Welcome to issue 110 of HWN, a newsletter covering developments in the Haskell community.

Facebook apps with Happstack, Sudoku with Cryptol, what next? Tic-tac-toe with darcs? Anyway, lots of neat stuff this week, including new releases of GHC, jhc, and the Monad.Reader, some fun visualizations, and more. Also, students: apply to work on a Haskell project for the Google Summer of Code!


GHC 6.10.2 Release Candidate 1. Ian Lynagh announced the first release candidate for GHC 6.10.2. Please test as much as possible; bugs are much cheaper if we find them before the release!

jhc 0.6.0 Haskell Compiler. John Meacham announced the release of jhc 0.6.0.

Safe Lazy IO in Haskell. Nicolas Pouillard announced the safe-lazy-io package that provides special types and combinators for performing safe lazy I/O.

game-tree - a library for searching game trees. Colin Paul Adams announced game-tree, which provides a class for dynamic game trees, and purely functional algorithms for searching them.

random-shuffle package. Manlio Perillo announced the availability of the random-shuffle package, which is based on Oleg's description.

random-stream package. Manlio Perillo announced the random-stream package, which provides a portable interface for the operating system source of pseudo random data. Supported sources are Unix /dev/urandom, Win32 CryptGenRandom and OpenSSL pseudo random numbers generator.

language-python. Bernie Pope announced the language-python package, which provides a parser (and lexer) for Python, written in Haskell. Currently it only supports version 3 of Python (the most recent version), but it will support version 2 in the future.

Google Summer of Code. Malcolm Wallace announced that haskell.org has once again been accepted as a mentoring organisation for the 2009 Google Summer of Code. Student applications open on Monday (23rd March) at 1900 UTC, for a period of 12 days (until Fri 3rd April, also at 1900 UTC). Students applicants are encouraged to interact with the community via mailing lists, prior, during, and after the submission of their ideas for projects. Because (sadly) the darcs community did not get accepted as a separate organisation this year, haskell.org will be willing to accept proposals relating to darcs.

regex-tdfa-1.1.0. ChrisK announced the release of regex-tdfa-1.1.0. This version is a small performance update to the old regex-tdfa-1.0.0 version. Previously all text (e.g. ByteString) being search was converted to String and sent through a single engine; the new version uses a type class and SPECIALIZE pragmas to avoid converting to String. This should make adding support for searching other Char containers easy to do.

Haskell on your system? Information wanted!. Don Stewart announced that haskell.org now features links to wiki pages explaining how to obtain Haskell on windows, mac osx and linux and bsd. If you're a distro maintainer for these systems, please consider adding relevant pointers to the pages, so that users of these systems can find all the info they need.

libffi 0.1 released. Remi Turk announced the release of libffi 0.1, bindings to the C library libffi, allowing C functions to be called whose types are not known before run-time.

Haskell Logo Voting has started!. Eelco Lempsink announced that voting has begun to choose the new Haskell logo. All subscribed to haskell-cafe should have received a ballot; if you are not directly subscribed, you can still send ballot requests until the end of the competition (March 24, 12:00 UTC). Make sure the message contains 'haskell logo voting ballot request' in the subject. A long discussion of what color to paint the bike shed and why this particular bike shed will not do for storing bikes ensued.

The Monad.Reader (13). Wouter Swierstra announced that a new issue of The Monad.Reader, a quarterly magazine about functional programming, is now available. Issue 13 consists of the following four articles: "Rapid Prototyping in TEX" by Stephen Hicks; "The Typeclassopedia" by Brent Yorgey; a Real World Haskell book review by Chris Eidhof and Eelco Lempsink; and "Calculating Monads with Category Theory" by Derek Elkins.

dzen-utils 0.1. Felipe Lessa announced the release of dzen-utils 0.1, which contains various utilities for creating dzen input strings in a type-safe way using some combinators, including the ability to apply colors locally (instead of applying for everything beyond some point). It can also emulate dbar and gdbar, do automatic padding, and more.


transformers versus mtl. Ganesh Sittampalam began a discussion on the relative status of the 'transformers' and 'mtl' packages.

least fixed points above something. Jens Blanck asked about a function to compute fixed points starting from a seed value (as opposed to computing the least defined fixed point).

Type equality proof. Martijn van Steenbergen requested feedback on a proposed module collecting utilities for working with type equality proofs.

What unsafeInterleaveIO is unsafe. Yusaku Hashimoto began a discussion by asking why unsafeInterleaveIO is considered unsafe, or under what circumstances its use can be considered safe.


How do students learn Haskell? Postgraduate project at University of Kent. S.J.Thompson announced that funding is available for a postgraduate project to study how students learn Haskell, based on the wealth of data collected through the instrumented version of the Helium system for Haskell. The project will be supervised by Simon Thompson and Sally Fincher, in collaboration with Jurriaan Hage, Utrecht University.

Blog noise

Haskell news from the blogosphere.

Quotes of the Week

About the Haskell Weekly News

New editions are posted to the Haskell mailing list as well as to the Haskell Sequence and Planet Haskell. RSS is also available, and headlines appear on haskell.org.

To help create new editions of this newsletter, please see the information on how to contribute. Send stories to byorgey at cis dot upenn dot edu. The darcs repository is available at darcs get http://code.haskell.org/~byorgey/code/hwn/ .