November 2005 - Haskell-Cafe

RE: [Haskell-cafe] Detecting Cycles in Datastructures
by Simon Peyton-Jones 01 Dec '05

01 Dec '05

| Andrew Pimlott: | //about my highly spiritual essay on lazy computing of PI//: | | > In addition to being clever and terribly funny, the conclusion | > foreshadows (inspired?) later work on Enron [1]. | | Come on, it is improbable that Master Simon ever read my essay... I hadn't before, but I have now. Cool stuff. I once wrote a continued-fraction package with the something of the same flavour (since overtaken by David Lester's work, which to my deep sadness remains unpublished to this day). Your code clearly belongs in the nofib suite, as a splendid way to consume compute cycles and test compilers. Do send me a Main.hs to compute pi, with a changeable runtime (presumably just adjust 'take'). Simon

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Oops, Hsc license is clearly GPL in the Hsc.cabal file was Re: Hacking Haskell in Nightclubs?
by rd＠slavepianos.org 30 Nov '05

30 Nov '05

> My mistake, the Hsc.cabal file clearly states GPL. (I assume I can choose > either GPL v1 or v2 ?) The SuperCollider server is GPL v2. As this is just an interface to the server, I think it should have the same license. I haven't worked out about the Cabal yet, but it's on my todo list, and then I'll make the version number explicit. Rohan

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Hacking Haskell in Nightclubs?
by rd＠slavepianos.org 30 Nov '05

30 Nov '05

Real-time audio is much simpler these days due to SuperCollider, a truly excellent cross platform audio synthesis server by James McCartney. http://www.audiosynth.com http://supercollider.sf.net To communicate with the server one only needs to implement the most basic aspects of the Open Sound Control (OSC) byte protocol (in particular none of the pattern matching is required). http://www.opensoundcontrol.org/ To define 'instruments' there is a SuperCollider specific byte protocol for describing Unit Generator (UGen) graphs. I have an initial Haskell implementation of both these protocols at: http://www.slavepianos.org/rd/f/207949/ darcs get http://www.slavepianos.org/rd/sw/sw-69/ If SuperCollider is running on the local host at the usual port then: Hsc*> play' sc ab Hsc*> stop' sc should play (and then stop playing) the famous 'Analog Bubbles' test sound: ab = out AR 0 $ combn AR s 0.2 0.2 4 where s = sinosc AR (midicps f) 0 * 0.1 f = lfsaw KR 0.4 0 * 24 + o o = lfsaw KR (MCE [8, 7.23]) 0 * 3 + 80 The Hsc module can also write UGen graphs to the 'dot' language, so graphs can be drawn automatically, which can be useful for debugging. I have been working with scheme and SuperCollider for some time, but have been using haskell recently and generally like it very well. I don't think static typing is an issue. OSC messages can be timestamped, and SuperCollider has a sample accurate scheduling queue, so language timing jitter can easily be worked around. I think that the SuperCollider model is an excellent fit with languages like Haskell. Regards, Rohan On Mon Nov 28 21:35:38 EST 2005 Paul Hudak wrote: > Although Haskore (haskell.org/haskore) doesn't currently support > real-time music, it's something I've thought about numerous times in the > past, and wish I had the time to do it... > > -Paul Hudak > > > Echo Nolan wrote: > > Hello all, > > I read an article on using perl for live improvised synthesis a > > while ago (http://www.perl.com/pub/a/2004/08/31/livecode.html) Does > > anyone have thoughts in doing this is haskell? Would strong typing make > > "jazzy" programming too difficult?

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type inference algorithm for type classes
by robert wong 30 Nov '05

30 Nov '05

Hi All, I have been developing a type inference system which is very similar to type classes' (by Wadler and Blott). However, I cannot find a detailed description of the algorithm. In "Type Classes in Haskell", implementation issues are discussed briefly. However, it is too brief for me to grasp. Does anybody have any suggestion on where to look? Thanks, Robert _________________________________________________________________ Get an advanced look at the new version of MSN Messenger. http://messenger.msn.com.sg/Beta/Default.aspx

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RE: [Haskell-cafe] STM, orElse and timed read from a channel
by Simon Marlow 29 Nov '05

29 Nov '05

On 29 November 2005 12:47, Joel Reymont wrote: > Where is this "registerTimeout" in the GHC code? Well, it's not there yet :-) But I've hacked up an implementation this morning so it might be in GHC 6.6. Cheers, Simon

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R: [Haskell-cafe] Hacking Haskell in Nightclubs?
by Santoemma Enrico 29 Nov '05

29 Nov '05

Doing music is a hard low level problem, a concurrency problem and is also an interesting problem for intelligent and behavioural computation. If it's true that Haskell can do its best on the second and third aspect, the undertaking seems to wrap with foreing interface one of the many good C libraries for low level audio/midi management. Btw, about the third aspect I liked your approach to model animations through behaviour in your book School of expressions. So now the questions seem to be: how difficult is today to wrap a C library? Which is the right tool to do it? C->Haskell? Salus, Enrico > -----Messaggio originale----- > Da: haskell-cafe-bounces(a)haskell.org > [mailto:haskell-cafe-bounces@haskell.org]Per conto di Paul Hudak > Inviato: martedì 29 novembre 2005 3.36 > A: Echo Nolan > Cc: haskell-cafe(a)haskell.org; paul.hudak(a)yale.edu > Oggetto: Re: [Haskell-cafe] Hacking Haskell in Nightclubs? > > > Although Haskore (haskell.org/haskore) doesn't currently support > real-time music, it's something I've thought about numerous > times in the > past, and wish I had the time to do it... > > -Paul Hudak > > > Echo Nolan wrote: > > Hello all, > > I read an article on using perl for live improvised synthesis a > > while ago (http://www.perl.com/pub/a/2004/08/31/livecode.html) Does > > anyone have thoughts in doing this is haskell? Would strong > typing make > > "jazzy" programming too difficult? > > Regards, > > Echo Nolan > > -- > Professor Paul Hudak > Department of Computer Science Office: (203) 432-1235 > Yale University FAX: (203) 432-0593 > P.O. Box 208285 email: paul.hudak(a)yale.edu > New Haven, CT 06520-8285 WWW: www.cs.yale.edu/~hudak > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >

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RE: [Haskell-cafe] STM, orElse and timed read from a channel
by Simon Marlow 29 Nov '05

29 Nov '05

On 29 November 2005 06:29, Tomasz Zielonka wrote: > On Mon, Nov 28, 2005 at 11:27:46PM +0000, Joel Reymont wrote: >> Folks, >> >> How would you implement a timed read from a channel with STM? I would >> like to return Timeout if nothing was read from a TChan in X ms. >> >> Is this a basic two-thread timeout implementation or is there a more >> elegant way of implementing this using `orElse`? > > Here is a basic two-thread implementation: > > http://www.haskell.org/pipermail/haskell-cafe/2005-January/008303.html > > The other approach I see is to create a TVar that would be updated > with current time every 0.1 s (or something like that), but that would > be rather inefficient. > > You could also create a time-out manager thread (with a priority > queue, etc), so you don't have to spawn a thread for every timeout. Interestingly, GHC already has a timeout thread - the I/O manager thread handles threadDelay too. It wouldn't be too hard to adapt it to do STM timeouts too, with a function like registerTimeout :: Int -> STM (TVar Bool) and you wait for your timeout by waiting for the TVar to contain True. Cheers, Simon

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STM, orElse and timed read from a channel
by Joel Reymont 29 Nov '05

29 Nov '05

Folks, How would you implement a timed read from a channel with STM? I would like to return Timeout if nothing was read from a TChan in X ms. Is this a basic two-thread timeout implementation or is there a more elegant way of implementing this using `orElse`? Thanks, Joel -- http://wagerlabs.com/

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Hacking Haskell in Nightclubs?
by Echo Nolan 28 Nov '05

28 Nov '05

Hello all, I read an article on using perl for live improvised synthesis a while ago (http://www.perl.com/pub/a/2004/08/31/livecode.html) Does anyone have thoughts in doing this is haskell? Would strong typing make "jazzy" programming too difficult? Regards, Echo Nolan

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Lazier I/O?
by Dimitry Golubovsky 28 Nov '05

28 Nov '05

This may be a stupud question, but how to make I/O in Haskell really lazy? Here is a simple program: ==== module Main where import System.IO import Foreign import Data.Word import Data.Char s2c :: String -> [Word8] s2c s = map (fromIntegral . ord) s sendstr :: Handle -> String -> IO Int sendstr h s = do let c = s2c s ln = length c allocaBytes ln $ \buf -> do pokeArray buf c hPutBuf h buf ln return ln main = do hSetBuffering stdout NoBuffering l1 <- sendstr stdout "abcde\n" l2 <- sendstr stdout "defghij\n" putStrLn $ "sent " ++ (show l2) ++ " bytes" putStrLn $ "sent " ++ (show l1) ++ " bytes" ==== It prints: abcde defghij sent 8 bytes sent 6 bytes i. e. the first string is output first although the result from that output (how many bytes sent) is needed second. What is desired is to have the IO actions perform as their results are needed. I am assuming some knowledge that those actions have only limited scope of side effects (e. g. order of outputs within a window is significant, but order of appearance of those windows on the screen may not be). I see some way to do this by writing regular non-monadic Haskell stuff, representing each side effects scope (i. e. where ordering of actions is necessary) with its own instance of an I/O like monad (but runnable from an outside non-monadic code), and then using unsafePerformIO as needed. But there may be some framework already developed (albeit with unsafePerformIO, but hiding it from application developers). Any ideas, pointers? Thanks Dimitry

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