November 2008 - Haskell-Cafe

Cabal and more than one version
by Jason Dusek 03 Feb '09

03 Feb '09

I'd like to be able to do something like: if (template-haskell < 2.3) cpp-options: -D TH_THE_YOUNGER else cpp-options: -D TH_THE_ELDER I guess this kind of thing is not possible at present? -- _jsn

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Re: Haskell on ARM (was Re: ANN: Topkata)
by Jeremy Apthorp 30 Jan '09

30 Jan '09

2008/6/25 Braden Shepherdson <Braden.Shepherdson(a)gmail.com>: > Jeremy Shaw wrote: >> >> If any does attempt to build for the ARM, please, please, please, >> document what you do in the wiki. And, if you do, edit the wiki as you >> go, you definitely won't be able to remember what you did after the >> fact. (Or, at the very least, use some program to capture everything >> you do so that you can refer to it later). >> >> And, finally, I heard vague rumors a while ago that made me think that >> GHC 6.10 might have a pure ANSI-C backend? Is there any truth to this? >> That would make porting much easier if it meant you did not have to do >> steps 1-4. >> >> j. >> ps. I would be happy to try to answer any questions if someone tries a >> port. I would still like to run GHC on my 770, and I hope to own an >> iPhone if they fix a few ommisions (bluetooth keyboard support, and >> similar stuff). >> > > > I recently acquired the ARM-based Nokia N810 (and <3 it), powered by Maemo. > Running a uname -a on it: > > Linux Nokia-N810-42-19 2.6.21-omap1 #2 Fri Nov 16 16:24:58 EET 2007 armv6l > unknown > > I would love a working GHC implementation on it, if for nothing else than > how awesome it would be. Whether that means using a C back-end or native > compilation doesn't matter to me so much. > > I might be one to attempt this, as I know C and ARM-ish asm decently well > and have a powerful desktop to compile on. I have no familiarity > with GHC internals, though. Lastly, I won't have anything like the time to > attempt this seriously until mid-September or so. Oops, forgot to Cc the list. Next year I'll be working on a project for my undergraduate computing course at UNSW that will involve getting GHC to target the Nintendo DS. It'll require cross-compilation, because the DS isn't powerful enough to actually run GHC (4M main ram and a 66MHz processor). It'll also require that I significantly strip down the runtime system, as the current RTS won't fit in 4M and leave any left over for the main application. I'll be documenting the whole process, but I won't be starting until next year... Jeremy

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Re: Compiling regex-posix-0.93.2 on windows
by Chris Kuklewicz 17 Jan '09

17 Jan '09

I am not sure what is going wrong. I have not been using Haskell on windows. I am also copying this reply to haskell-cafe and libaries mailing lists. Does anyone know? Parnell Flynn wrote: > I am having a terrible time compiling the 0.93.2 version of the > regex-posix library on windows XP. > > I have Cygwin and MinGW installed and I have a version of the regex.h > header in C:/cygwin/usr/include what shared libraries do I need? > > Here is a copy of the error it finds the include but is unable to link. > > This links to the standard c library version of regular expressions. > > The corresponding c header file is regex.h and there is a chance you > > will need to edit the end of the regex-posix.cabal file to find the > > include directory and/or library. > > Preprocessing library regex-posix-0.93.2... > > dist/build/Text/Regex/Posix/Wrap_hsc_make.o(.text+0x85):Wrap_hsc_make.c: > undefined reference to `_impure_ptr' > > dist/build/Text/Regex/Posix/Wrap_hsc_make.o(.text+0xc9):Wrap_hsc_make.c: > undefined reference to `_impure_ptr' > > dist/build/Text/Regex/Posix/Wrap_hsc_make.o(.text+0xf1):Wrap_hsc_make.c: > undefined reference to `_impure_ptr' > > dist/build/Text/Regex/Posix/Wrap_hsc_make.o(.text+0x125):Wrap_hsc_make.c: > undefined reference to `_impure_ptr' > > dist/build/Text/Regex/Posix/Wrap_hsc_make.o(.text+0x159):Wrap_hsc_make.c: > undefined reference to `_impure_ptr' > > dist/build/Text/Regex/Posix/Wrap_hsc_make.o(.text+0x18d):Wrap_hsc_make.c: > more undefined references to `_impure_ptr' follow > > collect2: ld returned 1 exit status > > linking dist\build\Text\Regex\Posix\Wrap_hsc_make.o failed > > command was: y:\ghc\ghc-6.8.2\bin\ghc.exe -optl-LC:/cygwin/lib > dist\build\Text\Regex\Posix\Wrap_hsc_make.o -o > dist\build\Text\Regex\Posix\Wrap_hsc_make.exe > > bash-3.2$ > > Thanks, > > Parnell > > Parnell Flynn • 230 South Lasalle Street • Suite 400 • Chicago, IL 60604 > • 312.244.5317 (o) • parnell___.flynn(a)ronin-capital.com_ > <mailto:parnell.flynn@ronin-capital.com> >

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ANNOUNCE: gitit 0.2 release - wiki using HAppS, git, pandoc
by John MacFarlane 16 Jan '09

16 Jan '09

I've uploaded an early version of gitit, a Haskell wiki program, to HackageDB. Gitit uses HAppS as a webserver, git for file storage, pandoc for rendering the (markdown) pages, and highlighting-kate for highlighted source code. Some nice features of gitit: - Pages and uploaded files are stored in a git repository and may be added, deleted, and modified directly using git. - Pages may be organized into subdirectories. - Pandoc's extended version of markdown is used, so you can do tables, footnotes, syntax-highlighted code blocks, and LaTeX math. (And you can you pandoc to convert pages into many other formats.) - Math is rendered using jsMath (which must be installed separately). - Source code files in the repository are automatically rendered with syntax highlighting (plain/text version is also available). You can check it out on my webserver: http://johnmacfarlane.net:5001/ Or try it locally: cabal update cabal install pandoc -fhighlighting cabal install gitit gitit # note: this will create two subdirectories in the working directory # then browse to http://localhost:5001. There's a git repository at http://github.com/jgm/gitit/tree/master. Comments and patches are welcome. John

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Haskell, successing crossplatform API standart
by Belka 04 Jan '09

04 Jan '09

Hello! (1) Is anybody aware of SOA approach being supported in Haskell? Found HAIFA package (SOAP, WEB services), but it seems to be a RIP project (with it's last updated in 2006) - trying to install it is a total mess (for me, a newby). (2) Please, perhaps experienced developers could suggest any better crossplatform (crosslanguage) API standart supported in Haskell? For me the main priority is orientation on "being supported everywhere in far future"... Thanks in advance -- View this message in context: http://www.nabble.com/Haskell%2C-successing-crossplatform-API-standart-tp20… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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Windows vs. Linux x64
by Bartosz Wójcik 21 Dec '08

21 Dec '08

Hi Everybody, while working on my resent project I've noticed that my code seems to be faster under Windows than under Linux x64. More exactly this was an AI game evaluator that ran on given parameters. There was no IO performed. I've run 3 lots of test on both systems and stored some figures. It was physicaly the same PC. 1st lot WinXP total time = 27.18 secs (1359 ticks @ 20 ms) total alloc = 5,788,242,604 bytes (excludes profiling overheads) Linux total time = 34.44 secs (1722 ticks @ 20 ms) total alloc = 11,897,757,176 bytes (excludes profiling overheads) 2nd lot WinXP total time = 63.96 secs (3198 ticks @ 20 ms) total alloc = 13,205,507,148 bytes (excludes profiling overheads) Linux total time = 80.76 secs (4038 ticks @ 20 ms) total alloc = 27,258,694,888 bytes (excludes profiling overheads) 3rd lot WinXP total time = 207.10 secs (10355 ticks @ 20 ms) total alloc = 44,982,716,780 bytes (excludes profiling overheads) Linux total time = 267.58 secs (13379 ticks @ 20 ms) total alloc = 92,307,482,416 bytes (excludes profiling overheads) I've used the same compile and runtime options for both. I've tried to run with -H option, but this didn't improve anything. Is this common behaviour? Does anybody know what can be the reason? regards, Bartek

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Line noise
by Andrew Coppin 21 Dec '08

21 Dec '08

I hang out on another forum that is populated by various kinds of computer geeks. There's a fair few programmers in there, as well as nerds of every degree. And yet, every time I post anything written in Haskell, everybody complains that it "looks like line noise". What do "normal" programmers find so puzzling about Haskell? You might guess some of the following: - High-order functions. - Lambda functions. - Algebraic data types. - Lazy evaluation. - Recursion. - Monads. Actually, none of these things were mentioned. The things people have *actually* complained to me about are: - Haskell expressions are difficult to parse. - Several standard library elements have unhelpful names such as "elem", "Eq" and "fst". (My favourite has to be "Ix". I mean, WTH?) - Several standard library functions have names which clash badly with the usual meanings of those names - e.g., "break", "return", "id". - Variable names such as "x" and "f" aren't fabulously helpful to lost programmers trying to find their way. If you take a "typical" lump of C or Java code, there's so much redundancy and noise in it that you can *usually* figure out vaguely what's going on, even if it doesn't completely make sense. When presented with a typical Haskell fragment... uh... well, good luck with that. Let's take Haskell's most celebrated example: qsort [] = [] qsort (x:xs) = qsort (filter (x <) xs) ++ [x] ++ qsort (filter (x >=) xs) To a novice, it's not actually real clear what the arguments to qsort are. You and I know that function application binds much more tightly than (++), but a novice isn't going to know that. You might also not immediately realise that "xs" is also an argument to filter, not just (x <) or whatever. The people I spoke to also seemed pretty confused about the usage of (.) and ($), even after I explained it a few times. Several people also voiced being puzzled about Haskell's layout rules. I'm not sure what we *do* with all this data, but I found it interesting so I thought I'd share. ;-) I've spent the last few years trying to convert a few people to The Haskell Way(tm), but so far I haven't succeeded in the slightest. I just get yelled at for pointing white noise. Heh. Oh well!

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Reader monad, implicit parameters, or something else altogether?
by Bjorn Buckwalter 16 Dec '08

16 Dec '08

All, I have a growing amount of astrodynamics code that relies on various physical "constants". The problem with these so called "constants" are that they either aren't really constants or aren't well known. An example is the leap second table (see Data.Time.Clock.TAI). I'd like to be able to fetch current values of these constants at runtime and make them accessible to my astrodynamics functions by some means. To clarify, once initialized the constants will be considered constant for the remainder of the program. I'd store the constants in a data structure along the lines of: > data AstroData a = AstroData > { mu_Earth :: GravitationalParameter a > , leapSeconds :: LeapSecondTable > } I would like to know if there is any consensus on what is the best way to make such a data structure accessible in pure functions. Passing it explicitly would be a mess. It seems that two options are to use either a Reader monad or implicit parameters. Using a Reader monad is straight forward enough though it requires writing/converting code in/to monadic style and adds some clutter to the formulae. It seems implicit parameters could be cleaner but I've seen them referred to as everything from evil to "just what you need" and rendering the Reader monad obsolete... What do you people recommend? Thanks, Bjorn Buckwalter

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Problem with haddock 2.3.0 (again)
by Leonidas Fegaras 15 Dec '08

15 Dec '08

Sorry for the previous message. I am sending it again. Dear fellow haskell programmers, I tried to install a package in hackageDB and got a strange error from haddock: haddock: internal Haddock or GHC error: Maybe.fromJust: Nothing Here is the complete log: http://hackage.haskell.org/packages/archive/HXQ/0.10.0/logs/failure/ghc-6.8 When I build it using Cabal 1.6.0.1 and haddock 2.2.2 using 'runhaskell Setup.lhs haddock', it works fine (I get warnings but no errors). Also haddock 2.3.0 is not available in hackageDB so I can't test it myself. Where I can find haddock 2.3.0? Thank you for your help, Leonidas Fegaras _________________________________________________________________ Stay organized with simple drag and drop from Windows Live Hotmail. http://windowslive.com/Explore/hotmail?ocid=TXT_TAGLM_WL_hotmail_102008

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Data.Array.Storable vs GC
by David F. Place 12 Dec '08

12 Dec '08

If you have a giant unboxed array that will never become garbage, it would be nice to put it somewhere where the GC won't bother with it. Since Data.Array.Storable arrays are allocated in the C heap, I thought it would be a good choice. However, I am getting very poor performance due to the GC copying 6G in each run. The only explanation that I can think of is that it is copying my giant array. Am I wrong in my understanding that Data.Array.Storable arrays should not be copied by the GC? BTW, I am using GHC 6.10.1 on linux. Thanks for reading.

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