = (base +# ord_c) .... in case new_s of { -1# -> (new_acc, input) _ -> alex_scan_tkn user orig_input (len +# 1#) new_input new_s new_acc } In a case alternative: Just (c, new_input) -> let base = alexIndexInt32OffAddr alex_base s (I# (ord_c)) = ord c .... in case new_s of { -1# -> (new_acc, input) _ -> alex_scan_tkn user orig_input (len +# 1#) new_input new_s new_acc } In the second argument of `seq', namely `case alexGetChar input of { Nothing -> (new_acc, input) Just (c, new_input) -> let base = ... .... in case new_s of { -1# -> ... _ -> alex_scan_tkn user orig_input (len +# 1#) new_input new_s new_acc } }' dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CLexer.hs:459:17: Warning: Bindings containing unlifted types should use an outermost bang pattern: new_s = if (offset >=# 0#) && (check ==# ord_c) then alexIndexInt16OffAddr alex_table offset else alexIndexInt16OffAddr alex_deflt s In the expression: let base = alexIndexInt32OffAddr alex_base s (I# (ord_c)) = ord c offset = (base +# ord_c) .... in case new_s of { -1# -> (new_acc, input) _ -> alex_scan_tkn user orig_input (len +# 1#) new_input new_s new_acc } In a case alternative: Just (c, new_input) -> let base = alexIndexInt32OffAddr alex_base s (I# (ord_c)) = ord c .... in case new_s of { -1# -> (new_acc, input) _ -> alex_scan_tkn user orig_input (len +# 1#) new_input new_s new_acc } In the second argument of `seq', namely `case alexGetChar input of { Nothing -> (new_acc, input) Just (c, new_input) -> let base = ... .... in case new_s of { -1# -> ... _ -> alex_scan_tkn user orig_input (len +# 1#) new_input new_s new_acc } }' [27 of 41] Compiling FNameOps ( c2hs/base/general/FNameOps.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/FNameOps.o ) [28 of 41] Compiling FileOps ( c2hs/base/general/FileOps.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/FileOps.o ) [29 of 41] Compiling CIO ( c2hs/base/state/CIO.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CIO.o ) [30 of 41] Compiling State ( c2hs/base/state/State.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/State.o ) [31 of 41] Compiling C2HSState ( c2hs/state/C2HSState.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/C2HSState.o ) [32 of 41] Compiling CHSLexer ( c2hs/chs/CHSLexer.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CHSLexer.o ) [33 of 41] Compiling CHS ( c2hs/chs/CHS.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CHS.o ) [34 of 41] Compiling GenHeader ( c2hs/gen/GenHeader.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/GenHeader.o ) [35 of 41] Compiling CTrav ( c2hs/c/CTrav.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CTrav.o ) [36 of 41] Compiling CNames ( c2hs/c/CNames.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CNames.o ) [37 of 41] Compiling CParser ( dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CParser.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/CParser.o ) [38 of 41] Compiling C ( c2hs/c/C.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/C.o ) [39 of 41] Compiling GBMonad ( c2hs/gen/GBMonad.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/GBMonad.o ) [40 of 41] Compiling GenBind ( c2hs/gen/GenBind.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/GenBind.o ) [41 of 41] Compiling Main ( c2hs/toplevel/Main.hs, dist/build/gtk2hsC2hs/gtk2hsC2hs-tmp/Main.o ) Linking dist/build/gtk2hsC2hs/gtk2hsC2hs ... ld: warning: could not create compact unwind for _ffi_call_unix64: does not use RBP or RSP based frame Warning: No documentation was generated as this package does not contain a library. Perhaps you want to use the --executables flag. Installing executable(s) in /Users/victorsmiller/Library/Haskell/ghc-7.0.4/lib/gtk2hs-buildtools-0.12.1/bin Updating documentation index /Users/victorsmiller/Library/Haskell/doc/index.html

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Thanks and a happy new year!
by Ertugrul Söylemez 01 Jan '12

01 Jan '12

Dear fellow Haskellers, as I have learned so much throughout the past four years of Haskell experience, I feel obligated to thank everyone for the nice support and the great ideas. Exploring and using Haskell has changed my way of thinking about programming and computers in a profound way and made me a lot more productive. A happy new year 2012 for Haskell hacking to everyone! Many greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://ertes.de/

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Twidge using hashtags
by Martin de Bruin 31 Dec '11

31 Dec '11

Hello! fairly new to twidge. Got it installed and have it setting status etc etc . I'm maintaing a local website supporting the eating of a seasonal pastry in a highly competitve fashion. A race of sorts. The contestant eating the most from january first to good friday wins. To keep the eating as transparent as possible one must report each pastry on the web. However, I feel this is not very 2012. I'm thinking about going about the new version allowing reporting to be done via twitter and picking it up with Twidge. To keep everything as much in the open as possible I'd like to have all contestants twittering the eating of a pastry mentioning the "official twitter account of the website" and throw in a hashtag like #report and then some comment. I'll then read the feed periodically via cron on the server and update the highscore database. Am I making sense? The longer I typed the above the more I started thinkng about just doing something in PHP... Any thoughts? Cheers Martin

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Plugins on ghc 7.2: GHC does not export defaultCallbacks
by Brian Victor 31 Dec '11

31 Dec '11

Hi all, As a getting-my-feet-wet project I was starting to look into using plugins-auto with the yesod devel server, but I was quickly stymied because the plugins package isn't building on GHC 7.2. The error I get locally is the same as the one reported by hackage[1]. In short, defaultCallbacks seems to be gone from 7.2. It doesn't look like that function has simply been moved. So can someone give me an idea about how to proceed? Thanks! [1] http://hackage.haskell.org/packages/archive/plugins/1.5.1.4/logs/failure/gh… -- Brian

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Copy .cabal folder to diff machine/user
by Vagif Verdi 31 Dec '11

31 Dec '11

Is it possible to copy .cabal and .ghc folders to different machine/ user and develop same project over there ? Or is the only way to allow a team of developers to work on the same project is to force each one of them to install all necessary packages on their machines.

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Level of Win32 GUI support in the Haskell platform
by Steve Horne 31 Dec '11

31 Dec '11

I've been for functions like GetMessage, TranslateMessage and DispatchMessage in the Haskell Platform Win32 library - the usual message loop stuff - and not finding them. Hoogle says "no results found". Is this level of Win32 GUI coding supported? (other than by dealing with the FFI myself) Alternatively, should I be doing dialog-based coding and leaving Haskell to worry about message loops behind the scenes? Either way, is there an example I can use for reference? I have something along the lines of Petzolds Hello World in mind as the ideal (register a window class, handle the messages, paint some text), but anything that shows how to get a basic Win32 GUI app running in Haskell is fine.

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