December 2008 - Haskell-Cafe

Re: Re[2]: [Haskell-cafe] Data.ByteString join
by Galchin, Vasili 28 Dec '08

28 Dec '08

ooops ... .my bad ... so I guess Hoogle is the way to go?? On Sun, Dec 28, 2008 at 5:39 AM, Bulat Ziganshin <bulat.ziganshin(a)gmail.com>wrote: > Hello Vasili, > > Sunday, December 28, 2008, 1:59:43 PM, you wrote: > > > http://cvs.haskell.org/Hugs/pages/libraries/base/Data-ByteString.html > > look carefully - it's hugs docs > > > -- > Best regards, > Bulat mailto:Bulat.Ziganshin@gmail.com > >

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Re: Missing Network Functions
by John Van Enk 28 Dec '08

28 Dec '08

I want to group them with Network functions because traditionally these specific functions *are* in networking packages. On *nix systems, the prototypes reside in <netinet/in.h>. On Windows they reside in <winsock2.h> and one must link against libws2_32. The package I have locally supports all platforms. It just does a foreign import of the function (and uses a preprocessor definition to pick the calling convention). One could make an argument to add these sorts of functions to Word and Int packages. /jve On Sat, Dec 27, 2008 at 7:14 PM, Chris Kuklewicz < haskell(a)list.mightyreason.com> wrote: > Are these going to be available on Windows or just Posix systems? > > And these are NOT performing network communication. They are bit > manipulations. > > I could imagine putting them in/under the Data.Word or Data.Bits more than > Network.* > > And they should also be made to work with the corresponding Foreign.C.Types > of CShort, etc. > > > John Van Enk wrote: > >> While working on a project, I discovered that hton[sl] and ntoh[sl] are >> missing from the networking libraries. It appears there was some >> justification for this, but I've fallen upon a few instances where things >> were *not* working as expected. (Specifically when newtype'ing around >> HostAddress.) >> >> As such, I'm putting together a few extra functions that I think should >> exist in Network somewhere. I'm calling the package Network.Util (but am >> open to changes). >> >> Currently this only has: >> >> * htons >> * htonl >> * ntohs >> * ntohl >> >> Before I drop this on hackage: >> >> 1. Is there a reason I shouldn't do this? >> 2. Are there other suggestions for missing functions? (preferably >> cross-platform suggestions) >> >> Thanks all. >> >> /jve >> >> >> ------------------------------------------------------------------------ >> >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe >> > >

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Re: [Haskell-cafe] ByteString typechecking issues....
by Galchin, Vasili 27 Dec '08

27 Dec '08

Not in scope: `Data.ByteString.join' when Data.ByteString.join $ encode (buildHeader ss) -- ByteString -- [] (map encode (buildEntries (sequenceListExtract ss))) -- [ByteString] ?? Thanks, guys On Sat, Dec 27, 2008 at 3:13 AM, Eugene Kirpichov <ekirpichov(a)gmail.com>wrote: > I think Luke meant that you forgot to qualify the import for join, and > the compiler guessed that you are meaning the monad one, thus the > error. > > 2008/12/27 Galchin, Vasili <vigalchin(a)gmail.com>: > > Hi Luke, > > > > join :: ByteString -> [ByteString] -> ByteString ??? > > > > Vasili > > > > On Sat, Dec 27, 2008 at 1:58 AM, Luke Palmer <lrpalmer(a)gmail.com> wrote: > >> > >> 2008/12/26 Galchin, Vasili <vigalchin(a)gmail.com> > >>> > >>> Hello, > >>> > >>> I have a ByteString -> [ByteString] -> ByteString situation, i.e. > >>> concatenation ..... > >>> > >>> > >>> -- marshall into ByteString representation > >>> join > >>> (encode (buildHeader > >>> ss)) -- ByteString > >>> (map encode (buildEntries (sequenceListExtract > >>> ss))) -- [ByteString] > >>> > >>> > >>> I get the following typecheck error which is vexing me .... > >>> > >>> Couldn't match expected type `t -> t -> B.ByteString' > >>> against inferred type `B.ByteString' > >>> > >>> ??? > >> > >> join is not a function in Data.ByteString. By the error I'm guessing > >> you're getting the join from Control.Monad, instantiated to (->). > >> You are looking for "concat"; i.e. > >> concat $ > >> encode (buildHeader ss) : > >> -- ByteString > >> map encode (buildEntries (sequenceListExtract ss)) > >> -- [ByteString] > >> > >> (Control.Monad.join does end up meaning"concat" when working on lists of > >> lists, but it does not generalize to lists of other things). > >> Luke > > > > _______________________________________________ > > Haskell-Cafe mailing list > > Haskell-Cafe(a)haskell.org > > http://www.haskell.org/mailman/listinfo/haskell-cafe > > > > >

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Re: [Haskell-cafe] Re: [Haskell] ANN: HLint 1.0
by Claus Reinke 27 Dec '08

27 Dec '08

>> You were asking about getting the output of ':show modules' into a >> variable 'x', so that you can process it further. ':redir x :show modules' >> should do just that. There is another example command for implementing >> ':edit' this way (by now a native ghci command). > > I think I'm seeing your meaning. So that brings me up to this: > > let hlint _ = return $ unlines [":redir hlintvar1 :show modules", "let > hlintvar2 = map (fst . break (==',') . drop 2 . snd . break (== '(')) > $ lines hlintvar1", ":! hlint (concat $ intersperse \" \" hlintvar2"] > :def hlint hlint > > This doesn't work. The issue is that :! is weird; for it to work, one > need to pass each argument as a separate string, and it won't evaluate > a variable. It isn't just ':!', quoting/variable interpretation is generally rather uncomfortable in GHCi scripting (so much so that I originally submitted output redirection as a patch before figuring out that it could be done without patching GHCi - that surprise find was the motivation for posting my findings as an email). Have you tried reading the mini tutorial that I keep mentioning and which the "using GHCi" page is pointing to? Here's the direct link: http://www.haskell.org/pipermail/haskell-cafe/2007-September/032260.html The discussion is rather brief, but that tutorial has several examples that need to work around issues like this, ranging from simple but tedious construct-the-command-string to extra levels of ':cmd' in order to get extra levels of interpretation (when you need to construct a command string from a variable that will be bound via a constructed command string (see the definitions of ':find', ':le' or ':b(rowse)' - the latter is an example of using the info from ':show modules'). Claus

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Don't make 'show*' functions
by Thomas DuBuisson 27 Dec '08

27 Dec '08

Hello cafe, This is just a small thought, but its been bugging me. We have these things called type classes for a reason (I like to think). When making a new data type 'Data', it is not productive to avoid type classes such as 'Show' and export a 'showData' function. Examples of what I'm talking about include showHtml, showTrie, showInstalledPackageInfo... I know the default derivation (and thus generally accepted) instance of Show isn't pretty, but that just means to me that we need either more methods within the Show type class or start using the prettyclass package more. If the problem is an API issue lets fix Pretty or Show. But this show* stuff should disappear in the long run. Tom

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Typeclass question
by Andrew Wagner 27 Dec '08

27 Dec '08

I'm sure there's a way to do this, but it's escaping me at present. I want to do something like this: data Foo = Bar a => Foo a Bool ... That is, I want to create a new type, Foo, whose constructor takes both a Boolean and a value of a type of class Bar.

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ANNOUNCE: citeproc-hs-0.2
by Andrea Rossato 27 Dec '08

27 Dec '08

Hello, I'm happy to announce the release of citeproc-hs-0.2. WHAT'S NEW 1. Added support for citation collapsing options. This fills the last major gap to a usable CSL implementation; 2. added a wrapper around hs-bibutils[1] (disabled by default). By installing hs-bibutils and linking citeproc-hs to it with the '-fbibutils' configuration flag, it is possible to read all the bibliographic databases supported by bibutils[2]; 3. added some haddock API documentation: http://code.haskell.org/citeproc-hs/docs/ 4. simplified and started to document the internals of the library. DOWNLOADS citeproc-hs can be downloaded from Hackage: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/citeproc-hs ABOUT citeproc-hs is a Haskell implementation of the Citation Style Language. It adds to pandoc, the famous Haskell text processing tool, a Bibtex like citation and bibliographic formatting and generation facility. The Citation Style Language (CSL) is an XML language for specifying citation and bibliographic formatting, similar in principle to BibTeX .bst files or the binary style files in commercial products like Endnote or Reference Manager. CSL is used by Zotero for bibliographic style formatting, and a huge number of CSL styles have been developed by the Zotero community. More information, with installation instructions, can be found here: http://code.haskell.org/citeproc-hs/ Hope you'll enjoy, Andrea Rossato [1] http://code.haskell.org/hs-bibutils/ [2] http://www.scripps.edu/~cdputnam/software/bibutils/

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ANNOUNCE: hs-bibutils-0.1
by Andrea Rossato 27 Dec '08

27 Dec '08

Hello, I'm happy to announce the first release of hs-bibutils, the Haskell bindings to Chris Putnam's bibutils.[1] Bibutils is a library and a set of bibliographic utilities to interconvert between various bibliography database formats using a common MODS-format XML intermediate. hs-bibutils is meant to provide to citeproc-hs, and indirectly to pandoc, the ability to parse all the bibliographic database formats supported by bibutils. citeproc-hs[2] is a Haskell implementation of the Citation Style Language. It adds to pandoc a Bibtex like citation and bibliographic formatting and generation facility. DOWNLOADS hs-bibutils can be downloaded from Hackage: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hs-bibutils The project home page can be found here: http://code.haskell.org/hs-bibutils/ INSTALLATION AND KNOWN ISSUES bibutils builds, without installing it, a static library to be used to compile the various converting utilities. But in order to use the library with pandoc (or ghci) it is necessary to create and install a shared object before building and installing hs-bibutils. hs-bibutils provides a patch to the bibutils building scripts to enable the shared object creation and installation. Alternatively a patched version of the latest release of bibutils can be downloaded from the project home page, where all the needed information for the installation are provided: http://code.haskell.org/hs-bibutils/#installation I was able to test the patched building scripts only on a Linux machine with a x86 system. Please report me any success or failure on other systems/architectures. BUG REPORTS To submit bug reports you can either contact me directly or use the citeproc-hs bug tracking system available at the following address: http://code.google.com/p/citeproc-hs/issues Hope you'll enjoy, Andrea Rossato [1] http://www.scripps.edu/~cdputnam/software/bibutils/ [2] http://code.haskell.org/citeproc-hs/

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ByteString typechecking issues....
by Galchin, Vasili 27 Dec '08

27 Dec '08

Hello, I have a ByteString -> [ByteString] -> ByteString situation, i.e. concatenation ..... -- marshall into ByteString representation join (encode (buildHeader ss)) -- ByteString (map encode (buildEntries (sequenceListExtract ss))) -- [ByteString] I get the following typecheck error which is vexing me .... Couldn't match expected type `t -> t -> B.ByteString' against inferred type `B.ByteString' ??? Thanks, Vasili

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Type classes
by Oscar Picasso 27 Dec '08

27 Dec '08

>From Real World Haskell: data JValue = JString String | JNumber Double | JBool Bool | JNull | JObject [(String, JValue)] | JArray [JValue] deriving (Eq, Ord, Show) .... type JSONError = String class JSON a where toJValue :: a -> JValue fromJValue :: JValue -> Either JSONError a instance JSON JValue where toJValue = id -- Really ? fromJValue = Right Now, instead of applying a constructor like JNumber to a value to wrap it, > we apply the toJValue function. If we change a value's type, the compiler > will choose a suitable implementation of toJValue to use with it. Actually it does not work. And I don't see how it could with this toJValue implementation. Is it possible to make it work by providing another implementation? Oscar

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