memoi.se is a complete web application written in Haskell, designed to be used as a reference by beginners. By looking at the git commit history of this repository, you can see a series of changes, building up from a simple "Hello, world!" app to a fully-functional hyperlink shortener with PostgreSQL database integration, in under 100 lines of Haskell.
Begin by entering the following commands into your terminal window. You'll need to have Haskell installed.
$ git clone git://github.com/ryantrinkle/memoise
$ cd memoise
$ git checkout lesson-1
$ cabal install
$ ./dist/build/memoise/memoiseNow, open a browser and go to http://localhost:8000/.
You should see "Hello, world!" displayed. If you look at src/Main.hs in lesson-1, you can see that this is achieved with just a few simple lines of Haskell.
To shut down the memoi.se server, press Ctrl-C in your terminal window. Once you've taken a look around in Lesson 1, you can move on to Lesson 2 by running
$ git checkout lesson-2
$ cabal install
$ ./dist/build/memoise/memoiseAlthough looking at the checked out code may be helpful, a more informative way to look at this project is by viewing the commit history. Each lesson is a single git commit, designed to add a single piece of functionality, as you might do if you were creating a website from scratch.
You can take a look at the changes made in each lession here:
Note: You need PostgreSQL installed for Lessons 8-11.