December 2009 - Haskell-Cafe

Fwd: [Haskell-cafe] Haskell for Physicists
by Don Stewart 05 Dec '09

05 Dec '09

Hey all, Following up on this, I'm presenting a position paper tomorrow on the use of EDSLs to improve productivity and lower cost when developing code for new high performance architectures (like GPUs). http://www.galois.com/blog/2009/10/13/domain-specific-languages-for-domain-… It advocates for Haskell + EDSLs, much as we have been discussing in this thread. -- Don

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inotify-alike for mac os x?
by Conal Elliott 05 Dec '09

05 Dec '09

I'd like to make some FRPish toys that keep files updated to have functional relationships with other files. hinotify looks like just the sort of underlying magic I could use for efficient implementation on linux. Is there any support for mac os x? Could support be either added to hinotify or maybe inotify and a mac-friendly library be abstracted into a common Haskell interface? I'm fine with an imperative interface, since I can abstract into a functional library, which I guess would be a sort of persistent simplified FRP. - Conal

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GHC magic optimization ?
by Emmanuel CHANTREAU 05 Dec '09

05 Dec '09

Hello One thing is magic for me: how GHC can know what function results to remember and what results can be forgotten ? Is it just a stupid buffer algorithm or is there some mathematics truths behind this ? I'm very happy about Haskell, it's so great to put some smart ideas in a computer. thanks -- Emmanuel Chantréau

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Re: Low Level Audio - Writing bytes to the sound card?
by John Lato 05 Dec '09

05 Dec '09

> From: M Xyz <functionallyharmonious(a)yahoo.com> > >> if you get it to work > > As a spoiled Java programmer, this new role as pioneer is a bit intimidating, but I will give it a shot. :) > > I downloaded the portaudio v19 source and I'm attempting to build it. Apparently I have to register my Visual Studio Express with Microsoft. Deeper down the rabbit hole... (Interesting aside, on the registration form under "What programming language topics are you interested in?" neither F# or Haskell are listed) For doing cross-platform development, I would strongly recommend that you use MinGW (or cygwin) in preference to Visual Studio Express. This is because most Unix/Linux packages, and thus most cross-platform packages, are designed to be built with the GNU compiler toolchain (i.e. configure, make, make install), and getting them to work with Visual Studio can be a chore. I also would use PortAudio for what you describe, and have had good experience with it on OSX. Sox is a good choice as well if you don't mind piping output to another program. *shameless plug* you could also use hCsound, although it's probably higher-level than what you're looking for. Installing on Windows is tricky too, but you only need to do so once. John

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Are there major inefficiencies in Haskell compared to OCaml?
by Casey Hawthorne 04 Dec '09

04 Dec '09

Are there major inefficiencies in Haskell compared to OCaml? If so, can something be done about them? -- Regards, Casey

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Greetings! 2D Graphics?
by M Xyz 04 Dec '09

04 Dec '09

Greetings, my name is M. This is my first time posting to a mailing list so forgive me if I've done something wrong. I just finished "Real World Haskell" and am currently working through "School of Expression". I am new to Haskell but I already love it. My question is this... I am interested in doing graphics work in Haskell, but I am lost trying to pick a library. I've been designing engineering apps in Java for 6 years and I'll admit I've been coddled by its standard library, lol. I am looking for something very lightweight with the basic capabilities of Java's Graphics2D class (antialias, composite, clipping, transformation, simple drawing primitives, gradients). I want something simple and "lightweight" because my interest is to play with building higher level abstractions myself. I use XP and Ubuntu so I'd prefer not to use the Graphics-Win32 library used by "School of Expression" if there is a platform independent library. I've read through http://www.haskell.org/haskellwiki/Applications_and_libraries/Graphics and the pertinent libraries seem to be Haven, HGL or Cairo via Gtk2Hs right? Which is the most popular/active and appropriate for a beginner to start working with? Thank you!

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seems like I'm on the wrong track
by Michael P Mossey 04 Dec '09

04 Dec '09

Perhaps someone could either (1) help me do what I'm trying to do, or (2) show me a better way. I have a problem that is very state-ful and I keep thinking of it as OO, which is driving me crazy. Haskell is several times harder to use than Python in this instance, probably because I'm doing it wrong. To give you a larger context, this problem is essentially compiling a description of music (my own) into a kind of music-machine-language (CSound). CSound is relatively untidy. In this one example, in a OO way of thinking, I have data called AssignedNumbers that assigns integers to unique strings and keeps track of the used integers and next available integer (the choice of available integer could follow a number of conventions so I wanted to hide that in an ADT.) So it has an associated function: getNumber :: String -> AssignedNumbers -> (Int,AssignedNumbers) What getNumber does is: - check if the string already has a number assigned to it. If so, return that number. - if not, pick the next available number. - in all cases, return the possibly changed state of AssignedNumbers Then in a larger data structure, it contains fields of type AssignedNumbers. Like data MusicStuff = MusicStuff { oscillatorNumbers :: AssignedNumbers , tableNumbers :: AssignedNumbers , ... } I'm using MusicStuff in a State monad, so I might write a function like doSomeMusicStuff :: String -> String -> State MusicStuff (Int,Int) doSomeMusicStuff aString1 aString2 = do ms <- get (o1,newOscNums) = getNumber aString1 (oscillatorNumbers ms) (t1,newTabNums) = getNumber aString2 (tableNumbers ms) put ms { oscillatorNumbers = newOscNums , tableNumbers = newTabNums } return (o1,t1) For what it does, this is extremely verbose and filled with distracting visual content. And this is just a very simple example---my real problem is several times more state-ful. Is there a better way? Note that in Python it would be a method def doMusicStuff( self, s1, s2 ) : return (self.oscillatorNumbers.next(s1), self.oscillatorNumbers.next(s2))

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Optimization with Strings ?
by John D. Earle 04 Dec '09

04 Dec '09

Dear Emmanuel Chantréau, You may want to look into Objective CAML http://caml.inria.fr/ which is a French product as you can see from the Internet address. It is likely better suited to the task than Haskell and has a reputation for speed. For those who prefer object oriented programming it has facilities for that which may ease your transition from C++. The Microsoft F# language is based on Objective CAML. Haskell has a problem with its type system and is not rigorous. Haskell is not a suitable language for proof assistants and so I would advise you to stay clear of Haskell. Standard ML was engineered with the needs of proof assistants in mind and so you may want to look into Standard ML, but you should be very happy with Objective CAML. It has an excellent reputation. The Coq proof assistant which is another French product is based on Objective CAML. If you do decide that Haskell is the way, it will help ease your transition to Haskell. There is nothing that says you can't keep your fingers in several pies at once.

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FFI and ghci
by Patrick LeBoutillier 04 Dec '09

04 Dec '09

Hi all, I have a small FFI-based library that I like to test like this: $ ghci -I../c -L../c/.libs -lmlp t.hs GHCi, version 6.10.1: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. Loading object (dynamic) mlp ... done final link ... done [1 of 9] Compiling MLP ( MLP.hs, interpreted ) [2 of 9] Compiling MLP.Error ( MLP/Error.hs, interpreted ) [3 of 9] Compiling MLP.Context ( MLP/Context.hs, interpreted ) [4 of 9] Compiling MLP.Runtime ( MLP/Runtime.hs, interpreted ) [5 of 9] Compiling MLP.Object ( MLP/Object.hs, interpreted ) [6 of 9] Compiling MLP.Type ( MLP/Type.hs, interpreted ) [7 of 9] Compiling MLP.Value ( MLP/Value.hs, interpreted ) [8 of 9] Compiling MLP.Language ( MLP/Language.hs, interpreted ) [9 of 9] Compiling Main ( t.hs, interpreted ) Ok, modules loaded: MLP, MLP.Object, Main, MLP.Runtime, MLP.Context, MLP.Error, MLP.Value, MLP.Type, MLP.Language. *Main> main Note: Inside libmlp.so, another shared object is loaded using dlopen(). When running this test program I get some sporadic segmentation faults, which seem to always occur at entrypoint to the shared object that is loaded with dlopen(). But when I compile it with ghc, i.e. $ ghc --make -I../c -L../c/.libs -lmlp t.hs I can't reproduce crash. Can anyone see why this could be happening? It's quite possible that there is really a bug in the C code, but if someone knows about a bug or something in ghci that can cause this behaviour I can stop looking... Thanks a lot, Patrick -- ===================== Patrick LeBoutillier Rosemère, Québec, Canada

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Re: [Haskell-cafe] Is Haskell a Fanatic?
by Brandon S. Allbery KF8NH 04 Dec '09

04 Dec '09

> 2009/12/03 Brandon S. Allbery KF8NH <allbery(a)ece.cmu.edu>: >> This "troll" was, apparently, invited by one of the Simons >> onto the Haskell' list, then asked to move his spiels here. I am informed that the "invitation" I was referring to was actually about his being invited *out*, not in, so his origin is still a mystery and "troll" is likely appropriate. (I can't say he's demonstrated much of a mathematical basis for his trollery; only a propensity for pompous declarations, and deflection when challenged on them. Put up or shut up, troll.) -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery(a)kf8nh.com system administrator [openafs,heimdal,too many hats] allbery(a)ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH

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