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RE: [Haskell-cafe] What Functions are Standard?
by Simon Peyton-Jones 07 Oct '04

07 Oct '04

John | > I have been writing code using the docs over at | > http://www.haskell.org/ghc/docs/latest/html/libraries/index.html, which | > is the only comprehensive library reference I could find. | > | > I am using some code from System.IO, supposedly from base. When I try | > to build this with nhc98, it doesn't know about hGetBuf, hPutBuf, or | > openBinaryFile from there or about mallocForeignPtrArray from the | > Foreign.* area. But all these look standard to me. This is the GHC library documentation, but Hugs and NHC use the same source-code repository, but omitting some functionality. What's omitted is explicitly documented, at the exact link you give above, under "Implementation-specific notes". The language definition for Haskell 98 defines a small collection of libraries, standardised a long time ago. But all implementations come with a much richer set of libraries, many of which are written in Haskell 98, and almost all of which are usable by Haskell 98 programs. These are the ones documented above. Meanwhile lots of people are writing libraries too. In particular, there are several libraries around for reading and writing binary files, and a long recent email thread on the subject. What I'm hoping is that someone, or a small group, will decide on a good interface (in the light of experience thus far) and implement it, so that the rest of us don't have to choose. Simon

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Can I determin the function name passed in?
by Mark Carter 07 Oct '04

07 Oct '04

I'm an utter noob to Haskell, and FP in gnereal. I would like to create a function taking an argument which is a function (actually an equation taking no args, but dependent on other equations), which prints the name of the function and and it's result. Is there a way of doing this in Haskell? Sounds like a job for macros, or some kind of introspection-type stuff.

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Re: [Haskell-cafe] Re: OCaml list sees abysmal Language Shootout results
by MR K P SCHUPKE 07 Oct '04

07 Oct '04

Well, the sootout itself is using GHC, as it lists both language and implementation. There is no entry for NHC or Hugs... So I would say if the GHC specific code is neat and fast put it in... If people hant to see a NHC then there should be a separate implentation of haskell (for example I can see at least 3 schemes in the sootout) Keean.

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Re: [Haskell-cafe] Re: OCaml list sees abysmal Language Shootout results
by MR K P SCHUPKE 07 Oct '04

07 Oct '04

looking at ghc's scores... this would seem to be the next candidate for a rework: -- $Id: reversefile.ghc.html,v 1.6 2004/10/03 00:44:58 bfulgham Exp $ -- http://www.bagley.org/~doug/shootout/ -- from Julian Assange main = interact $ unlines . reverse . lines Compare this with the gcc implementation which uses buffers and is 68 lines long! Keean.

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Re: [Haskell-cafe] Re: OCaml list sees abysmal Language Shootout results
by MR K P SCHUPKE 07 Oct '04

07 Oct '04

Also, its nice to see GHC ahead of Java now in the standard results... Would be nice to beat OCaml & Clean though ... Keean.

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Integrating Haskell into a J2EE environment
by Bhinderwala, Shoeb 07 Oct '04

07 Oct '04

Hi All, I am new to Haskell and this mailing list. We have a system that uses a custom high-level language to express high-level business rules. Expressions in the high-level language get compiled to Java bytecode. We express the grammar using BNF notation as required by the javacc parser tool. This is then converted to an AST using jjtree and from there we build the final Java code. Our language could be considered a domain-specific language (DSL) and is used by our business users to express very high-level business logic. The language currently is very limited - we support boolean logic, function invocations and if-then statements. We want to convert it into a more powerful scripting language so that even lower level business logic can be expressed in it. I came across a few papers that talk about writing a DSL with Haskell as the underlying support language. How is this done. Is it possible to create a sort of domain specific business scripting language easily. How does that then compile to Haskell code. And how can the Haskell code be invoked from Java. Essentially, I am thinking if I could use a Haskell like DSL language to express our business rule logic and then be able to integrate into and invoke the logic from a J2EE app server environment. Has anybody done anything like this with Haskell. -- Shoeb

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Asteroids game, (was Space leaks)
by Ben Lippmeier 07 Oct '04

07 Oct '04

Andy, For the asteroids game, I just call GHC's System.Mem.performGC every frame and it seems to run ok. It's a very simple game, my 2.6Ghz P4 system walks all over it and the FPS counter seems to bounce around from about 150 to 300. I would imagine it's spending all it's time in the big XFillRectangle call I'm using to blank the screen, and without double buffering it flickers pretty bad. I wrote the game as a way to get some non-tree-processing experience with Haskell, and to test out a C struct marshalling FFI preprocessor I was messing with. All the graphics stuff is written using straight Xlib, called from Haskell. You're more than welcome to the code if you think you can do something with it. You can get it from my homepage at http://cs.anu.edu.au/people/Ben.Lippmeier There's also a mandelbrot set plotter, written in Haskell, which I wrote to try out various unboxing schemes. The only other (reasonably current) real-time projects i've heard of are: * The HOpenGL effort and Haskell Quake. HOpenGL seems to be somewhat active, you might like to try out some of their sample programs. I tried to get Haskell Quake to work once, but from memory they were using an ancient version of Greencard/HOpenGL for their FFI, which I couldn't get to work. The Haskell Quake home page says it hasn't been updated since 1997. * Alastair Reid's real-time computer computer vision project, FVision. http://www.reid-consulting-uk.ltd.uk/alastair/ I think they solved their Garbage Collection stall problem the same way I did, just invoked the garbage collector some fixed number of times per second / frame.. Don't know much about it, best ask him directly. * The Haskell DSP libraries http://haskelldsp.sourceforge.net/ I think its mostly an off-line, don't-care-too-much-about-runtime -performance kind of thing. I think it consists of a collection of (typically) list to list functions, so its not really designed for real time operation. However, a while back I had the idea that if you wanted to burn some CPU cycles in a real-time way, you might try piping to/from /dev/dsp with a full duplex souncard to make yourself some sort of poor-mans effect processor. Thats it. Not much code deployed out in the 'world' it seems. My PhD project is also aligned with addressing this issue. I think it's one of those catch 22 situations where no-one has written real-time programs in Haskell cause they knew it probably wouldn't work.. So when someone comes up with a new language feature which tries to solve the problem, there's no programs to try it on cause no-one's written any. Do you know of any other real-time type projects besides these? Perhaps the two of us, and who ever else is interested, should choose some real-time program (perhaps the asteroids game, or revive Haskell Quake) and spend some small, fixed amount of time per week working on it so we'll all have some application to showcase our glorious new language features with? Ben. Andrew Cheadle wrote: > Hi Ben > > >>-> An astroids game I wrote for X. >>The state: position, velocities of ship, astroids, missiles. >>The [x] list: ship control data, key codes. >>The [y] list: a list of graphics prims which get rendered to the screen. > > > I wonder if you could help me out. I'm trying to investigate the > practical use of my incremental collector for GHC over the standard > generational collector. I'm looking for applications that have soft-real > time constraints / interactive nature where garbage collector pauses are > noticable. Do you know of any such applciations, did your asteroids game > suffer any such problems? Although graphical programs would be great, > when written in Haskell the rendering engine is usually in C so they're > not usually appropriate! > > Any help greatly appreciated! > > Cheers > > Andy >

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500 great lines of Haskell code?
by Isaac Jones 07 Oct '04

07 Oct '04

This might be an interesting way to highlight the beauty and brevity of Haskell. Has anyone written a great 500-line Haskell program they want to submit? peace, isaac http://developers.slashdot.org/article.pl?sid=04/10/06/1530218&tid=156&tid=8 "Be part of the Open Source Annual 2005 and enter our hacker contest for the best 500-line open source program. The best program will be printed in next year's issue of the book. Following lasts year's huge success with our Open Source Annual, a mostly German reader concerned with the various aspects of open source, we are currently busy compiling the second edition of the annual which will be released next March for the CeBIT 2005 in Hannover. Aside from articles on subjects like economics, law and open innovation, to name but a few, we plan to print the source code of an open source software program."

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Re: [Haskell-cafe] Integrating Haskell into a J2EE environment
by Paul Hudak 07 Oct '04

07 Oct '04

Ok, I understand. I don't know much at all about J2EE, in fact! I would just hate to see an interesting project be abandoned if all that is needed is a simple way to invoke the Haskell code with a string argument, say. Perhaps Shoeb can tell us more about what he needs. -Paul Doug Kirk wrote: > Yes, I agree, and didn't mean to write off Haskell (at which, I'm > completely a newbie, trying to learn, and thankful for your book!). > > However, I'm a Java pro, and there are many technical issues on the Java > side that scream at me to keep out of the native arena, especially in a > J2EE container environment, where funny things can happen with hot > reloads (dumping old ClassLoaders for new ones), clustering, and the like. > > So it wasn't out of denigration of Haskell that I made my > recommendation; far from it...from what I've seen Haskell is perfect for > implementing DSL's. Rather, from the Java side is where it becomes > problematic. There have been many problems integrating with native > libraries from within a J2EE container, and I try to seek the most > cost-effective way (I'm an independent consultant) to get the problem > solved for my customers. > > --doug > > On Oct 6, 2004, at 2:59 PM, Paul Hudak wrote: > > I wouldn't write off Haskell so quickly. All of what Shoeb describes > concerning DSL issues might be much more easily solved in Haskell, and > will certainly be more flexible than a hard-wired approach. The J2EE > interface might be ugly, but if the functionality needed is not too > great it might not be too bad. Generally speaking, these kinds of apps > -- in this case "a DSL for high-level business rules" -- sounds like > just the sort of thing that Haskell is good for. > > -Paul

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What Functions are Standard?
by John Goerzen 06 Oct '04

06 Oct '04

Hello, I have been writing code using the docs over at http://www.haskell.org/ghc/docs/latest/html/libraries/index.html, which is the only comprehensive library reference I could find. I am using some code from System.IO, supposedly from base. When I try to build this with nhc98, it doesn't know about hGetBuf, hPutBuf, or openBinaryFile from there or about mallocForeignPtrArray from the Foreign.* area. But all these look standard to me. What am I missing here? Does nhc98 really completely lack the ability to read binary data from a file? Or where should I be finding it, and how could I have known for myself that those particular ghc functions were unsupported elsewhere? -- John Goerzen Author, Foundations of Python Network Programming http://www.amazon.com/exec/obidos/tg/detail/-/1590593715

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