Haskell Links

Haskell Beginners

Installing GHCi:

• The easiest way to install GHCi on OS X and Windows is using the Haskell platform packages.
  
• On Linux, we recommend to use GHC packages provided by your distribution or the binary packages provided on the GHC hompage.
  

Using GHCi:

• Official Website, User's Guide, and Tutorial
  
• Good text editors: Notepad++ (Windows), Kate (Linux with KDE desktop), gedit (Linux with GNOME desktop), jEdit (cross platform), vim (cross platform), and emacs (cross platform with good haskell-mode)
  

Learning Haskell:

• A style guide for writing Haskell code
• Hoogle: search the Haskell libraries by name and/or type
• The Haskell Prelude (Hugs version):
  • Syntax highlighted version
  • Postscript file ideal for printing
  • Commented version (note that the source code of this version is slightly different from the Hugs version, as it is optimized for speed).
• Official website of Graham Huttons "Programming in Haskell" (includes public slides)
• The official (revised) Haskell98 report defining the syntax and an informal abstract semantics for Haskell
• Free online version of the excellent book Real World Haskell
• learn how to do IO (Input/Output)
  
• understand Monads

Haskell Programmers

Using the Glasgow Haskell Compiler (GHC)

As soon as you develop some real applications, you'll need a good build environment and the speed of a compiled executable. The first is given the the Common Architecture for Building Applications and Libraries (cabal). The later is given by the Glasgow Haskell Compiler (GHC), whose interactive shell GHCi you are already using. (See for a comparison of its speed to compilers for other languages.) Apart from GHCi, GHC also supports various extensions to the Haskell language and features an integrated debugger.

• The GHCi debugger
  
• Tutorial for the debugger
• support for Concurrent Haskell including Software Transactional Memory and a prototype of Data Parallel Haskell.

Do not reinvent the wheel - Know the libraries

There exists a fast growing repository of Haskell libraries that will serve you very well during your daily programming excursions. They are all developed collaboratively on Hackage go and check them out. A few that you should definitively have a look at are:

• Gtk2hs - Haskell bindings for the cross-platform GTK gui toolkit
• HOpenGL - OpenGL bindings for Haskell (distributed with the Haskell platform)
  
• Finger Trees - "The Swiss Army Knife of Data-Structures"

Cool Applications - Haskell in "The Real World"

For a long time, Haskell and other functional languages like OCaml or
SML have been a research only programming languages. However this is no longer the case: There are companies like Galois Inc., Bluespec,
Credit Suisse and quite a few more that are using functional languages like Haskell to solve their real world problems. See the book
"Real World Haskell" (online) for explanations on how to do this best.

Furthermore, there are also a number of exciting open-source project being developed using Haskell. Most notably there are:

• darcs version control system
  
• xmonad window manager
  
• happstack a Haskell web application server
  
• yi text editor fully scriptable using dynamically loaded Haskell plugins
• hmp3 curses based mp3 player
  
• and many more
  

All of these projects are open for contributions, not to forget that there surely are
plenty of ideas you have that could possibly be realised using Haskell...

Haskell Community: Blogs & Facts

Haskell has attracted a very active and friendly community. They use the following communication channels

• IRC #haskell @ code.freenode.net
• Haskell Announcements, Haskell Cafe, mailing lists
• various blogs: a good aggregate is http://planet.haskell.org

Some interesting blogs (posts) are:

• Lambda the Ultimate Programming Languages Weblog
• Don Stewart's blog: http://cgi.cse.unsw.edu.au/~dons/blog
• Epic Games programmer Tim Sweeny at POPL'05 about the next mainstream programming language

Haskell Experts

There is a lot of active research going on with respect to functional languages and more correct and more productive programming in general. A very good starting point to delve into these topics is Oleg Kiselyov's homepage. For a starting point with respect to the implementation of functional languages see Simon Peyton Jones homepage. A few topics you might want to investigate

• learn about category theory
  • good and free lecture notes are the Category Theory Lecture Notes
    
  • An in-depth explanation of the relation between Haskell's IO system and category theoretic monads is "The Haskell Programmers Guide to the IO Monad - Don't Panic"
• learn about type level programming
  
  • statically checking correct usage of physical units (see this blog post and this library)
• learn about dependent types and
  • lightweight dependent-type programming, i.e., using Haskell's type system to preserve invariants like no out of bounds array access statically)
  • proving software correct using the calculus of constructions in Coq
  • proving software correct using Higher Order Logic in Isabelle/HOL

    (cf. the homepage of the previous Isabelle course at ETH)
    

• learn about the relation between Haskell and object oriented software construction: OOHaskell