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/memoise

Now, 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/memoise

Although 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:

• Lesson 1
• Lesson 2
• Lesson 3
• Lesson 4
• Lesson 5
• Lesson 6
• Lesson 7

Note: You need PostgreSQL installed for Lessons 8-11.

• Lesson 8
• Lesson 9
• Lesson 10
• Lesson 11