Re: [Haskell-cafe] Re: HFuse: ls fails in HelloFS
On Mar 19, 2008, at 2:12 , Austin Seipp wrote: Excerpts from Will Thompson's message of Sun Mar 16 08:37:00 -0500 2008: Currently the module's name is HFuse. Presumably it really belongs under System somewhere; System.Posix.Fuse maybe? What do folks think? Are there any guidelines for picking a namespace? I don't think there's any sort of doc on picking a namespace or how to logically name your package modules (would likely be worth writing); for something like this, I would say something under System.Posix.* would be the most appropriate. Erm, POSIX does not mean Linux and sufficiently similar systems. FUSE is supported by open source Unixlikes, not by POSIX compliant systems in general. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] [EMAIL PROTECTED] system administrator [openafs,heimdal,too many hats] [EMAIL PROTECTED] electrical and computer engineering, carnegie mellon universityKF8NH ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: HFuse: ls fails in HelloFS
mad.one: Excerpts from Will Thompson's message of Sun Mar 16 08:37:00 -0500 2008: Currently the module's name is HFuse. Presumably it really belongs under System somewhere; System.Posix.Fuse maybe? What do folks think? Are there any guidelines for picking a namespace? I don't think there's any sort of doc on picking a namespace or how to logically name your package modules (would likely be worth writing); for something like this, I would say something under System.Posix.* would be the most appropriate. Ah, but there is! http://haskell.org/haskellwiki/Hierarchical_module_names Enjoy! -- Don (grumbler of packages that use uncommon top level names) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Any ideas for - (function type) in a simply-typed lambda calculus version of Brett Victor's Alligator Eggs game?
Brett Victor has invented an Alligator Eggs game (very loosely resembling Conway's Game of Life), using formal rules to determine feeding and breeding patterns for alligators and their eggs, but the game represents the *untyped* lambda calculus: Alligator Eggs! http://worrydream.com/AlligatorEggs/ I am interested in adapting this to the *simply typed* lambda calculus with Curry-style typing, to aid students of Haskell. Brett Victor's game currently aids students of LISP, and I think that it would be helpful to have a Haskell counterpart (see http://wadler.blogspot.com/2007/05/oh-no-alligators.html for a comment on how the Alligator Eggs game has been used by EE students at Caltech in learning LISP): Simply typed lambda calculus - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Simply_typed_lambda_calculus Thereafter, I would like to create a new entry for this Haskell version of Alligator Eggs on HaskellWiki, and create a link to it under a new subsection, Board Games, under the current Learning Haskell category: http://www.haskell.org/haskellwiki/Learning_Haskell In Brett Victor's version, the following representations hold: * a hungry alligator: lambda abstraction * an old alligator: a pair of parentheses * an egg: a variable * the Eating Rule: beta-reduction * the Color Rule: (over-cautious) alpha-conversion * the Old Age Rule: the rule that a pair of parentheses containing a single term may be removed However, in thinking about how to adapt the game, I am not quite sure how to incorporate the representation of - (function type): * ???: - (function type) What ideas, if any, would anybody have on how - (function type) could be represented in a simply-typed lambda calculus version of Brett Victor's Alligator Eggs? Benjamin L. Russell ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: GADT rhymes with cat
[EMAIL PROTECTED] wrote in article [EMAIL PROTECTED] in gmane.comp.lang.haskell.cafe: Quoting Jeremy Apthorp [EMAIL PROTECTED]: Clearly, this pronounciation is gay dee tea. I always new those types were a bit queer. Not that there's anything wrong with that. ... If it type-checks, it must be correct! I thought the t was silent as well, an unaspirated stop? Egad! -- Edit this signature at http://www.digitas.harvard.edu/cgi-bin/ken/sig Is mathematics a syntax of language? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Scoping in template haskell
Hi all, I am trying to get familiar with template haskell and I'm wondering whether the following is possible and if so, how it would be done properly... I have two templates, and I'd like to use one from the other. For instance the first one might be gen1 :: Int - ExpQ gen1 i = [| ++ (show i) ++ |] Thus, I gould do $(gen1 42) and I'd get 42 now I'd like to use gen2 in another generated expression so that I could so $(gen2 [42, 66]) and get 4266 My naive intention was to write gen2 :: [Int] - ExpQ gen2 is = [| map (\x - $(gen1 x)) is |] which gives me Stage error: `x' is bound at stage 2 but used at stage 1 So I guess my actual question would be: how do I pass a variable bound outside a quotation into another splice used in that quotation? Bests, Lars ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Dynamic typing makes you more productive?
On Tue, Mar 18, 2008 at 09:41:15AM -0700, Justin Bailey wrote: Two years ago I would have agreed with that statement. Now - no way. Make the compiler work for you. I've done a lot of Ruby development and I would never use it for a project of more than 3 or 4 people. It's an awesome language but I don't think it would scale to programming in the large. Any object can be modified at any time. Determining where a particular method comes from can be an exercise in Sherlockian deduction. Give an organization of 100 developers that much freedom and I can only imagine chaos would result. It looks from the outside like Ruby is going through some growing pains as a result of the excerise of too much freedom at the moment. But I wouldn't write Ruby off on account of that: an interesting article I read recently made the comparision with Emacs lisp which offers a similar level of power to the programmer, in that pretty much any function can be redefined at any point, and yet it has a thriving culture of Emacs extensions, all written by disparate people who manage not to step on each other's toes. IOW, it's a cultural issue as well as a language issue. Ruby programmers will no doubt develop their own culture of what is and isn't allowed in publically available extensions just as Emacs lisp programmers have. Phil -- http://www.kantaka.co.uk/ .oOo. public key: http://www.kantaka.co.uk/gpg.txt ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Satnam Singh of Microsoft Research
Hello, I contacted Satnam Singh about this talk and we tried to arrange with Stanford to video record the presentation, but it was not possible on the short notice... __ Donnie On 3/18/08, Galchin Vasili [EMAIL PROTECTED] wrote: oops ... my bad ... it was at Standford's CS dept on Feb 29 at 1:30: This presentation describes a variety of ways to write parallel and concurrent programs in the lazy functional language Haskell. We start off by introducing par/pseq annotations which provide guidance to the run-time about how work can be performed speculatively which provides a basic mechanism for writing implicitly parallel programs. We then describe how a library of strategies can be used to force specific evaluation orders which are necessary to exploit parallelism. We then go on to describe the basic mechanism for writing explicitly parallel programs using Haskell's lightweight threads and then we describe how Haskell's STM implementation can help to write programs that share state between threads through the use of a special monads and as an example we describe the implementation of a multi-way rendezvous library. We then describe some work with Tim Harris on feedback directed implicit parallelism which provides yet another way to write implicitly parallel programs with out resorting to par/pseq annotations. Finally, we report on the progress of a nested data parallel library for Haskell inspired by the NESL language. Throughout the talk we shall emphasizes how Haskell's pure nature (with side effecting operations clearly indicated by the type system) facilitates the exploitation of parallelism. It would be great to get more than the above! Regards. Vasili On 3/18/08, Adam Langley [EMAIL PROTECTED] wrote: 2008/3/18 Galchin Vasili [EMAIL PROTECTED]: Recently Satnam Singh of Microsoft Research gave a talk at Google about concurrency, Haskell STM, etc. Was there a transcript of this talk? Do you have the exact date of this talk? I can't see that anyone called Satnam has given a talk at Google. (It might have been very informal, in which case there wouldn't be a record of it, and nor would there be a video) Cheers, AGL -- Adam Langley [EMAIL PROTECTED] http://www.imperialviolet.org ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Satnam Singh of Microsoft Research
Related news -- Intel, Microsoft choose UC-Berkeley to host $10M parallel computing center March 19, 2008 8:36 AM ET http://news.moneycentral.msn.com/provider/providerarticle.aspx?feed=ACBJdate=20080319id=8361298 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Equality constraints in type families
type family F a :: * - *
..
We made the design
choice that type functions with a higher-kinded result type must be
injective with respect to the additional paramters. I.e. in your case:
F x y ~ F u v = F x ~ F u /\ y ~ v
i'm still trying to understand this remark:
- if we are talking about type functions, i should be allowed
to replace a function application with its result, and if that
result doesn't mention some parameters, they shouldn't
play a role at any stage, right?
- if anything other than the function result matters, isn't it
somewhat misleading to speak of type functions?
- if the parameters have to match irrespective of whether
they appear in the result, that sounds like phantom types.
ok, but we're talking about a system that mixes unification
with rewriting, so shouldn't the phantom parameters be
represented in all rewrite results, just to make sure they
cannot be ignored in any contexts?
ie, with
type instance F a = rhs
F a x should rewrite not to rhs, but to rhs_x,
which would take care of the injectivity you want in the
~-case, but would also preserve the distinction if
rewriting should come before ~, even if rhs managed
to consume x, by being a constant function on types.
- things seem to be going wrong in the current implementation.
consider this code, accepted by GHCi, version 6.9.20080317:
--
{-# LANGUAGE TypeFamilies #-}
type family Const a :: * - *
type instance Const a = C a
type C a t = a
f :: Const Bool Int - Const Bool Char - Const Bool Bool
f i c = False
-- f i c = i
f i c = i True
f i c = (i || c)
--
(note the partially applied type synonym in the type instance,
which is a constant function on types). it looks as if:
- False::Bool is accepted as Const Bool Bool
- i::Const Bool Int is accepted as Bool
- c::Const Bool Char is accepted as Bool
- both i and c are accepted as Bool, so seem to be of
an equivalent type, but aren't really..
- i::Const Bool Int is not accepted as Const Bool Char
directly, but is accepted via one of the eta expansions
for Bool, namely (True)
my current guess is that the implementation is incomplete,
but that the idea of type functions also needs to be adjusted
to take your design decision into account, with phantom types
and type parameter annotations for type function results
suggesting themselves as potentially helpful concepts?
or, perhaps, the implication isn't quite correct, and
type parameters shouldn't be unified unless they appear
in the result of applying the type function? the implementation
would still be incomplete, but instead of rejecting more of the
code, it should allow the commented-out case as well?
could you please help me to clear up this confusion?-)
thanks,
claus
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Re: [Haskell-cafe] Equality constraints in type families
could you please help me to clear up this confusion?-) Let me summarize :-) The current design for type functions with result kinds other than * (e.g. * - *) has not gotten very far yet. We are currently stabilizing the ordinary * type functions, and writing the story up. When that's done we can properly focus on this issue and consider different design choices. Cheers, Tom -- Tom Schrijvers Department of Computer Science K.U. Leuven Celestijnenlaan 200A B-3001 Heverlee Belgium tel: +32 16 327544 e-mail: [EMAIL PROTECTED] url: http://www.cs.kuleuven.be/~toms/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Equality constraints in type families
type family F a :: * - *
..
We made the design
choice that type functions with a higher-kinded result type must be
injective with respect to the additional paramters. I.e. in your case:
F x y ~ F u v = F x ~ F u /\ y ~ v
actually, i don't even understand the first part of that:-(
why would F x and F u have to be the same functions?
shouldn't it be sufficient for them to have the same result,
when applied to y and v, respectively?
consider:
--
type family G1 a :: * - *
type instance G1 a = G3
type family G2 a :: * - *
type instance G2 a = G4
type family G3 a :: *
type instance G3 Bool = Bool
type instance G3 Char = Bool
type family G4 a :: *
type instance G4 Bool = Char
type instance G4 Char = Bool
h :: G1 a Bool ~ G2 a Char = G1 a Bool
h = True
--
for which GHCi, version 6.9.20080317 happily infers
*Main :t h
h :: G1 a Bool
*Main h
True
even though G1 a ~ G3 ~/~ G4 ~ G2 a ?
claus
i'm still trying to understand this remark:
- if we are talking about type functions, i should be allowed
to replace a function application with its result, and if that
result doesn't mention some parameters, they shouldn't
play a role at any stage, right?
- if anything other than the function result matters, isn't it
somewhat misleading to speak of type functions?
- if the parameters have to match irrespective of whether
they appear in the result, that sounds like phantom types.
ok, but we're talking about a system that mixes unification
with rewriting, so shouldn't the phantom parameters be
represented in all rewrite results, just to make sure they
cannot be ignored in any contexts?
ie, with
type instance F a = rhs
F a x should rewrite not to rhs, but to rhs_x,
which would take care of the injectivity you want in the
~-case, but would also preserve the distinction if
rewriting should come before ~, even if rhs managed
to consume x, by being a constant function on types.
- things seem to be going wrong in the current implementation.
consider this code, accepted by GHCi, version 6.9.20080317:
--
{-# LANGUAGE TypeFamilies #-}
type family Const a :: * - *
type instance Const a = C a
type C a t = a
f :: Const Bool Int - Const Bool Char - Const Bool Bool
f i c = False
-- f i c = i
f i c = i True
f i c = (i || c)
--
(note the partially applied type synonym in the type instance,
which is a constant function on types). it looks as if:
- False::Bool is accepted as Const Bool Bool
- i::Const Bool Int is accepted as Bool
- c::Const Bool Char is accepted as Bool
- both i and c are accepted as Bool, so seem to be of
an equivalent type, but aren't really..
- i::Const Bool Int is not accepted as Const Bool Char
directly, but is accepted via one of the eta expansions
for Bool, namely (True)
my current guess is that the implementation is incomplete,
but that the idea of type functions also needs to be adjusted
to take your design decision into account, with phantom types
and type parameter annotations for type function results
suggesting themselves as potentially helpful concepts?
or, perhaps, the implication isn't quite correct, and
type parameters shouldn't be unified unless they appear
in the result of applying the type function? the implementation
would still be incomplete, but instead of rejecting more of the
code, it should allow the commented-out case as well?
could you please help me to clear up this confusion?-)
thanks,
claus
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[Haskell-cafe] ghc 6.8.2 and timer_create error
I have a gentoo box with ghc 6.8.2, and the binaries that ghc builds on that box do not work on redhat EL 4 or ubuntu 7.10. When I try to run the binary, i get an error: Main: timer_create: Invalid argument so is there any way to get ghc to build a binary that doesn't use timer_create? or is that something that is configured when ghc itself is built, if so, how do I turn that feature off? Thanks ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Scoping in template haskell
First off, the first code isn't doing exactly what you think; gen1 3, for example, generates the parse tree: ++ show 3 ++ You can improve this in the following way: gen1 i = let x = ++ show i ++ in [| x |] which generates (for gen1 3, again) ['', '', '3', '', ''] Alternatively, you can generate the expression directly: gen1 i = LitE $ StringE $ ++ show i ++ which gives you exactly the parse tree 3. Now, the compiler will definitely treat the last two the same, but I'm not sure it will constant-fold show 3 into 3 in your case. The runQ trick is really useful; in ghci; just use runQ with the code that you want to generate: :set -fth :m +Language.Haskell.TH runQ [| 4266 |] LitE (StringL 4266) You then just need to figure out how to make that object from the inputs you have. Also, here's something simple to try: appendStrQ :: [ExpQ] - ExpQ appendStrQ = foldr (\x rest - [| $(x) ++ $(rest) |]) [| |] gen2 = appendStrQ . map gen1 -- ryan On Wed, Mar 19, 2008 at 5:17 AM, Lars Oppermann [EMAIL PROTECTED] wrote: Hi all, I am trying to get familiar with template haskell and I'm wondering whether the following is possible and if so, how it would be done properly... I have two templates, and I'd like to use one from the other. For instance the first one might be gen1 :: Int - ExpQ gen1 i = [| ++ (show i) ++ |] Thus, I gould do $(gen1 42) and I'd get 42 now I'd like to use gen2 in another generated expression so that I could so $(gen2 [42, 66]) and get 4266 My naive intention was to write gen2 :: [Int] - ExpQ gen2 is = [| map (\x - $(gen1 x)) is |] which gives me Stage error: `x' is bound at stage 2 but used at stage 1 So I guess my actual question would be: how do I pass a variable bound outside a quotation into another splice used in that quotation? Bests, Lars ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Scoping in template haskell
On Wed, Mar 19, 2008 at 10:46 AM, Ryan Ingram [EMAIL PROTECTED] wrote: gen1 i = LitE $ StringE $ ++ show i ++ Oops, two mistakes here: 1) StringE should be StringL 2) splices need to be in the Q monad. To fix (2), you can either add a return here, or, there are conveniently lowercase constructors for much of TH that return results in the Q monad: gen1 i = return $ LitE $ StringL $ ++ show i ++ or gen1 i = litE $ StringL $ ++ show i ++ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: ghc 6.8.2 and timer_create error
This was discussed in http://www.haskell.org/pipermail/glasgow-haskell-users/2008-March/014498.html Your final guess is correct. #undef HAVE_TIMER_CREATE and/or USE_TIMER_CREATE in mk/config.h HTH Christian Anatoly Yakovenko wrote: I have a gentoo box with ghc 6.8.2, and the binaries that ghc builds on that box do not work on redhat EL 4 or ubuntu 7.10. When I try to run the binary, i get an error: Main: timer_create: Invalid argument so is there any way to get ghc to build a binary that doesn't use timer_create? or is that something that is configured when ghc itself is built, if so, how do I turn that feature off? Thanks ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Using HaskellDb to connect to PostgresSql
Hello, I'm trying to learn to use HaskellDb. I have managed to finally compile and install it on my linux box (I have ghc 6.8.2). But when I try to create a database description (as described in http://haskelldb.sourceforge.net/getting-started.html) (using DBDirect-dynamic instead of DBDirect) I'm stuck. I have tried different names for the driver but I always get the message 'DBDirect-dynamic: user error (Missing field driver)'. Has someone get this working for PostgresSQL and if so, can he/she help me out with some instructions. Also if someone has some pointers to more recent documentation of HaskellDB, I would really be pleased if I could get these. Marc Mertens ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] libmad and os/x coreaudio wrappers
Hi there! I've taken my first stab at writing some (admittedly minimal) libraries for Haskell, and would love to get feedback on them: * hmad: a wrapper for the libmad MP3 decoder. http://maubi.net/~waterson/REPO/hmad * CoreAudio: a wrapper for OS/X CoreAudio. http://maubi.net/~waterson/REPO/CoreAudio (You should be able to darcs get the above links, if you want.) I wrote the libmad wrapper to generate a stream (i.e., a lazy list) of audio samples. CoreAudio allows the input stream to be lazy, as well. So, here's a simple MP3 player: module Main where import Sound.CoreAudio import Codec.Audio.MP3.Mad import qualified Data.ByteString.Lazy as B import System import System.IO main :: IO () main = do files - getArgs mapM_ playFile files playFile :: String - IO () playFile file = withBinaryFile file ReadMode $ \ inHandle - do xs - B.hGetContents inHandle samples - decode xs play samples I do have a couple questions... * The CoreAudio library requires its users to be compiled with -threaded. Is there a way to specify that in the Cabal file? * I wanted to be able to generate a variety of streams from libmad. Besides stereo linear PCM data, it also seemed like it might be worth-while to produce a stream of MP3 frame headers, the unsynthesized frequency domain data, and so on. I tried to accomplish this with a the DecoderSink class, but I'm not sure I succeeded. Any thoughts here would be appreciated! I hope someone else finds these useful. The FFI was a joy to use once I figured it out... :) chris ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Equality constraints in type families
Let me summarize :-) The current design for type functions with result kinds other than * (e.g. * - *) has not gotten very far yet. We are currently stabilizing the ordinary * type functions, and writing the story up. When that's done we can properly focus on this issue and consider different design choices. thanks, seems i was too optimistic, then!-) btw, i noticed that the user guide points to the haskell wiki only, while the latest info seems to be on the ghc wiki. given the number of variations and the scope of development, it would also be helpful if the user guide had at least a one-paragraph executive summary of the state of play, dated to clarify how up-to-date that summary is. that would avoid discussions of not yet stabilized features (should ghc issue a warning when such are used?). claus ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Using HaskellDb to connect to PostgresSql
On Wed, Mar 19, 2008 at 10:55 AM, Marc Mertens [EMAIL PROTECTED] wrote: Hello, I'm trying to learn to use HaskellDb. I have managed to finally compile and install it on my linux box (I have ghc 6.8.2). But when I try to create a database description (as described in http://haskelldb.sourceforge.net/getting-started.html) (using DBDirect-dynamic instead of DBDirect) I'm stuck. I have tried different names for the driver but I don't have much information about using DBDynamic, but I am able to connect to PostgreSQL easily. I have done it on Windows using GHC 6.8.2. I am using hdbc-postgresql, since hsql would not compile on Windows for me. Here are the import statements and the login function I have for a simple program that connects to postgresql and writes out table info: import Database.HaskellDB.DBSpec.DatabaseToDBSpec import Database.HaskellDB.DBSpec.DBSpecToDBDirect import Database.HaskellDB.Database import Database.HaskellDB.HDBC.PostgreSQL import Database.HaskellDB.PrimQuery import Database.HaskellDB.FieldType import Database.HaskellDB.DBSpec login :: MonadIO m = String - Int - String - String - String - (Database - m a) - m a login server port user password dbname = postgresqlConnect [(host, server), (port, show port), (user, user), (password, password), (dbname, dbname)] The versions of all packages I'm using are: HDBC-1.1.4 HDBC-postgresql-1.1.4.0 haskelldb-hdbc-0.10 haskelldb-hdbc-postgresql-0.10 Note you might have to modify the haskelldb cabal files to get them to use later versions of HDBC. As for recent documentation, unfortunately the darcs repository and the code is the best place to go. The haddock documentation doesn't have everything. Finally, I'd suggest joining the haskell-db users mailing list for specific questions. You can find info about that and the darcs repository on the homepage at http://haskelldb.sourceforge.net. Justin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] libmad and os/x coreaudio wrappers
On 2008.03.19 11:09:00 -0700, Chris Waterson [EMAIL PROTECTED] scribbled 1.7K characters: Hi there! I've taken my first stab at writing some (admittedly minimal) libraries for Haskell, and would love to get feedback on them: * hmad: a wrapper for the libmad MP3 decoder. http://maubi.net/~waterson/REPO/hmad * CoreAudio: a wrapper for OS/X CoreAudio. http://maubi.net/~waterson/REPO/CoreAudio (You should be able to darcs get the above links, if you want.) I wrote the libmad wrapper to generate a stream (i.e., a lazy list) of audio samples. CoreAudio allows the input stream to be lazy, as well. So, here's a simple MP3 player: module Main where import Sound.CoreAudio import Codec.Audio.MP3.Mad import qualified Data.ByteString.Lazy as B import System import System.IO main :: IO () main = do files - getArgs mapM_ playFile files playFile :: String - IO () playFile file = withBinaryFile file ReadMode $ \ inHandle - do xs - B.hGetContents inHandle samples - decode xs play samples I do have a couple questions... * The CoreAudio library requires its users to be compiled with -threaded. Is there a way to specify that in the Cabal file? I don't think so. Actually, I asked dcoutts, and he said Cabal cannot make a user use a specified ghc-option:. Apparently it did once, but it was abused and got removed: The only problem is that threaded applies to the final program. If a library declares that it needs threaded, does that mean we have to propagate the flag and use it with all programs that use it? Propagating GHC flags is not possible currently - by design. GHC used to have such a feature and it was removed. Or perhaps we say it's an extension that only applies to executables? http://hackage.haskell.org/trac/hackage/ticket/26 ... chris -- gwern enigma main Warfare DREC Intiso cards kilderkin Crypto Waihopai Oscor pgpH7st3jXs1S.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: HFuse: ls fails in HelloFS
On 2008.03.19 02:43:27 -0400, Brandon S. Allbery KF8NH [EMAIL PROTECTED] scribbled 0.8K characters: On Mar 19, 2008, at 2:12 , Austin Seipp wrote: Excerpts from Will Thompson's message of Sun Mar 16 08:37:00 -0500 2008: Currently the module's name is HFuse. Presumably it really belongs under System somewhere; System.Posix.Fuse maybe? What do folks think? Are there any guidelines for picking a namespace? I don't think there's any sort of doc on picking a namespace or how to logically name your package modules (would likely be worth writing); for something like this, I would say something under System.Posix.* would be the most appropriate. Erm, POSIX does not mean Linux and sufficiently similar systems. FUSE is supported by open source Unixlikes, not by POSIX compliant systems in general. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] [EMAIL PROTECTED] Not sure that's a useful distinction to make. Wikipedia says FUSE is available for Linux, FreeBSD, NetBSD (as PUFFS), OpenSolaris and Mac OS X (as MacFUSE). Linux, the BSDs, and Solaris are all pretty POSIX compliant, where they have not actually been officially certified by POSIX; OS X Leopard is surprisingly enough, certified - http://www.apple.com/macosx/technology/unix.html says Leopard is an Open Brand UNIX 03 Registered Product, conforming to the SUSv3 and POSIX 1003.1 specifications for the C API, Shell Utilities, and Threads. Since Leopard can compile and run all your existing UNIX code, you can deploy it in environments that demand full conformance — complete with hooks to maintain compatibility with existing software. Since there's no Filesystem.* hierarchy, what's wrong with System.Posix.FUSE.*? I know of no non-Posix systems that run FUSE... -- gwern enigma main Warfare DREC Intiso cards kilderkin Crypto Waihopai Oscor pgpcfkv27PFZf.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Error handling in calculations
L.S., When playing with exceptions, I noticed the following strangeness: *Main 1 / 0 Infinity *Main 1 `div` 0 *** Exception: divide by zero This is in GHCi 6.8.2; WinHugs Sep 2006 gives: Main 1 / 0 1.#INF Main 1 `div` 0 Program error: divide by zero Is this difference between fractional and integral calculation intentional? It makes error handling more difficult. -- Met vriendelijke groet, Henk-Jan van Tuyl -- http://functor.bamikanarie.com http://Van.Tuyl.eu/ -- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Error handling in calculations
* [EMAIL PROTECTED] [EMAIL PROTECTED] [2008-03-19 21:47:52+0100] L.S., When playing with exceptions, I noticed the following strangeness: *Main 1 / 0 Infinity *Main 1 `div` 0 *** Exception: divide by zero This is in GHCi 6.8.2; WinHugs Sep 2006 gives: Main 1 / 0 1.#INF Main 1 `div` 0 Program error: divide by zero Is this difference between fractional and integral calculation intentional? It makes error handling more difficult. I think it's because in the first case you have floating-point overflow (which can happen not just in case of division by 0 and means some very-large number -- remember, you cannot distinguish 0 and 0.00..001) and in the second case it's just division by zero -- meaningless operation. -- Roman I. Cheplyaka :: http://ro-che.info/ ...being in love is totally punk rock... signature.asc Description: Digital signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Type parameters in type families
Ryan Ingram: On 3/17/08, Hugo Pacheco [EMAIL PROTECTED] wrote: On the other side, it fails to compile when this signature is explicit: fff :: forall d x. (FunctorF d) = d - F d x - F d x fff a = fmapF a id Interestingly, this works when you also give a type signature to id: fff :: forall d x. (FunctorF d) = d - F d x - F d x fff a = fmapF a (id :: x - x) compiles for me (ghc6.8.2). There's probably a bug in the type checker; inference is working with no type signatures, but checking fails. The type checker is alright. It is an issue that we need to explain better in the documentation, though. As a simple example consider, class C a where type F a :: * foo :: F a The only occurrence of 'a' here is as an argument of the type family F. However, as discussed in this thread, decomposition does not hold for the type-indicies of a type family. In other words, from F a ~ F b, we can *not* deduce a ~ b. You have got the same situation for the 'x' in type type of fff. BTW, the same applies if you code the example with FDs. class C a ca | a - ca where foo :: ca which means, we have foo :: C a ca = ca Here 'a' only appears in the context and as 'a' appears on the lhs of the FD arrow, that leads to ambiguities. In summary, a type variable in a signature that appears *only* as part of type-indicies of type families leads to the same sort of ambiguities as a type variable that appears only in the context of a type signature. Manuel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
