September 2008 - Haskell-Cafe

Haskell audio libraries & audio formats
by Eric Kidd 03 Sep '08

03 Sep '08

Greetings, Haskell folks! I'm working on a toy program for drum synthesis. This has lead me to explore the various sound-related libraries in Hackage. Along the way, I've learned several things: 1. There's a lot of Haskell sound libraries, but no agreement on how to represent buffers of audio data. 2. Some of the most useful sound libraries aren't listed in Hackage's "Sound" section, including HCodecs, SDL-mixer and hogg. 3. The Haskell OpenAL bindings are great, but ALUT has been removed from MacOS 10.5. Of course, a pure-Haskell version of ALUT would be pretty easy to write, and it could be used as a fallback. 4. '[[a]]' is _not_ a good representation for multi-channel audio data. Manipulating even 10 seconds of audio is noticeably slow. 5. HCodecs is probably the best library for reading WAVE files. It uses 'DiffUArray Int a' to represent audio data, and not '[[a]]'. It also supports MIDI and SoundFont, which is quite handy. 6. YampaSynth looks really cool, and it might be possible to turn it into a reusable MIDI synthesizer library for use with HCodecs. This would be extremely useful: it would provide a basis for all kinds of crazy MIDI-based programming in Haskell. At the end of this e-mail, you can find a list of Haskell sound libraries and their supported audio formats. What would the ideal Haskell sound API look like? Personally, I would love to see: a. Something like HCodecs's Data.Audio as the basic sound format. Data.Audio is an array-based API, and it supports converting between a wide range of common sample formats. I don't know how fast this is, but it already exists, and it's used by YampaSynth. b. OpenAL for sound playback, with a portable version of ALUT. This may require writing a pure-Haskell version of ALUT. c. Utility functions to convert Data.Audio to OpenAL.AL.Buffer. d. An easy-to-use API for audio processing. It might be possible to start with something like Jack's 'mainMono' and 'mainStereo' functions, which map a function over an audio stream. Other nice-to-have features might include: e. A standard MIDI format, based on either the HCodecs package or the midi package. (HCodecs is used by YampaSynth, and the midi package is used by alsa-midi.) f. A modular version of YampaSynth which can convert MIDI data structures into Data.Audio values. It looks like Haskell could be a really sweet audio programming environment with just a bit of integration work. What do folks think? Are there other libraries I should look at more closely? Other features that should be included in an ideal audio API? Thank you for your advice and feedback! Cheers, Eric Haskell audio libraries Reading and writing sound files: HCodecs: (Audible a) => DiffUArray Int a hsndfile: MArray with Float and Double HSoundFile: [[Double]] ALUT: OpenAL.AL.Buffer WAVE: [[Int32]] Playing sounds: OpenAL: Ptr UInt8, Ptr Int16, 1-N channels SDL-mixer: ForeignPtr ChunkStruct, ForeignPtr MusicStruct Sound processing libraries: dsp: Array a, [a] jack: Operates via mapping functions mainMono :: (CFloat -> IO CFloat) -> IO () mainStereo :: ((CFloat, CFloat) -> IO (CFloat, CFloat)) -> IO () MIDI-based: HCodecs: Reads and writes MIDI files midi: Reads and writes MIDI files alsa-midi: Uses midi library YampaSynth: Stand-alone program Special-purpose APIs only (FFIs, etc.): hCsound: CsoundPtr hsc3: UGen No public sound-buffer API: hbeat: The relevant source files are missing! hogg: Very low-level API for Ogg internals only libmpd: No sound buffer API sonic-visualizer: No sound buffer API truelevel: Stand-alone program (uses WAVE) wavconvert: Stand-alone program

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analyzing modules import/export
by Han Joosten 03 Sep '08

03 Sep '08

I am currently involved with a Haskell project to create a toolset for a formal language. The toolset contains a parser, a typechecker and s range of other features. The Haskell code currently consists of about 20 modules. I am new in the project, and my impression is that a lot of code does not reside in the proper module. I would like to be able to get a good feeling in how the modules are structured, and how they are consumed by other modules. This would enable me to clean up a little bit. I use eclipsefp. Do you know of any way to get insight of the structure of modules? is any tooling available? Any suggestions would help a lot! Thanx for reading. Han Joosten -- View this message in context: http://www.nabble.com/analyzing-modules-import-export-tp19297359p19297359.h… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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joyent, solaris and ghc
by Jason Dusek 03 Sep '08

03 Sep '08

Is anyone on the list using GHC on Joyent's Solaris (x86_64) setup? If so, I would love to know whether it was easy/hard and what the process is. -- _jsn

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Re: [Haskell-cafe] Is it usual to read a Maybe (IORef a) ?
by minh thu 03 Sep '08

03 Sep '08

2008/9/3 Lennart Augustsson <lennart.augustsson(a)gmail.com>: > I think you should think about why your application needs IORef at all. Do > you really need mutation? And why isn't STRef good enough. Using IORef is > really the last resort. This is for an interactive application (3D mesh editing, the data structure is the half edge structure). So the user can add points, edges, faces, delete them, ... Thu

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Types and Trees
by Matt Morrow 03 Sep '08

03 Sep '08

I really learned a lot from writing the below code, and thought I'd share it with the group. I'm slightly at a loss for words, having just spent the last two hours on this when I most certainly should have been doing other work, but these are two hours I won't regret. I'm very interested in hearing others' thoughts on "this", where "this" is "whatever comes to mind". Regards, Matt {-# LANGUAGE MultiParamTypeClasses, FlexibleInstances #-} module TT where import Data.Tree import Data.Typeable (Typeable(..),TypeRep(..),TyCon(..) ,typeRepTyCon,typeRepArgs,tyConString) import Language.Haskell.TH(Type(..),mkName) -------------------------------------------------------- class ToType a where toType :: a -> Type class ToTree a b where toTree :: a -> Tree b {- Typeable a | typeOf | (0) | v toType TypeRep - - - - - - - - > Type | (4) | toTree | (1) (2) | toTree | | v (3) v Tree TyCon ---------------> Tree Type toTree -} -- (0) typeableToTypeRep :: (Typeable a) => a -> TypeRep typeableToTypeRep = typeOf -- (1) instance ToTree TypeRep TyCon where toTree ty = Node (typeRepTyCon ty) (fmap toTree . typeRepArgs $ ty) -- (2) instance ToTree Type Type where toTree (AppT t1 t2) = let (Node x xs) = toTree t1 in Node x (xs ++ [toTree t2]) toTree t = Node t [] -- (3.a) instance ToType TyCon where toType tyC = let tyS = tyConString tyC in case tyS of "->" -> ArrowT "[]" -> ListT "()" -> TupleT 0 ('(':',':rest) -> let n = length (takeWhile (==',') rest) in TupleT (n+2) _ -> ConT . mkName $ tyS -- (3.b) instance ToType (Tree TyCon) where toType (Node x xs) = foldl AppT (toType x) (fmap toType xs) -- (3) instance ToTree (Tree TyCon) Type where toTree = toTree . toType -- (4) instance ToType TypeRep where toType = toType . (toTree::TypeRep->Tree TyCon) -- (0) typeOf -- (1) toTree -- (2) toTree -- (3) toTree -- (4) toType -- (0) -> (1) tyConTree :: (Typeable a) => a -> Tree TyCon tyConTree = toTree . typeOf -- (0) -> (1) -> (3) typeTree_a :: (Typeable a) => a -> Tree Type typeTree_a = (toTree::Tree TyCon->Tree Type) . (toTree::TypeRep->Tree TyCon) . typeOf -- (0) -> (4) -> (2) typeTree_b :: (Typeable a) => a -> Tree Type typeTree_b = (toTree::Type->Tree Type) . (toType::TypeRep->Type) . typeOf diagram_commutes :: (Typeable a) => a -> Bool diagram_commutes a = typeTree_a a == typeTree_b a -- ghci> diagram_commutes x0 -- True x0 :: (Num a) => ((a,(a,((a,a),a))),(a,(a,a))) x0 = ((0,(0,((0,0),0))),(0,(0,0))) -------------------------------------------------------- printTree :: (Show a) => Tree a -> IO () printTree = putStr . drawTree . fmap show printForest :: (Show a) => Forest a -> IO () printForest = putStr . drawForest . (fmap . fmap) show -------------------------------------------------------- {- ghci> printTree $ tyConTree x0 (,) | +- (,) | | | +- Integer | | | `- (,) | | | +- Integer | | | `- (,) | | | +- (,) | | | | | +- Integer | | | | | `- Integer | | | `- Integer | `- (,) | +- Integer | `- (,) | +- Integer | `- Integer ghci> printTree $ typeTree_a x0 TupleT 2 | +- TupleT 2 | | | +- ConT Integer | | | `- TupleT 2 | | | +- ConT Integer | | | `- TupleT 2 | | | +- TupleT 2 | | | | | +- ConT Integer | | | | | `- ConT Integer | | | `- ConT Integer | `- TupleT 2 | +- ConT Integer | `- TupleT 2 | +- ConT Integer | `- ConT Integer ghci> printTree $ typeTree_b x0 TupleT 2 | +- TupleT 2 | | | +- ConT Integer | | | `- TupleT 2 | | | +- ConT Integer | | | `- TupleT 2 | | | +- TupleT 2 | | | | | +- ConT Integer | | | | | `- ConT Integer | | | `- ConT Integer | `- TupleT 2 | +- ConT Integer | `- TupleT 2 | +- ConT Integer | `- ConT Integer -} --------------------------------------------------------

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What monad am I in?
by Henry Laxen 03 Sep '08

03 Sep '08

Dear Group, When I fire up ghci and define: increment x = return (x+1) I can say: Main> increment 1 and ghci dutifully replies 2. Also as expected, the type signature of increment is: (Num a, Monad m) => a -> m a However, if I say: Main> let a = increment 1 I get: <interactive>:1:8: Ambiguous type variable `m' in the constraint: `Monad m' arising from a use of `increment' at <interactive>:1:8-18 Probable fix: add a type signature that fixes these type variable(s) Have I, like Monsier Jourdain, been running in the IO monad all my life, and didn't even know it? Thanks, Henry Laxen

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ANN: zip-archive 0.0
by John MacFarlane 03 Sep '08

03 Sep '08

I've written a library, zip-archive, for dealing with zip archives. Haddock documentation (with links to source code): http://johnmacfarlane.net/zip-archive/ Darcs repository: http://johnmacfarlane.net/repos/zip-archive/ It comes with an example program that duplicates some of the functionality of 'zip' (configure with '-fexecutable' to build it). I intend to put it on HackageDB, but I thought I'd get some feedback first. Bug reports, patches, and suggestions on the API are all welcome. John

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Arrow without `>>>'
by Valery V. Vorotyntsev 03 Sep '08

03 Sep '08

Hi, friends, I've built GHC from darcs, and... Could anybody tell me, what's the purpose of Arrow[1] not having `>>>' method? 1. http://darcs.haskell.org/packages/base/Control/Arrow.hs $ ghci GHCi, version 6.9.20080104: http://www.haskell.org/ghc/ :? for help Loading package base ... linking ... done. Prelude> :m + Control.Arrow Prelude Control.Arrow> :i Arrow class (Control.Category.Category a) => Arrow a where arr :: (b -> c) -> a b c pure :: (b -> c) -> a b c first :: a b c -> a (b, d) (c, d) second :: a b c -> a (d, b) (d, c) (***) :: a b c -> a b' c' -> a (b, b') (c, c') (&&&) :: a b c -> a b c' -> a b (c, c') -- Defined in Control.Arrow instance Arrow (->) -- Defined in Control.Arrow instance (Monad m) => Arrow (Kleisli m) -- Defined in Control.Arrow Prelude Control.Arrow> Leaving GHCi. I can't build[2] arrows-0.3 package without `>>>' in Arrow. 2. vvv@fun:~/src/arrows$ darcs w { hunk ./Control/Arrow/Operations.hs 36 +import Control.Category ((>>>)) hunk ./Control/Arrow/Transformer/CoState.hs 23 +import Control.Category ((>>>)) } vvv@fun:~/src/arrows$ runhaskell Setup build Preprocessing library arrows-0.3... Building arrows-0.3... [ 3 of 12] Compiling Control.Arrow.Transformer.CoState ( Control/Arrow/Transformer/CoState.hs, dist/build/Control/Arrow/Transformer/CoState.o ) Control/Arrow/Transformer/CoState.hs:29:7: `>>>' is not a (visible) method of class `Arrow' The question arises "should I?", but this is one of lambdabot's[3] depencies. 3. http://code.haskell.org/lambdabot/ Thanks a lot! -- vvv

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ICFP09 Announcement
by Matthew Fluet (ICFP Publicity Chair) 02 Sep '08

02 Sep '08

+--------------------------------------------------------------------+ ANNOUNCEMENT The 14th ACM SIGPLAN International Conference on Functional Programming ICFP 2009 31st August - 2nd September 2009 Edinburgh, United Kingdom ICFP provides a forum for researchers and developers to hear about the latest work on the design, implementations, principles, and uses of functional programming. ICFP 2009 will be held in Scotland's historic capital city of Edinburgh, during the final week of the Edinburgh International Festival. Further information is available from: http://www.cs.nott.ac.uk/~gmh/icfp09.html Graham Hutton General Chair, ICFP 2009 +--------------------------------------------------------------------+ | Dr Graham Hutton Email : gmh(a)cs.nott.ac.uk | | Functional Programming Lab | | School of Computer Science Web : www.cs.nott.ac.uk/~gmh | | University of Nottingham | | Jubilee Campus, Wollaton Road Phone : +44 (0)115 951 4220 | | Nottingham NG8 1BB, UK | +--------------------------------------------------------------------+

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REMINDER: OpenSPARC project application deadline this Friday
by Duncan Coutts 02 Sep '08

02 Sep '08

http://haskell.org/opensparc/ The deadline for applications for the Haskell OpenSPARC project is rapidly approaching. Applications have to be sent to: opensparc(a)community.haskell.org by the end of this week, Friday the 5th September. If you want any comments on your application before you submit it then contact me directly. Duncan (project coordinator) In other news, the server that Sun Microsystems donated to the community has just gone online at Chalmers: http://blog.well-typed.com/2008/09/the-new-haskellorg-community-sparc-serve…

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