December 2010 - Haskell-Cafe

Installing snap-server with gnutls on OS X with Homebrew
by Benedict Eastaugh 21 Dec '10

21 Dec '10

Hi -café, I installed Snap 0.3 last night on my Mac, and had some problems getting it to build with SSL support. This is just a quick note of the extra flags I had to pass in when installing it in case someone else has a setup similar to mine. These instructions presume that you are using the Homebrew package manager on OS X, and that Homebrew is installing packages into /usr/local. You first need to install the gnutls library. brew install gnutls Then install snap-server. cabal update cabal install snap-server -fgnutls --extra-lib-dirs=/usr/local/lib/ --extra-include-dirs=/usr/local/include/ Note that while gnutls' dependencies libgcrypt and libgpg-error also need to be in the path, they are dependencies of gnutls and will both be installed when you install gnutls with Homebrew. Cheers, Benedict.

1 0

internal Haddock or GHC error: de-package: openBinaryFile:
by Johannes Waldmann 21 Dec '10

21 Dec '10

Hi. I try to use haddock (2.8.1) but it breaks with haddock: internal Haddock or GHC error: de-package: openBinaryFile: does not exist (No such file or directory) Why would it want to read a file with the name "de-package"? (Is "de" related to the locale? But the error also happens with LC_ALL=C) If I do "touch de-package" in the current directory, then I get haddock: internal Haddock or GHC error: Data.Binary.getWord8: end of file I am running this in a directory where I did ghc --make before, and then haddock -d $(find . -name "*.hi" | sed -e 's/\.hi/.hs/') I can't try this with haddock-2.9 since I am using ghc-6.12.3 (?) Thanks, J.W.

1 0

Haskell Parse Tree
by Jane Ren 21 Dec '10

21 Dec '10

Hi, Does anyone know how to get the parse tree of a piece of Haskell code? Any recommended documentation? Thanks

4 3

ANNOUNCE: new version of uu-parsinglib:2.5.6
by S. Doaitse Swierstra 21 Dec '10

21 Dec '10

An old problem popped up in the uu-parsinglib. When combining two parsers with <|>, it is checked to see which alternative accepts the shortest input; this is done in order to prevent infinite insertions, which may occur as a result of choosing a recursive alternative when inserting of some recursive non-terminal is needed. In such a case we want to choose a non-recursive alternative. This approach however does not combine well with the permuting parsers: here all the alternatives have the same length and we do not want to compute all those lengths, since this defeats the whole purpose of building these permutations lazily. So I added a non-length-checking version of <|> to ExtApplicative with is used in pPerms. If you are using the permuting parsers you are strongly advised to upgrade. Have a nice Christmas and a happy new year, Doaitse

1 0

Data.Judy and StablePtr
by Diego Souza 21 Dec '10

21 Dec '10

Hello Haskellers, I'm playing a bit with Data.Judy. However, I noticed that using StablePtr incurs in some performance problems, I don't have any numbers but as a example use Int and ByteString as values and you can notice the difference without any benchmarking tool with the example that comes in the documentation. The question that I have is: is there any way to make it faster for types other than those that fits in word size? I understand that the way the binding to the C code has been done, stableptr is required. Am I wrong assuming this? I would be happy to submit a patch but I failed to find a way to improve the performance. The second question is what is a common practice to avoid memory leaks with StablePtr? I have zero experience programming with the Haskell FFI interface, so probably the most basic stuff would help me a lot in this case. Thanks in advance, -- ~dsouza yahoo!im: paravinicius gpg key fingerprint: 71B8 CE21 3A6E F894 5B1B 9ECE F88E 067F E891 651E gpg pub key: http://bitforest.org/~dsouza/pub/gpg-pubkey.txt authorized_keys: http://bitforest.org/~dsouza/pub/authorized_keys.txt

2 2

unable to load package `regex-posix-0.94.2' (On Vista x64)
by __kaveh__ 21 Dec '10

21 Dec '10

I am using Vista x64. I have Haskell platform installed (Latest varsion -available for Windows, 2010.2.0.0, GHC 6.12.3). When I am trying to run picnic.hs from "How To Organize a Picnic on a Computer" tutorial. I get this: C:\...>runhaskell picnic.hs picnic.hs:46:18: Warning: accepting non-standard pattern guards (use - XPatternGuards to suppr ess this message) Just [x, y] <- matchRegex (mkRegex "([0-9.]+), ([0-9.]+)") s picnic.hs:181:21: Warning: accepting non-standard pattern guards (use - XPatternGuards to suppr ess this message) Just (_, e) <- find ((== p) . fst) a picnic.hs: C:\Program Files (x86)\Haskell Platform\2010.2.0.0\lib \extralibs\rege x-posix-0.94.2\ghc-6.12.3\HSregex-posix-0.94.2.o: unknown symbol `_regerror' picnic.hs: picnic.hs: unable to load package `regex-posix-0.94.2' I have tried to update using (cmd is running as administrator): C:\Windows\system32>cabal update Downloading the latest package list from hackage.haskell.org And then installing package using cabal: C:\Windows\system32>cabal install regex-posix [--reinstall] --global Resolving dependencies... Configuring regex-posix-0.94.4... Preprocessing library regex-posix-0.94.4... Building regex-posix-0.94.4... [1 of 6] Compiling Text.Regex.Posix.Wrap ( dist\build\Text\Regex\Posix \Wrap.hs, dist\build\Text\Regex\Posix\Wrap.o ) [2 of 6] Compiling Text.Regex.Posix.String ( Text\Regex\Posix \String.hs, dist\bu ild\Text\Regex\Posix\String.o ) [3 of 6] Compiling Text.Regex.Posix.Sequence ( Text\Regex\Posix \Sequence.hs, dis t\build\Text\Regex\Posix\Sequence.o ) [4 of 6] Compiling Text.Regex.Posix.ByteString ( Text\Regex\Posix \ByteString.hs, dist\build\Text\Regex\Posix\ByteString.o ) [5 of 6] Compiling Text.Regex.Posix.ByteString.Lazy ( Text\Regex\Posix \ByteStrin g\Lazy.hs, dist\build\Text\Regex\Posix\ByteString\Lazy.o ) [6 of 6] Compiling Text.Regex.Posix ( Text\Regex\Posix.hs, dist\build \Text\Regex \Posix.o ) Registering regex-posix-0.94.4... Installing library in C:\Program Files (x86)\Haskell\regex-posix-0.94.4\ghc-6.12.3 Registering regex-posix-0.94.4... And why the cabal package installs at "C:\Program Files (x86)\Haskell"? Shouldn't it be "C:\Program Files (x86)\Haskell Platform\2010.2.0.0"? Thanks

3 6

identity function
by A Smith 21 Dec '10

21 Dec '10

I've been reviewing the library, and have come unstuck with the *id*function. What's its purpose and can someone give me an example of its practical use. -- Andrew

3 2

Where are all the Taiwanese Haskellers?
by Pasqualino "Titto" Assini 21 Dec '10

21 Dec '10

Hello, I am going to Taiwan with my family for about five weeks (I am Italian, my wife is Taiwanese and we have two kids) and I wondered if there was any Taiwanese Haskeller that would be interested in meeting for a chat about Haskell, Life and Everything else, maybe in front of a nice cup of 高山茶. We arrive in Taiwan on the 4th of December, spend a few days nearby Taipei and then down to Pu-Li and Kaoshong, where we will spend about 4 weeks and then probably back to Taipei for a few more days around the 10 of January. I am afraid that my Chinese is almost non-existent (yes I know, that's so stupid of me) so the conversation will have to be in English (Italian or French would be fine as well :-)). All the very best, titto -- Dr. Pasqualino "Titto" Assini http://quid2.org/

2 1

non-hackage cabal repos? unpacking non-repo package tarballs?
by Claus Reinke 20 Dec '10

20 Dec '10

I often find myself writing example code that I'd like to distribute via cabal, but without further burdening hackage with not generally useful packages. 1. The simplest approach would be if cabal could expose its internal 'unpackPackage' as a command, so that author: cabal sdist user: cabal unpackPackage Example.tar.gz would work (the point being that cabal handles .tar.gz, which not all users have installed separately; distributing the .tar.gz would be handled via the usual channels; and after unpacking, cabal can build the source package). Note that 'cabal unpack' does not seem helpful here, as it touches the package index instead of just looking at the tarball. Could this be made possible, please? Or is it already? 2. Failing that, I remembered that cabal used to be designed without a fixed package repo address, and a little digging found options --remote-repo and --local-repo, as well as the directory layout for package repositories: http://hackage.haskell.org/trac/hackage/wiki/HackageDB So this scenario seems possible, in principle: author: expose a package repo http://myrepo user: cabal --remote-repo=http://myrepo fetch Example Is it possible to add a (temporary) repo location like this, especially for 'cabal fetch'/'cabal unpack'? I've managed to get 'cabal --local-repo=myrepo list Example' to work (needs uncompressed 00-index.tar), but not the remote variant, and fetching from the local repo doesn't work, either. Are there any usage examples of these features? Claus

3 2

ANN: cabal-dev - sandboxed haskell development
by Rogan Creswick 20 Dec '10

20 Dec '10

Galois is happy to announce cabal-dev: a tool for managing development builds of Haskell projects within sandboxes. Performing consistent builds is critical in software development, but the current system in GHC/Haskell of per-user and per-system GHC package databases interferes with this need for consistency. It is difficult to precisely identify the dependencies of a given project, and changes necessary to enable one project to build may render another project inoperable. If each project had a separate package database, each project could be built in a sandbox. Cabal-dev manages cabal-install repositories and sandboxed ghc package databases to prevent interactions between disparate projects or user package databases. Cabal-dev is similar to capri, which was coincidentally developed concurrently, but the two projects take slightly different approaches to sandboxing and exhibit slightly different behaviors depending on the state of the global package database and the versions of the tools installed. For most packages, just use cabal-dev instead of cabal, and you will get a sandboxed build that will not install anything (even automatically installed dependencies) into the user or global ghc package databases. If your build depends on patched or unreleased libraries, you can add them to your sandboxed build environment so they can be installed by cabal-dev or cabal by running: > cabal-dev add-source /path/to/source/code Where /path/to/source/code is either a path to a source directory containing a .cabal file, or an sdist tarball. Cabal-dev has been in use at Galois for roughly six months now, but it should currently be treated as alpha software: we've exercised a few execution paths heavily, but it still has a number of rough edges (the rough edges we know about are documented in the TODO file: https://github.com/creswick/cabal-dev/blob/master/TODO.md) Cabal-dev is hosted on hackage and git-hub: - http://hackage.haskell.org/package/cabal-dev - https://github.com/creswick/cabal-dev A brief tutorial can be found in the README.md: - https://github.com/creswick/cabal-dev/blob/master/README.md We're looking forward to your feedback! --Rogan Creswick

1 0