Welcome to issue 58 of HWN, a weekly newsletter covering developments in the Haskell community.


New Book - Programming in Haskell. Graham Hutton announced a new Haskell textbook: Programming in Haskell. This introduction is ideal for beginner programmers: it requires no previous programming experience and all concepts are explained from first principles via carefully chosen examples. Each chapter includes exercises that range from the straightforward to extended projects, plus suggestions for further reading on more advanced topics. The presentation is clear and simple, and benefits from having been refined and class-tested over several years.

Gtk2Hs version 0.9.11. Duncan Coutts announced Gtk2Hs - a GUI Library for Haskell based on Gtk+, version 0.9.11, is now available. Gtk2Hs features: automatic memory management; Unicode support; nearly full coverage of Gtk+ 2.8 API; support for several additional Gtk+/Gnome modules (Glade visual GUI builder, cairo vector graphics, SVG rendering, OpenGL extension and more).

cabal-make version 0.1. Conal Elliott announced Cabal-make, a GNU make include file to be used with Cabal in creating and sharing Haskell packages. A few highlights: web-based, cross-package links in Haddock docs; syntax coloring via hscolour, with per-project CSS; links from the Haddock docs to hscolour'd code and to wiki-based user comment pages. It is available here.

Vty 3.0.0. Stefan O'Rear announced a new major of vty, featuring improved performance. vty is notably used in yi to provide a terminal interface supporting syntax highlighting.

Haskell Xcode Plugin. Lyndon Tremblay announced the first release of a plugin for Xcode enabling Haskell syntax highlighting, Xcode projects compiling and linking, and a couple missing features, for Haskell (GHC).

urlcheck 0.1: parallel link checker. Don Stewart announced the first release of urlcheck, an parallel link checker, written in Haskell. Frustrated with the resources and time consumed by 'linkchecker', urlcheck is a lightweight, smp-capable replacement in Haskell. urlcheck pings urls found in the input file, checking they aren't 404s. It uses Haskell threads to run queries concurrently, and can transparently utilise multiple cores if you have them.

The Monad.Reader: call for copy. Wouter Swierstra welcomed articles for the next issue of The Monad.Reader. Submit articles for the next issue by e-mail before April 13th, 2007. Articles should be written according to the guidelines available from The Monad Reader home.

TV-0.2 and GuiTV-0.2. Conal Elliott announced TV, a library for composing tangible values ('TVs'), values that carry along external interfaces. In particular, TVs can be composed to create new TVs, and they can be directly executed with various kinds of interfaces. Values and interfaces are combined for direct use, and separable for composition. GuiTV adds graphical user interfaces to the TV (tangible value) framework, using Phooey. The functionality was part of TV up to version 0.1.1, and is now moved out to a new package to eliminate the dependency of core TV on Phooey and hence on wxHaskell, as the latter can be difficult to install.

Haskell-mode 2.2. Stefan Monnier released version 2.2 of the Haskell-mode package for Emacs. It has very few visible changes, mostly some commands to query an underlying interactive hugs/ghci in order to get type/info about specific identifiers.

Data.CompactString 0.1. Twan van Laarhoven announced a beta Unicode version of Data.ByteString. The library uses a variable length encoding (1 to 3 bytes) of Chars into Word8s, which are then stored in a ByteString.

HSXML version 1.13. Oleg Kiselyov announced version 1.13 of HSXML. HSXML is a library for writing and transforming typed semi-structured data in Haskell -- in S-expression syntax, with the extensible set of `tags', and statically enforced content model restrictions. A particular application is writing web pages in Haskell. We obtain HTML, XHTML or other output formats by running the Haskell web page in an appropriate rendering monad. The benefit of representing XML-like documents as a typed data structure/Haskell code is static rejection of bad documents -- not only those with undeclared tags but also those where elements appear in wrong contexts.

Haskell XML Toolbox 7.1. Uwe Schmidt announced a new version of the Haskell XML Toolbox. The main change is the step from cvs to darcs. The documentation has source links into the darcs repository. A tutorial is available in the Haskell wiki.

OmegaGB, Haskell Game Boy Emulator. Bit Connor announced OmegaGB, an emulator for the Nintendo Game Boy, written in pure Haskell. It uses gtk2hs for the user interface, but there is also a version that doesn't require gtk2hs and uses ascii art. You can find more information about the program at the website.

Takusen 0.6. Oleg and Alistair announced a new release of Takusen, the database library for Haskell. There are a large number of changes and bug-fixes in this release, including improved Oracle and PostgreSQL support.

hoogle.el. David House announced Hoogle.el, a simple Emacs Lisp library that nicely integrates Hoogle into Emacs.

Buggy nofib. Josep Silva Galiana announced a 'buggy' version of the nofib collection of Haskell programs. All programs contain one of these bugs: a bug that produces an incorrect result; a bug that produces non-termination; a bug that produces an exception (e.g., div by zero). The buggy nofib suite can be used to test debugging tools.

nobench: Haskell implementation shootout. Don Stewart announced nobench, a cross-implementation performance benchmark suite, based on nofib, comparing the performance of various Haskell compilers and bytecode interpreters on a range of programs.

Derangement version 0.1.0. Dennis Griffith announced the initial version of derangement, a library for finding a derangement of a set. A derangement of a set is a permutation with no fixed points, like many constrained matching problems it is susceptible to solution via a Max-flow algorithm.

HSH 1.0.0. John Goerzen announced the first release of HSH. HSH is designed to let you mix and match shell expressions with Haskell programs. With HSH, it is possible to easily run shell commands, capture their output or provide their input, and pipe them to/from other shell commands and arbitrary Haskell functions at will. HSH makes it easy to run shell commands. But its real power is in piping. You can pipe -- arbitrarily -- between external programs, pure Haskell functions, and Haskell IO functions

A new Haskell cookbook. Martin Bishop began a preliminary page, and fleshed out some of the headers/sub-headers on the wiki page for a good Haskell Cookbook (not a PLEAC clone). Please contribute.


This section covers the Haskell' standardisation process.


This week's proposals and extensions to the standard libraries.


Haskell with only one typeclass. Oleg Kiselyov described how, if the ability to define typeclasses is removed from Haskell, no expressivity is lost. If Haskell had only one, pre-defined typeclass with only one method, we could still do normal Haskell programming with standard and user-defined overloaded numerical functions, monads, monad transformers, etc. Haskell with only one typeclass can express all of Haskell98 typeclass programming idioms including constructor classes, plus multi-parameter type classes and some functional dependencies.

Data type declarations are implicitly moduled. Chris Moline proposed an idea to allow multiple data declarations to share constructors by having them be implicitly declared inside a module.

Importance of MonadRandom. Yitzchak Gale pointed out the importance of Cale Gibbard's MonadRandom. This monad makes it possible to write functions that use randomness without having to specify in advance whether the source of randomness will be a pure pseudorandom number generator, as in System.Random, or physical randomness via the IO monad, such as your operating system's source of physical randomness, or random.org, or a hardware random generator.

Become a GHC build slave!. Simon Marlow pointed out that, thanks largely to Ian Lynagh, GHC now has a BuildBot infrastructure to automate nightly builds on multiple platforms. This replaces the old set of shell scripts that we used to run nightly builds; now adding new clients to the setup is relatively easy. So far we have various Windows builds running, and I'll be moving over the existing Linux nightly builds in due course.

Editor support for low level hacking. Don Stewart mentioned some tools used for making low level optimisation of GHC Haskell code easier

Optimisation fun. Creighton Hogg sparked a long thread on optimising prime sieves in Haskell

OO Design in Haskell Example. Steve Downey began a thread on OO design in Haskell

Safe lists with GADTs. Neil Mitchell explored a safe version of head and tail, on a safe version of lists, using GADTs


Research position at Nokia Research Center. Jamey Hicks announced the availability of a senior research engineer position at Nokia Research Center Cambridge, US. They are seeking an exceptional, highly motivated individual who is interested in a unique opportunity to collaborate with a world-class academic research community. This position is for the Armo project at NRC Cambridge, using Bluespec hardware description language to radically improve Nokia's ability to develop advanced SOCs and corresponding software for future mobile phones and mobile computers. We are investigating co-development of hardware and software components for such devices. Success in the project will lead to both academic publication as well as a significant positive impact on Nokia products and engineering.

New PhD Positions Computing Science, Chalmers University. Koen Claessen announced new PhD positions for 2007, at Chalmers University of Technology. The focus is on algorithms, bioinformatics, distributed systems and computing, functional programming, formal methods, interaction design, language technology, language based security, parallel and high performance computing, programming logic and type theory, but research is not restricted to these topics.

Positions at Oxford: refactoring tools. Oege.de.Moor announced the availability of positions in the Programming Tools Group at Oxford, researching aspect refactoring tools

Blog noise

Haskell news from the blogosphere.

Quotes of the Week

Code Watch

Wed Feb 28 05:07:14 PST 2007. Simon Marlow. Remove vectored returns. We recently discovered that they aren't a win any more, and just cost code size.

Wed Feb 21 09:04:01 PST 2007. simonpj. Allow GADT syntax for newtypes

About the Haskell Weekly News

Each week, 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. Headlines are available as PDF.

To help create new editions of this newsletter, please see the contributing information. Send stories to dons at cse.unsw.edu.au. The darcs repository is available at darcs get http://www.cse.unsw.edu.au/~dons/code/hwn