Re: [Haskell-cafe] Foreign function Intf./GHC newbie question
Hello John, Saturday, November 26, 2005, 5:59:41 AM, you wrote: JZ I want to compile a Haskell program that calls a foreign C function. I'm JZ using GHC. When GHC links, it says it can't find my C function. That is JZ not surprising, because I can't figure out how I'm supposed to tell GHC JZ where to find my C function. in order to link in C module you should compile it separatelly (better by ghc itself - it will setup all needed options and then call gcc) and add its .o module to the cmdline: ghc -c myc.c ghc --make ffi.hs myc.o also try the following: ghc --make ffi.hs myc.c may be it will also work -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Monads in Java, Joy, OCaml, Perl, Prolog, Python, Ruby, and Scheme was Re: Other languages using monads?
Am Samstag, 26. November 2005 03:56 schrieb Geoffrey Alan Washburn: [lots of code] It's interesting to note how verbose Java is in comparison to Haskell, at least, concerning this monad stuff. Best wishes, Wolfgang ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell GUI on top of Xlib?
On Sat, 2005-11-26 at 00:17 -0500, Dimitry Golubovsky wrote: Do there exist Haskell graphics/UI toolkits implemented on top of the X11 library (Xlib) without any intermediate C/C++ libraries (i. e. not WxHaskell for example)? I have a very low level client-side interface to the X11 protocol implemented in pure Haskell (layout of protocol packets obtained from Xlib header files preprocessed by HSFFIG). As of now, I can open a display, build request packets manually and parse server responses (some of, but this is just a matter of writing more parsers), so this is more like a toolset for X11 protocol packets manipulations. I do not intend to implement a full analog of Xlib in Haskell. Instead, it might be interesting to create a fully functional GUI toolkit based on some already existing high-level interface. Any ideas will be appreciated. Are you aware of the XCB library: http://xcb.freedesktop.org/ It's a more modern client side X11 library. In particular they have a good infrastructure for describing the X11 protocol packets using XML. They use that to generate code in various languages for dealing with those packets. XCB is supposed to be simpler and more regular than Xlib and with less historical cruft. It is also supposed to support multiple threads properly (which is nearly impossible with Xlib). Indeed they mention that Haskell would be an obvious target for this: http://xcb.freedesktop.org/wiki/XCBToDo (see bottom of that page: XCB for other languages) Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Monads in Java, Joy, OCaml, Perl, Prolog, Python, Ruby, and Scheme was Re: Other languages using monads?
Wolfgang Jeltsch wrote: Am Samstag, 26. November 2005 03:56 schrieb Geoffrey Alan Washburn: [lots of code] It's interesting to note how verbose Java is in comparison to Haskell, at least, concerning this monad stuff. I'd agree. However, my original point was that my version that uses generics is still significantly less verbose than the version without. I think much of the overhead is that Java simply doesn't do as much type inference for you. Scala can do much better still because it has first-class functions and algebraic data types (case classes). ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Monads in Scala, XSLT, Unix shell pipes was Re: Monads in ...
Geoffrey Alan Washburn [EMAIL PROTECTED] writes: Scala can do much better still because it has first-class functions and algebraic data types (case classes). Comments on http://lambda-the-ultimate.org/node/view/1136 include links to Scala http://scala.epfl.ch/examples/files/simpleInterpreter.html and XSLT rumors http://www.biglist.com/lists/xsl-list/archives/200303/msg00422.html There's also Oleg's http://okmij.org/ftp/Computation/monadic-shell.html at the level of UNIX programming, all i/o can be regarded monadic. -- Shae Matijs Erisson - http://www.ScannedInAvian.com/ - Sockmonster once said: You could switch out the unicycles for badgers, and the game would be the same. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Monads in Scala, XSLT, Unix shell pipes was Re: Monads in ...
--- Shae Matijs Erisson [EMAIL PROTECTED] wrote: Geoffrey Alan Washburn [EMAIL PROTECTED] writes: There's also Oleg's http://okmij.org/ftp/Computation/monadic-shell.html at the level of UNIX programming, all i/o can be regarded monadic. Interesting. I had been thinking about I/O and operating systems as a different(?) framework for trying to explain the concept of monads: If you think about a write statement in an imperative language, it doesn't actually perform the requested operation, it just asks the OS to perform the action later. With respect to pipes, remember that files are really fictions, too, and when you write to a pipe the data is stored somewhere (most likely in memory) and then read in lazy fashion. Maybe this is a different topic, but exploring concurrency in Haskell is definitely on my to do list, but this is really a bit of a puzzle. One thing I've been thinking lately is that in functional programming the process is really the wrong abstraction (computation is reduction, not a sequence of steps performed in temporal order). But what is concurrency if their are no processes to run concurrently? I've beren thinking about action systems and non-determinism, but am unsure how the pieces really fit together. === Gregory Woodhouse [EMAIL PROTECTED] Interaction is the mind-body problem of computing. --Philip Wadler ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Dataflow and Comonads was Re: [Haskell-cafe] Monads in Scala, ...
Greg Woodhouse [EMAIL PROTECTED] writes: Maybe this is a different topic, but exploring concurrency in Haskell is definitely on my to do list, but this is really a bit of a puzzle. One thing I've been thinking lately is that in functional programming the process is really the wrong abstraction (computation is reduction, not a sequence of steps performed in temporal order). But what is concurrency if their are no processes to run concurrently? I've beren thinking about action systems and non-determinism, but am unsure how the pieces really fit together. Maybe dataflow languages like Lucid Synchrone, Esterel and Lustre? http://en.wikipedia.org/wiki/Dataflow_language http://en.wikipedia.org/wiki/Synchronous_programming_language For dataflow in Haskell, see Uustalu Vene's comonads paper: http://lambda-the-ultimate.org/node/view/988 I do wish I could find the source code from this paper online, I'd rather not type it in by hand. Do researchers usually manually transcribe code? -- Shae Matijs Erisson - http://www.ScannedInAvian.com/ - Sockmonster once said: You could switch out the unicycles for badgers, and the game would be the same. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Monads in Scala, XSLT, Unix shell pipes was Re: Monads in ...
Maybe this is a different topic, but exploring concurrency in Haskell is definitely on my to do list, but this is really a bit of a puzzle. One thing I've been thinking lately is that in functional programming the process is really the wrong abstraction (computation is reduction, not a sequence of steps performed in temporal order). But what is concurrency if their are no processes to run concurrently? I've beren thinking about action systems and non-determinism, but am unsure how the pieces really fit together. Concurrency in Haskell is handled by forking the execution of IO actions, which are indeed sequences of steps to be performed in a temporal order. There are some elegant constructions in that direction, not least of which is STM, a system for transactional thread communication, on top of which one can implement channels and various other concurrency abstractions. STM allows one to insist that certain restricted kinds of actions relating to thread communication (in the STM monad) occur atomically with respect to other threads. These transactions can create, read and write to a special kind of mutable variable called a TVar (transactional variable). They can also ask to block the thread they are in and be retried later when one of the TVars they observed changes. There is additionally an operator `orElse` where if a and b are STM transactions, then (a `orElse` b) is a transaction where if a is executed and if it retries, then b is attempted, and if it retries, then the whole transaction retries. The first transaction not to retry gets to return its value. The operator `orElse` is associative, and has retry as an identity. The paper describing STM in more detail is here: http://research.microsoft.com/Users/simonpj/papers/stm/index.htm Perhaps more related to what you were thinking about, with Parallel Haskell, there's a mechanism for parallel computation to be used in a similar fashion to seq called par. The expression x `par` (y `seq`(x + y)), when evaluated, will first spark a parallel process for evaluating x (up to the top level data constructor), while in the main task, y `seq` (x + y) is computed, so the evaluation of y proceeds, and the task potentially blocks until x finishes being computed, and then the sum is returned. Sparking x will create the potential for x to be computed in another thread on a separate processor, if one becomes idle, but if that doesn't happen, x will simply be computed on the same processor as y when it is needed for the sum. Hope this is somewhat interesting and perhaps somewhat answers your question :) - Cale ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Dataflow and Comonads was Re: Monads in Scala, ...
Shae Matijs Erisson wrote: I do wish I could find the source code from this paper online, I'd rather not type it in by hand. Do researchers usually manually transcribe code? Both Evince and Acrobat Reader can copy text. Jim ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Dataflow and Comonads was Re: [Haskell-cafe] Monads in Scala, ...
On Sat, 2005-11-26 at 18:43 +0100, Shae Matijs Erisson wrote: Greg Woodhouse [EMAIL PROTECTED] writes: Maybe this is a different topic, but exploring concurrency in Haskell is definitely on my to do list, but this is really a bit of a puzzle. One thing I've been thinking lately is that in functional programming the process is really the wrong abstraction (computation is reduction, not a sequence of steps performed in temporal order). But what is concurrency if their are no processes to run concurrently? I've beren thinking about action systems and non-determinism, but am unsure how the pieces really fit together. Maybe dataflow languages like Lucid Synchrone, Esterel and Lustre? http://en.wikipedia.org/wiki/Dataflow_language http://en.wikipedia.org/wiki/Synchronous_programming_language I also think dataflow is a very nice model for concurrency in pure functional languages. You might want to look at some of the work done by Edward Lee's group in the EE Dept. at Berkeley. They developed a generalization of dataflow called token flow which is quite nice. It became one of the basic models supported by their heterogeneous simulation systems, Ptolemy and Ptolemy II. I seem to recall that one student at a Texas university did a PhD thesis on dataflow for Haskell and then went to work on token flow in Lee's group. The one downside I found to using dataflow was that most software people seem to be uncomfortable with the lack of identifiable processes doing significant bits of work. I guess if they they're not floundering around in mutual exclusion, semaphores, deadlock detection and all the other manifestations of unmanaged complexity, they don't feel they've *accomplished* anything (BTW I grew up on Dijkstra, Hoare and Hanson, so I can get away with saying this :-). Interestingly enough, and perhaps obvious in retrospect, I often found hardware designers to be very comfortable with dataflow computations. Does anyone know whether much research has been done on using dataflow for concurrency in pure functional computation? How does it mesh with evaluation strategies? And, of course, the flip side: has anyone looked at re-examining real-world problems, conventionally handled with coordinating/communicating processes, as dataflow computations? The latter consideration may be the toughest to deal with. I was working on a project to handle PHY level communication algorithms with dataflow, and I had a great deal of difficulty with the comma-detect function of XAUI. I made some progress, but I never found a satisfactory solution. On the other hand, I did work out a fairly nice dataflow algorithm for CRC32. -- Bill Wood ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell GUI on top of Xlib?
Thanks Duncan for this link: a very interesting reading. Duncan Coutts wrote: Are you aware of the XCB library: http://xcb.freedesktop.org/ Indeed they mention that Haskell would be an obvious target for this: http://xcb.freedesktop.org/wiki/XCBToDo I haven't looked at their API closely, but it would not be a problem to generate bindings using HSFFIG unless there are functions taking/returning whole structures, or things like arrays of function pointers which are not yet handled by HSFFIG reliably. It might be worth trying to model their algorithms in Haskell though. They send requests to server semi-lazily (i. e. when request's result is needed, or eventually when the queue is flushed), and retrieve server replies lazily (i. e. on demand). But I am not ready to tell yet, would Haskell's natural laziness be sufficient to implement that, or something involving mutable objects needs to be built on top of the standard I/O stuff. Dimitry Golubovsky Middletown, CT ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Detecting Cycles in Datastructures
On Sat, Nov 19, 2005 at 02:27:06AM +0100, Benjamin Franksen wrote: [You should read some of his papers, for instance the most unreliable techique in the world to compute pi. I was ROTFL when I saw the title and reading it was an eye-opener and fun too.] In addition to being clever and terribly funny, the conclusion foreshadows (inspired?) later work on Enron [1]. Andrew [1] http://www.haskell.org/humor/enron.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
