- Haskell-Cafe - Haskell.org

Web server libraries
by John Goerzen 28 Mar '08

28 Mar '08

Hi again, I'm currently working on a project that has a Web interface to data stored in a SQL database. I wrote this thing in WASH a few years back. Overall, this has been acceptable, but the non-Haskell-adepts around here run away screaming from the code. Not only that, but we don't get control over the names of the form elements, which can make interacting with other software that sometimes plonks users down halfway through the process -- well, interesting. Also, WASH supports nothing better than CGI, which is a big minus when talking to SQL databases. What I really want is some sort of simple tool that supports FastCGI or some such, has basic support for form data input validation and marshalling to/from Haskell types, and basic control flow. I don't need, or really particularly want, something that uses hs-plugins to compile pages on demand (I'm using Haskell for it's static safety, after all). Nor do I need fancy templating systems or session support (we use HTTP auth and are fine with it for now.) So I've looked around a bit at the landscape. Any recommendations? I've found these: HSP: big on "dynamic pages". I don't want to make my webserver able to compile Haskell code. Develop code, compile, test, make sure it's right, then push to production every 6 months around here. WASH: Pretty much the right niche, but the event model is hard to use. HAppS: Frankly it is a big collection of confusing packages to me. What documentation exists doesn't seem to be relevant anymore, and it seems to be designed to not use a SQL database. FastCGI: Relies upon CGI for a good part of processing. Does not seem to have any form data validation support built in. Thanks again, -- John

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reactive programming, what's hot?
by Greg Fitzgerald 27 Mar '08

27 Mar '08

A new version of yampa<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Yampa-0.9.2>was uploaded to hackage today, but it's website <http://www.haskell.org/yampa/> hasn't been updated since 2004. SpaceInvaders<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/SpaceInvaders-0.…>depends on HGL and Yampa. There's been more noise around Phooey<http://haskell.org/haskellwiki/Phooey>and TV <http://haskell.org/haskellwiki/TV> in recent months, but afaik, hasn't been used for any applications yet. There was also ParseP <http://twan.home.fmf.nl/parsep/> which seems to tackle a similar problem, but from the perspective of a more general parsing library. Are there other purely functional reactive libraries in active development? Why might one choose one over another? Thanks, Greg

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GSoC Project Proposal: Parallel Profiling Tools for GHC.
by Donnie Jones 27 Mar '08

27 Mar '08

Hello Everyone,GSoC Project: Parallel Profiling Tools for GHC. Student: Donnie Jones Mentor: Simon Marlow Project based upon suggestion by Simon Marlow: http://hackage.haskell.org/trac/summer-of-code/ticket/1559 Overview: For Haskell there are currently no tools to investigate the performance of parallel programs. This project would extend the Haskell compiler GHC to support profiling of parallel programs. Parallel programs are inherently difficult to analyze and the prevalence of multi-core processors has increased the need for tools to facilitate gaining performance from parallelism. The ability to profile parallel programs in GHC could lead to improvements in GHC's RTS, and insights into writing parallel Haskell code. Goals: * Investigate the use of the GranSim framework for parallel profiling in GHC i. Decide what is needed to commit the GranSim port to the GHC tree i. Build additional profiling tools upon the GranSim framework * Testing of performance hit accrued from parallel profiling i. Investigate improving performance, possible modifications to GranSim port * Construct tests to measure the performance improvements of parallel programs i. Building benchmarks for parallel programs, related to ticket: http://hackage.haskell.org/trac/summer-of-code/ticket/1544 * Improve upon GranSim visualization of profiles to clarify parallel profiling i. Possibly add new visualization profiles, if time allows I am sure that further details will need to be developed with the help of Simon Marlow; however, I am unsure if some of these details can be defined without first investigating the potential use of GranSim. I look forward to your feedback. Thank you. __ Donnie Jones

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Terminating GLUT/GLFW programs
by hjgtuyl＠chello.nl 27 Mar '08

27 Mar '08

L.S., I am trying GLUT and GLFW (on Windows XP, with GHC 6.8.2); the sample programs do not terminate when I close the window by clicking on the cross in the upper right corner of the window. The sample program for GLUT is at http://blog.mikael.johanssons.org/archive/2006/09/opengl-programming-in-has… the GLFW program: http://haskell.org/haskellwiki/GLFW I tried in the GLUT program: close = exitWith ExitSuccess closeCallback $= Just close -- => User error (unknown GLUT call getCloseFunc, check for freeglut) this needs freeglut (not documented); I downloaded freeglut.dll and placed it in the windows\system32 directory. The error message remained. What is needed to let these programs terminate properly? -- Met vriendelijke groet, Henk-Jan van Tuyl -- http://functor.bamikanarie.com http://Van.Tuyl.eu/ --

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Libraries need a new owner
by Adrian Hey 27 Mar '08

27 Mar '08

Hello Folks, As some of you will be aware, I have been working on various Map implementations that currently live here.. http://code.haskell.org/collections/collections-ghc6.8 The libs in question being Data.Tree.AVL, Data.Trie.General and a few other bits like Data.COrdering and the AVL based Data.Map/Set clones. Well, I have decided to stop work on these. So they need a new owner if they're going to go anywhere. If anyone is interested in the job then I suggest they contact myself or Jean-Philippe Bernardy. Of course I will be happy to provide any help or advise anyone who takes over these libs may feel they need from me. I might even contribute a few patches from time to time myself :-) Thanks -- Adrian Hey

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No newlines in the whitespace for Parsec lexeme parsers
by Paul Keir 27 Mar '08

27 Mar '08

Hi, I'm looking to parse a Fortran dialect using Parsec, and was hoping to use the ParsecToken module. Fortran though is unlike the Parsec examples, and prohibits default line continuation (requiring instead an explicit ampersand token &). The lexical parsers of the ParsecToken module skip whitespace after each symbol parsed (lexeme parsers); including the newline. I was thinking of making a minor change to Parsec: In Token.hs, lexeme, whiteSpace, and simpleSpace are defined. lexeme uses whiteSpace which uses simpleSpace. simpleSpace is defined: simpleSpace = skipMany1 (satisfy isSpace) I could replace this locally with: simpleSpace = skipMany1 (satisfy isSpacePlusAmpersandMinusNewline) This approach may have other problems though. Has anyone experience of using Parsec to parse such a language? For example assembly or a preprocessor? Thanks in advance, Paul

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FW: containers-0.1.0.1
by john lask 27 Mar '08

27 Mar '08

who is maintainer of containers package ... ---------------------------------------- > From: jvlask(a)hotmail.com > To: libraries(a)haskell.org > Subject: containers-0.1.0.1 > Date: Wed, 12 Mar 2008 23:48:33 +0000 > > > > containers-0.1.0.1 will not build with ghc-6.6, the lines > #include "Typeable.h" INSTANCE_TYPEABLE1(Set,setTc,"Set") > > cause a parsing error, due no doubt to Typeable.h being different to 6.8 version > _________________________________________________________________ > What are you waiting for? Join Lavalife FREE > _________________________________________________________________ Are you paid what you're worth? Find out: SEEK Salary Centre http://a.ninemsn.com.au/b.aspx?URL=http%3A%2F%2Fninemsn%2Eseek%2Ecom%2Eau%2…

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Unboxed arrays
by Andrew Coppin 26 Mar '08

26 Mar '08

Somebody asked me, so now I'm asking you... In Haskell, you can make "unboxed" arrays of certain value types. These are typically more efficient in space, and probably time too, and also make the array strict in its values. However, you can only do this magic trick for certain types - not for *all* types. Why is that? Is it because nobody has done anything about it yet? Is it because it's thought to be "not necessary" in some way? Is there some theoretical problem? Has somebody got a better idea? I did think it was along the lines of "oh, well, if you want to unbox a type of your own, you just need to write your own instance". The thing that makes me suspicious of this logic is the absense of an instance for tuples. Surely this would be trivial to write, and yet it's not present. If we had instances for a couple of sizes of tuples, it would surely be quite easy to write your own custom instances that just sit on top of this and tuple/untuple your custom values... Any insights here?

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Type synonyms
by Hugo Pacheco 26 Mar '08

26 Mar '08

Hi guys, There is something I think not to fully understand: what are the differences between these two type synonyms? type FInt x = Either One x type FInt = Either One Their kind is the same, so do they differ or are exactly the same type? Thanks, hugo

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[GSoC] student applications deadline approaching
by Malcolm Wallace 26 Mar '08

26 Mar '08

Reply-To: haskell-cafe(a)haskell.org Just to remind students who are interested in Google Summer of Code. Student applications are now open, and the final deadline for submitting your proposals is 2400 UTC, 31st March. http://code.google.com/soc/2008/ Regards, Malcolm

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