I wasn’t really sure of quite how to start this off. I finally decided to just dive right in with a simple function definition, and then give you a bit of a tour of how Haskell works by showing the different ways of implementing it.
Before getting to the meat of the tutorial, I thought it would be good to provide some setup
information in a distinct, easy to find place. This short post will tell you where to find
a Haskell implementation and related tools.
I’m testing my examples for these articles using two different Haskell implementations:
ghci which is included in its distribution. It’s also good to have some extra tool support for Haskell programming. A lot of editors, such as
emacs, vim, and textmate provide Haskell tooling. The best tooling that I’ve seen is the EclipseFP feature for the Eclipse programming environment. Admittedly, I’m a bit biased here;
I’ve used to lead an Eclipse-based research project, so I’m a huge Eclipse fan. But the Eclipse
Haskell support really is very nice, and it’s very easy to set up. Installing Eclipse involves
nothing more than downloading it – it runs very smoothly in-place with no setup; and installing
EclipseFP can be done inside of Eclipse using the update manager – there’s a complete step by step
explanation at the EclipseFP homepage linked above.
If you’re a visual studio user, there’s a Haskell package called Visual Haskell. I’ve never used it (I’m not
a windows guy; I use MacOS and Linux.), but I’ve heard quite good things about it.
If you prefer just using a simple text editor, vim includes the Haskell package; for emacs, you
can get a Haskell mode here. For TextMate, you can get
the Haskell bundle via the normal bundle installation route.
For understanding the execution of Haskell programs, particularly when the laziness gets a bit
confusing, being able to generate an execution trace can be a huge help. There’s a tool called Hat which can generate very nice, easy to follow traces for
GHC programs.
You can write fancy documentation for Haskell programs using a tool called Haddock. Haddock is something like Javadoc for
Haskell. It piggybacks on a “literate” syntax mode built-in to both GHC and Hugs, so
at least primitive support for Haddock is included in all of the Haskell tools; many also
provide additional Haddock support.
The capital of the online Haskell world is the Haskell.org site. It has links to numerous other tutorials, the language spec, implementations, events, etc.
There’s a Haskell blog called The Complete Sequence, which includes a weekly Haskell news update, as well as other interesting articles and links. There’s another Haskell blog called Planet Haskell which also has some good material.
Before diving in and starting to explain Haskell, I thought it would be good to take a moment and answer the most important question before we start:
**Why should you want to learn Haskell?**
It’s always surprised me how many people *don’t* ask questions like that.
Haskell is a valuable language for a lot of different reasons, but the most important one is that *it
changes the way that you think about programming*. Haskell does things in a very different way from the imperative languages that most of us are familiar with. And it’s an extremely well-designed language, so there isn’t a ton of crap standing between you and the concepts that you can learn from it.