[Haskell-cafe] libmad and os/x coreaudio wrappers

[gwern0 at gmail.com]

On 2008.03.19 11:09:00 -0700, Chris Waterson <waterson at maubi.net> 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
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