Re: [Haskell-cafe] Typechecking Using GHC API
On Tue, 13 Dec 2011 18:16:17 +0100, Sh NJP shayan@gmail.com wrote: I do some pre-processing on a normal Haskell code ( -F ). The pre-processor needs to know the type of each expression. What are the possibilities to do so? Can I use GHC API to employ GHC type checker? If yes, any good tutorial? Is it too naive to think of a function, f :: String - AnnotatedAST , that takes Haskell code and returns its corresponding abstract syntax tree annotated with types? Another, less powerful, but much easier approach would be to use hint, which also provides some type-checking functionality. Unfortunately, the results seem to be just Strings: http://hackage.haskell.org/packages/archive/hint/0.3.3.3/doc/html/Language-Haskell-Interpreter.html#g:7 If you want to see more examples of using the GHC API, you could also take a look at the ghc-mod repository on github, which uses the GHC API to provide type information to Emacs: https://github.com/kazu-yamamoto/ghc-mod Cheers, Daniel pgpBVUtUkkqQF.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] German names for kinds and sorts
On Sat, 12 Nov 2011 17:05:51 +0100, Robert Clausecker fuz...@gmail.com wrote: Most time, it is not really difficult to find an appropriate term for concepts of Haskell, like types (Typen) or type classes (Typklassen). But I really don't know how to call kinds and sorts in German. Any ideas? I'd go with Arten and Sorten respectively. Cheers, Daniel pgpkgjyy8iFEB.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Easiest to use NoSQL storage with Haskell?
On Wed, 9 Nov 2011 20:34:11 +0300, dokondr doko...@gmail.com wrote: I am wondering if Database.Persist can work with key/value storage such as Riak or SimpleDB where records are lists of key/value pairs and any two lists can have different keys? Is simple implementation of 'persistent' based on files with key/value records possible? For example 'persistent' based on KyotoCabinet package? (http://hackage.haskell.org/package/KyotoCabinet)http://hackage.haskell.org/package/KyotoCabinet As far as I know, persistent doesn't depend on any particular backend, but as far as NoSQL-stuff goes, I think there's only persistent-mongodb at the moment. I don't know how much work it is to create a new backend (and if it's worth the effort in your case), but this looks like a good place to start: http://hackage.haskell.org/packages/archive/persistent/0.6.4/doc/html/Database-Persist.html#t:PersistBackend Cheers, Daniel pgpJFU0H52TZ9.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Easiest to use NoSQL storage with Haskell?
On Wed, 9 Nov 2011 13:59:46 +0300, dokondr doko...@gmail.com wrote: Hi, What Haskell package to work with NoSQL storage is both mature and easiest to use? I need persistent storage for simple key/value lists (not complex JSON docs). CouchDB and Cassandra seems to be overkill for my needs. What about Riak, MongoDB, Voldemort, etc. ? persistent (part of yesod, but useable without other yesod libraries) is quite pleasant to use and supports MongoDB: http://hackage.haskell.org/package/persistent-0.6.4 http://hackage.haskell.org/package/persistent-mongoDB-0.6.3 Cheers, Daniel pgpOrSLejqLG4.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] howto best use emacs + tiling WM (Xmonad,DWM)
On Fri, 4 Nov 2011 11:24:37 -0700, Jason Dagit dag...@gmail.com wrote: The default buffer manipulation in emacs is not great. Take a look at things like ido mode: http://www.emacswiki.org/emacs/InteractivelyDoThings It's approximately 3 orders of magnitude better than the default way :) And anything is even better than that in my opinion: http://www.emacswiki.org/emacs/Anything `anything-buffers+' from anything-config.el makes switching between buffers a breeze. Cheers, Daniel pgpkgiMradBZk.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is there a DFA library?
On Fri, 7 Oct 2011 15:29:50 -0400, Alex Rozenshteyn rpglove...@gmail.com wrote: I'm looking for things like minimization, completion, etc. kinda like http://www.cis.upenn.edu/~cis639/docs/xfst.html This library's main purpose seems to be educational, but perhaps it's useful to you anyway: http://www3.di.uminho.pt/~jas/Research/HaLeX/HaLeX.html http://hackage.haskell.org/package/HaLeX Cheers, Daniel pgpN2L7oYwudk.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] class and instance
On Sun, 10 Jul 2011 11:49:44 +0100, Patrick Browne patrick.bro...@dit.ie wrote: My main question is in understanding the relationship between the arguments of the functions getX and getY in the class and in the instance. It seems to me that the constructor Pt 1 2 produces one element of type Point which has two components. How does this square with the class definition of getX which has two arguments? Is there a difference between: getX :: p a - a This applies the type constructor p, in this case Point to the type variable a. It is not a function that takes two arguments. A minor clarification: Pt 1 2 produces a value of type (Num a) = Point a, so a type where the type constructor Point is already applied to something. Just Point is not a valid type a value can have, but something that you have to apply to another type, called a type constructor. and getX :: p - a - a This is a function that takes two arguments. Cheers, Daniel pgpHx4UHpkIaI.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Class and Instance
On Fri, 10 Jun 2011 17:28:22 +0100, Patrick Browne patrick.bro...@dit.ie wrote: -- Not OK -- insert 2 [9,2] This causes an error, because numeric literals like 2 are polymorphic: :t 2 2 :: Num a = a If you fix the type to Integer, it works as expected: insert (2 :: Integer) [9,2] By the way: It's helpful to include the error messages in your mail when some piece of code doesn't compile. Cheers, Daniel pgpiVLpuLW0ar.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Comment Syntax
On Fri, 03 Jun 2011 12:19:31 +0300, Guy guytsalmave...@yahoo.com wrote: On 03/06/2011 12:01, Malcolm Wallace wrote: I believe the motivating example that persuaded the Language Committee to allow these symbols was -- which is not of course used anywhere in the standard libraries, but is an extremely nice symbol to have available in user code. Seeing as no library actually defines such a symbol, is it worth forcing an extra space into comments? [..] That's not true, xmonad[0] for example defines a ---operator; and I would find making exceptions for --| and --^ very inconsistent and annoying. [0] http://xmonad.org/xmonad-docs/xmonad/XMonad-ManageHook.html#v%3A--%3E pgp8FyrB33uh7.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] trying to use Tag Soup - fromAttrib
Excerpts from Michael Litchard's message of Tue Nov 02 22:40:27 +0100 2010: Daniel, Thank you for your reply. I'm still confused. When I see a code sample like this main = do posts - liftM parseTags (readFile posts.xml) print $ head $ map (fromAttrib Id) $ filter (~== (row OwnerUserId= ++ userid ++ )) posts I have no idea how to match that up with what you said. The usage of fromAttrib here doesn't match up with what I htink the type signature is saying. fromAttrib :: (Show str, Eq str, StringLike str) = str - Tag str - str seems to say fromAttrib takes two parameters (I know it doesn't literally take two), one str (with the constraints in parenthesis to the left) and one str of type Tag, giving back a str. Then I look at the above code sample and can't match the two up. In the code sample, the first argument is Id, in which case the concrete type for the type variable str is String, and the second argument are the tags returned by the call to filter, which have type Tag String. The second parameter is not a str of type Tag, but Tag (which is a type constructor) applied to the same concrete type for str its first argument has. So in your case, calling fromAttrib href (TagOpen ...) Would give you /launchWebForward.do?resourceId=4policy=0returnTo=%2FshowWebForwards.do. To get the resourceId you want, you'd have to dissect this string further. signature.asc Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] a way to convert partial functions to functions with Maybe's
Excerpts from Ozgur Akgun's message of Tue Apr 13 12:02:06 +0200 2010: Cafe, Is there a way (without going into the IO lands) to achieve this: [..] There's package for that on hackage: http://hackage.haskell.org/packages/archive/spoon/0.3/doc/html/Control-Spoon.html However, this is somewhat controversial regarding _|_: http://www.reddit.com/r/haskell/comments/acasn/tired_of_functions_that_could_live_in_maybe_but/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] n00b question: defining datatype
On Thu, Jul 23, 2009 at 08:17:34PM +0100, Iain Barnett wrote: [..] against the empty list it's not really a problem to have it there. I didn't realise I could use Maybe in the constructor because it's a monad, but that's good because I was wondering about the best way to make a nullable value. Actually, this has nothing to do with Maybe being a monad. The reason you can do this is because Maybe itself is not a type, but a (unary) type constructor(It has kind * - *), so you need to apply it to another type. Doing something like test :: Maybe would be an error. That Data.Tree module looks interesting too! It does seem to be a naturally recursive type, but I'm still trying to become easy with that sort of thought :) [..] A list is also recursively defined, so it is not really more difficult to use a Tree instead. E.g. one could define a list type like this: data List a = Nil | Cons a (List a) - Daniel pgpx25fhhGIwn.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
