January 2011 - Haskell-Cafe

ArchLinux binary repository available for beta testing
by Peter Simons 11 Jan '11

11 Jan '11

Hi guys, those of you who use the ArchLinux distribution might be interested to know that a team of volunteers has put together a binary package repository that complements the set of Haskell packages that's already being distributed by ArchLinux. Subscribers of that repository can use Pacman to install all of Haskell Platform 2010.2.0.0 as well as a few other popular packages such as bnfc, hledger, pandoc, sifflet, and yesod on both i686 and x86_64. If you want to use the repository, then append the following two lines at the end of your /etc/pacman.conf file: [haskell] Server = http://andromeda.kiwilight.com/$repo/$arch Please be aware of the fact that this is the very first public announcement of this repository, so you should consider it as being in a kind of beta state. Basically, if your Linux machine is responsible for controlling some large nuclear power plant or something, you probably shouldn't be using this. Everyone else is encouraged to try it out. If you encounter problems, have questions, or would like to make suggestions, then please raise an issue at <https://github.com/archhaskell/habs/issues>. Of course, you're also welcome to provide feedback by posting to the haskell-cafe mailing list or to arch-haskell(a)haskell.org. Many people have contributed to this effort in one way or another. Don Stewart originally wrote the cabal2arch tool that is being used to generate the HABS tree on which this repository is based. Rémy Oudompheng has extended that tool and the underlying ArchLinux library significantly, and he has also written most of the build system that's being used to compile the binary packages. Magnus Therning has compiled all the x86_64 binaries. The i686 binaries were compiled by Yours Truely. Kaiting Chen is kindly hosting the repository on his server. Furthermore, there are many other people who have submitted bug reports, suggestions, and fixes by way of AUR. Have fun, Peter

1 0

Possible participation on parallel programming book
by Michael Oswald 11 Jan '11

11 Jan '11

Hello, Just found the following in the Ada group: There is an open source E-Book about parallel programming, where people can participate (via patches for a git repository): http://lwn.net/Articles/421425/ Since Haskell has very good parallel capabilities, maybe the community would also be interested in participating? lg, Michael

1 0

Re: [Haskell-cafe] [Haskell] School of Expression pages missing from haskell.org
by Henning Thielemann 11 Jan '11

11 Jan '11

On Tue, 11 Jan 2011, Julian Gilbey wrote: > Does anyone know what has happened to the Haskell School of Expression > (SOE) webpages? The link from books for learning Haskell now gives a > 404 Not Found error. Maybe caused by the recent server move.

1 0

Re: [Haskell-cafe] GHC.Ptr, Foreign.Storable, Data.Storable.Endian, looking for good examples of usage
by John Lato 11 Jan '11

11 Jan '11

> > On 10 January 2011 16:36, Antoine Latter <aslatter(a)gmail.com> wrote: > > > On Mon, Jan 10, 2011 at 10:17 AM, Aaron Gray <aaronngray.lists(a)gmail.com > > > > wrote: > > > On 10 January 2011 16:13, Daniel Fischer < > > daniel.is.fischer(a)googlemail.com> > > > wrote: > > >> > > >> On Monday 10 January 2011 16:45:36, Aaron Gray wrote: > > >> > > > >> > This is interesting, what does the following line do :- > > >> > > > >> > data Int24 = I24# Int# deriving (Eq, Ord) > > >> > > > >> > regarding the I24# and Int#, are these inbuilt ? > > >> > > >> Int# is the raw machine int (4 or 8 bytes) and I24# is the > constructor. > > >> GHC > > >> uses the magic hash '#' to denote raw unboxed types (and the > > constructors > > >> making ordinary boxed Haskell types from these, e.g. there's > > >> > > >> data Int = I# Int# > > >> data Word = W# Word# > > >> data Double = D# Double# > > >> > > >> and more defined in base [GHC.Types, GHC.Word]). > > > > > > So the 24 bit value is actually stored as a 32bit value. Meaning I will > > have > > > to do my own IO reader and writer code to a ByteString. > > > Thanks, > > > Aaron > > > > > > > I don't think so - the Storable instance provided for the Int24 type > > peeks and pokes 24-bit values. At least, that what I understand John's > > earlier message to mean. > > > Yes looking at the code it does support 24bit peeks and pokes. > This is correct (at least it's how it's meant to work). 24bit values are represented as 32bit words for ops, but peeks and pokes are 24bit. If all you want to do is read/write 24bit values there's nothing wrong with binary, but if you ever want to use them the Word24 and Int24 types are nice to have. John

1 0

Join Manatee Team!
by Andy Stewart 10 Jan '11

10 Jan '11

Hi all, I'm Andy, the author of Manatee ( http://haskell.org/haskellwiki/Manatee ). You can watch video http://www.youtube.com/watch?v=weS6zys3U8k (or http://www.youtube.com/watch?v=A3DgKDVkyeM ) to understand "What is it?" . :) Manatee is Haskell integrated environment written in Haskell. The goal of the Manatee project is provide a fast, safe and flexible integrated environment for haskell hacking. Some cool feature in Manatee: * It can dynamic update Haskell extension code in runtime, like elisp for Emacs. * It protected every application in sandbox, so it minimum your losses once unexpected exception throw. * It's multi-thread design, it's won't freeze your operation in anytime. * It provide handy window manage, you can mix any application together fastly. * You can use keyboard control everything you want, and same experience in all applications. :) * You can use it develop any application you want, not just text toy. :) ... etc. I'm looking for new developer join Manatee Team, I believe you guys can develop cooler application than me. :) If you interested Manatee, welcome to join manatee-user(a)googlegroups.com (or https://groups.google.com/forum/#!forum/manatee-user ) Thanks, -- Andy PS. I'm working on session manager and IDE feature...

2 4

ghci 6.12.3 segfaults for reasons unknown to me.
by Michael Litchard 10 Jan '11

10 Jan '11

mlitchard@kether:~/projects/perf/autoperf/session_creator/newtry2/strings$ ghci -v GHCi, version 6.12.3: http://www.haskell.org/ghc/ :? for help Glasgow Haskell Compiler, Version 6.12.3, for Haskell 98, stage 2 booted by GHC version 6.8.2 ghci was working a few weeks ago. I may have hidden a package or installed one to cause this segfault now. Could someone help me troubleshoot what is causing this? I did a stack trace but could not discern any useful info from it. Using binary package database: /usr/local/lib/ghc-6.12.3/package.conf.d/package.cache Using binary package database: /home/mlitchard/.ghc/x86_64-linux-6.12.3/package.conf.d/package.cache hiding package parsec-2.1.0.1 to avoid conflict with later version parsec-3.1.0 hiding package base-3.0.3.2 to avoid conflict with later version base-4.2.0.2 wired-in package ghc-prim mapped to ghc-prim-0.2.0.0-5da421112969a971aa3433fdf154b37a wired-in package integer-gmp mapped to integer-gmp-0.2.0.1-67f3940ec8fd509683668f40451c9ca1 wired-in package base mapped to base-4.2.0.2-cc69ae37cc080e111e11df0109986bd2 wired-in package rts mapped to builtin_rts wired-in package haskell98 mapped to haskell98-1.0.1.1-4d2891ad99eae334ff8234bcfbddce06 wired-in package template-haskell mapped to template-haskell-2.4.0.1-e9e9c63092746bd4a3f64cc37ddb1e06 wired-in package dph-seq mapped to dph-seq-0.4.0-5ed11291726022ff6bb22049478399e8 wired-in package dph-par mapped to dph-par-0.4.0-5a5a24e36763903b0b26f03d8d510a95 Hsc static flags: -static Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Loading package ffi-1.0 ... linking ... done. Segmentation fault

1 0

POPL 2011 Hotel Room
by Michael D. Adams 10 Jan '11

10 Jan '11

Hi all, I'm a graduate student (male) and am looking for a (male) roommate to split the cost of a hotel room at POPL. If anyone is interested in splitting a room, please drop me a line. I will be attending the workshops collocated with POPL so I currently have a reservation at the conference hotel (at the conference rate) with check-in on January 22 (the day before the first workshop) and check-out on January 30 (the day after the last workshop). Michael D. Adams Ph.D. Student, Indiana University

1 0

ANN: nanoparsec 0.1
by Maciej Piechotka 10 Jan '11

10 Jan '11

Nanoparsec is currently simply a port of attoparsec on the ListLike (the abstraction of lists used by iteratee). It allows to achive in parsing a near-attoparsec levels of speed (benchmarks from attoparsec library shown a 0.450 ± 0.028 for attoparsec, 0.479 ± 0.043 for nanoparsec and 1.532 ± 0.084 for parsec 3) combining the flexibility of stream of parsec 3 with the iterative approach and speed of attoparsec. Regards

2 2

How to write such a code elegantly ?
by z_axis 10 Jan '11

10 Jan '11

betterStdGen :: IO StdGen betterStdGen = alloca $ \p -> do h <- openBinaryFile "/dev/urandom" ReadMode hGetBuf h p $ sizeOf (undefined :: Int) hClose h mkStdGen <$> peek p picoSec :: IO Integer picoSec = do t <- ctPicosec `liftM` (getClockTime >>= toCalendarTime) return t The pseudo-code is : if doesFileExist "/dev/urandom" then myGen = betterStdGen else myGen = (mkStdGen . fromTnteger) <$> picoSec How to write these pseudo-code elegantly ? Sincerely! ----- e^(π.i) + 1 = 0 -- View this message in context: http://haskell.1045720.n5.nabble.com/How-to-write-such-a-code-elegantly-tp3… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

5 7

Draw K-ary forest in dot script
by larry.liuxinyu 10 Jan '11

10 Jan '11

Hi, I wrote a Haskell program to parse K-ary forest and convert it to dot script (Graphviz). Here is the literate program. -- First is some stuff imported: module Main where import System.Environment (getArgs) import Text.ParserCombinators.Parsec import Control.Monad (mapM_) import Data.List (concatMap, intercalate) import System.IO (writeFile) import Data.Char (isSpace) -- For each tree in the forest, it is described in pre-order. -- Example description string of a forest of CLRS[1] Figure 19.5(a): -- (12), (7, (25)), (15, (28, (41)), (33)) -- Definition of K-ary node data Node a = Node { root :: a , children :: [Node a]} deriving (Eq, Show) -- Definition of Forest type Forest a = [Node a] -- parsers -- a forest is a list of trees separate by ',' forest = do ts <- node `sepBy` (char ',') return ts -- a node contains a key then followed by a children forest or nothing (leaf case) node = do char '(' elem <- key ts <- (try (char ',')>>forest) <|> return [] char ')' return (Node elem ts) -- a key is just a plain literate string. key = many (noneOf ",()") -- Command line arguments handling parseArgs :: [String] -> (String, String) parseArgs [fname, s] = (fname, s) parseArgs _ = error "wrong usage\nexample:\nfr2dot output.dot \"(12), (7, (25)), (15, ((28, (41)), 33))\"" -- A simplified function to generate dot script from parsed result. toDot f = forestToDot f "t" True -- a handy function to convert children of a K-ary tree to dot script treesToDot ts prefix = forestToDot ts prefix False -- convert a forest to dot script forestToDot [] _ _ = "" forestToDot [t] prefix _ = nodeToDot t prefix forestToDot ts@(_:_:_) prefix lnk = (concatMap (\t->nodeToDot t prefix) ts) ++ consRoot where consRoot = "{rank=same " ++ ns ++ vis ++ "}\n" ns = intercalate "->" $ map (\t -> prefix ++ root t) ts vis = if lnk then "" else "[style=invis]" -- convert a node to dot script nodeToDot (Node x ts) prefix = prefix'++"[label=\""++x++"\"];\n" ++ (treesToDot ts prefix') ++ (defCons ts prefix') where prefix' = prefix ++ x -- define connections among nodes in dot format defCons ts prefix = concatMap f ts where f (Node x _) = prefix++"->"++prefix++x++";\n" -- generate dot script from a parsed forest genDot fname (Right f) = writeFile fname dots >> putStrLn dots where dots = "digraph G{\n\tnode[shape=circle]\n"++(addTab $ toDot f)++"}" addTab s = unlines $ map ("\t"++) (lines s) main = do args <- getArgs let (fname, s) = parseArgs args genDot fname (parse forest "unknown" (filter (not.isSpace) s)) -- END I tested with the following simple cases: ./fr2dot foo.dot "(12), (7, (25)), (15, (28, (41)), (33))" ./fr2dot bar.dot "(18), (3, (37)), (6, (8, (30, (45, (55)), (32)), (23, (24)), (22)), (29, (48, (50)), (31)), (10, (17)), (44))" Run the following commands can convert to PNG files: ./dot -Tpng -o foo.png foo.dot ./dot -Tpng -o bar.png bar.dot Reference: [1]. Thomas H. Cormen, Charles E. Leiserson, Ronald L. Rivest and Clifford Stein. ``Introduction to Algorithms, Second Edition''. The MIT Press, 2001. ISBN: 0262032937. Best regards. -- Larry, LIU https://sites.google.com/site/algoxy/home

2 1