June 2010 - Haskell-Cafe

TagSoup 0.9
by Ralph Hodgson 02 Jun '10

02 Jun '10

Hello Neil , I was using TagSoup 0.8 with great success. On upgrading to 0.9 I have this error: TQ\TagSoup\TagSoupExtensions.lhs:29:17: `Tag' is not applied to enough type arguments Expected kind `*', but `Tag' has kind `* -> *' In the type synonym declaration for `Bundle' Failed, modules loaded: TQ.Common.TextAndListHandling. where line 29 is the type declaration for 'bundle' in the following code: > module TQ.TagSoup.TagSoupExtensions where > import TQ.Common.TextAndListHandling > import Text.HTML.TagSoup > import Text.HTML.Download > import Control.Monad > import Data.List > import Data.Char > type Bundle = [Tag] [snip] > tagsOnPage :: String -> IO(String) > tagsOnPage url = do > tags <- liftM parseTags $ openURL url > let results = unlines $ map(show) $ tags > return (results) > extractTags :: Tag -> Tag -> [Tag] -> [Tag] > extractTags fromTag toTag tags = takeWhile (~/= toTag ) $ dropWhile (~/= fromTag ) tags > extractTagsBetween :: Tag -> [Tag] -> [Tag] > extractTagsBetween _ [] = [] > extractTagsBetween markerTag tags = if startTags == [] > then [] > else [head startTags] ++ (takeWhile (~/= markerTag ) $ tail startTags) > where > startTags = dropWhile (~/= markerTag ) tags I need to repair this code quickly. I am hoping you can quickly help me resolve this. Thanks. Ralph Hodgson, @ralphtq <http://twitter.com/ralphtq>

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Re: The state of Hackage: what are we doing about it?
by Bas van Dijk 01 Jun '10

01 Jun '10

On Tue, Jun 1, 2010 at 7:09 PM, Matthias Kilian <kili(a)outback.escape.de> wrote: > - "Liveness" of a library, that is: does it still get updates? Does it > build with recent versions of GHC? Note that Hackage already shows the upload date and for which versions of GHC the package does and doesn't build. > - Reverse dependencies -- how many other libraries and/or programs are > using this library (Maybe something for Hackage-2.0)? My brother Roel created a patch for this. See ticket #576: http://hackage.haskell.org/trac/hackage/ticket/576 Also see our mirror Hackage that implements that patch: http://bifunctor.homelinux.net/~roel/hackage/packages/hackage.html The server automatically synchronizes with Hackage daily. It would be great to have this in the regular Hackage however! Regards, Bas

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Re: Language Shootout reverse-complement benchmark
by Isaac Gouy 01 Jun '10

01 Jun '10

On Tue, Jun 1, 2010 at 10:25 AM, David Leimbach <leimy2k <at> gmail.com> wrote: > I'm still trying to figure out what the point of the shootout really is. >From one point of view - http://shootout.alioth.debian.org/help.php#why > If there's no dedicated folks working with a language there, trying to > make things run faster, a language will come out looking inefficient > potentially. If there isn't even one effective programmer willing to contribute tiny programs ... > There's a lot of compile flags and optimizations that can make a > difference in probably all of the languages listed on that page. The compile flags and optimizations used are shown below the program source code.

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Pugs with GHC 6.12
by Simon Thompson 01 Jun '10

01 Jun '10

Has anyone successfully compiled Pugs with GHC 6.12? The Pugs page suggests that it compiles, but it falls to link (and therefore build) when I try it. Thanks! Simon T.

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Haskell + CouchDB, anyone?
by Clint Moore 01 Jun '10

01 Jun '10

Hi there, I'm trying to use any version of couchdb with Haskell and Database.CouchDB and I'm not having a ton of luck. I've talked to others in the past that have used it without a problem so I'm wondering what it is that I'm doing wrong. I can connect, and create new databases without a problem - do any of you couchdb-using haskell people see a problem with this line? runCouchDB' $ newDoc (db "testify") $ JSObject $ toJSObject [("name",JSString $ toJSString $ "value")] I figured I would start small and just try to put something basic into a document. The rest of this email is also at a gist at http://gist.github.com/417442 Here is a list of the revisions of couchdb and the different errors I'm getting back as well as some of the code I'm using to try to test this.. Hopefully it will help. {- CouchDB 0.11.0: [error] [<0.95.0>] attempted upload of invalid JSON undefined [info] [<0.95.0>] 127.0.0.1 - - 'PUT' /honks/cmoore? 400 CouchDB Trunk as of 5/28 - 10:26 PST: [info] [<0.95.0>] 127.0.0.1 - - 'PUT' /honks? 201 [debug] [<0.114.0>] 'PUT' /honks/cmoore? {1,1} Headers: [{'Connection',"keep-alive"}, {'Content-Type',"application/json"}, {'Host',"localhost:5984"}, {'User-Agent',"hs-HTTP-4000.0.5"}] [debug] [<0.114.0>] OAuth Params: [] [error] [<0.114.0>] attempted upload of invalid JSON undefined [info] [<0.114.0>] 127.0.0.1 - - 'PUT' /honks/cmoore? 400 [debug] [<0.114.0>] httpd 400 error response: {"error":"bad_request","reason":"invalid UTF-8 JSON"} CouchDB rev 818083: [debug] [<0.107.0>] 'PUT' /honks/cmoore? {1,1} Headers: [{'Connection',"keep-alive"}, {'Content-Type',"application/json"}, {'Host',"localhost:5984"}, {'User-Agent',"hs-HTTP-4000.0.5"}] [debug] [<0.107.0>] OAuth Params: [] [debug] [<0.107.0>] Minor error in HTTP request: {invalid_json,undefined} [debug] [<0.107.0>] Stacktrace: [{mochijson2,decode,1}, {couch_httpd_db,db_doc_req,3}, {couch_httpd_db,do_db_req,2}, {couch_httpd,handle_request,5}, {mochiweb_http,headers,5}, {proc_lib,init_p_do_apply,3}] [info] [<0.107.0>] 127.0.0.1 - - 'PUT' /honks/cmoore? 500 [debug] [<0.107.0>] httpd 500 error response: {"error":"invalid_json","reason":"undefined"} CouchDB 0.10.1: [error] [<0.278.0>] attempted upload of invalid JSON undefined [info] [<0.278.0>] 127.0.0.1 - - 'POST' /testify? 400 -} module Main where import Text.JSON import Database.CouchDB import Database.CouchDB.JSON data Person = Person { name :: String, email :: String } deriving (Eq,Show) instance JSON Person where showJSON (Person nm em) = JSObject $ toJSObject [("name", showJSON nm),("email", showJSON em)] readJSON val = do obj <- jsonObject val nm <- jsonField "name" obj em <- jsonField "email" obj return (Person nm em) create = runCouchDB "localhost" 5984 $ createDB "honks" main :: IO () main = do _ <- runCouchDB "localhost" 5984 $ newNamedDoc (db "honks") (doc "cmoore") $ Person "cmoore" "cmoore(a)w.com" putStrLn "Honk." --- Later, against 0.10.1: cmoore@cathedral:~/tmp$ ghci GHCi, version 6.12.2: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Loading package ffi-1.0 ... linking ... done. Prelude> :m +Database.CouchDB Prelude Database.CouchDB> :m +Text.JSON Prelude Database.CouchDB Text.JSON> :set prompt "> " > runCouchDB' $ createDB "testify" Loading package array-0.3.0.0 ... linking ... done. Loading package syb-0.1.0.2 ... linking ... done. Loading package base-3.0.3.2 ... linking ... done. Loading package bytestring-0.9.1.6 ... linking ... done. Loading package mtl-1.1.0.2 ... linking ... done. Loading package parsec-2.1.0.1 ... linking ... done. Loading package network-2.2.1.5 ... linking ... done. Loading package old-locale-1.0.0.2 ... linking ... done. Loading package old-time-1.0.0.4 ... linking ... done. Loading package HTTP-4000.0.8 ... linking ... done. Loading package containers-0.3.0.0 ... linking ... done. Loading package pretty-1.0.1.1 ... linking ... done. Loading package json-0.4.4 ... linking ... done. Loading package CouchDB-0.10.2 ... linking ... done. > runCouchDB' $ newDoc (db "testify") $ JSObject $ toJSObject [("name",JSString $ toJSString $ "value")] *** Exception: HTTP/1.1 400 Bad Request Server: CouchDB/0.10.1 (Erlang OTP/R13B) Date: Fri, 28 May 2010 18:46:36 GMT Content-Type: text/plain;charset=utf-8 Content-Length: 54 Cache-Control: must-revalidate

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name of this monadic combinator?
by Michael Vanier 31 May '10

31 May '10

I stumbled across this monadic combinator: mcombine :: Monad m => (a -> a -> a) -> m a -> m a -> m a mcombine f mx my = do x <- mx y <- my return (f x y) I used it to chain the outputs of two Parsec String parsers together using this operator: (<++>) :: Monad m => m String -> m String -> m String (<++>) = mcombine (++) mcombine seems like such a basic operation that it should be a library function, but I couldn't find one matching it on hoogle. Is there one? - Mike

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ANN: list-extras 0.4.0
by wren ng thornton 31 May '10

31 May '10

-------------------------------------------- -- list-extras 0.4.0 -------------------------------------------- A minor (but interface-changing) release for common not-so-common functions for lists. -------------------------------------------- -- Changes (since 0.3.0) -------------------------------------------- * (by Tom Lokhorst) Added Data.List.Extras.list: a function for non-recursive case matching on lists. In the spirit of `maybe` and `either` (if we don't interpret them as catamorphisms). * Changed the type of Data.List.Extras.Pair.zipBy to be correct. I have no idea where the old more restrictive type came from. -------------------------------------------- -- Links -------------------------------------------- Homepage: http://code.haskell.org/~wren/ Hackage: http://hackage.haskell.org/package/list-extras Darcs: http://code.haskell.org/~wren/list-extras/ Haddock (Darcs version): http://code.haskell.org/~wren/list-extras/dist/doc/html/list-extras/ -- Live well, ~wren

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