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This is a tutorial for the Haskell web framework Fn. It's designed to give web developers an idea of how Haskell web development works. It won't teach you everything you need to know, but I hope it'll give you a place to start and an idea of just how fun it is!

To get started, you need to know how to use git and some command line basics.

You also want to know a little Haskell:

  • What are types and functions in Haskell?
  • How do you define a data type?
  • How do you make a data type an instance of a type class?
  • What the Maybe type?
  • How do you do stuff "in IO"?

Learn you a Haskell is one way to learn these basics, and it's free online! You can also try the Haskell wikibook.

When you're ready to get started, clone this repository:

git clone

You'll also need to install Stack, which installs the Haskell compiler and all the libraries and modules you'll need. Just follow the directions for your operating system here.

Make sure "~/.local/bin" is in your $PATH, so your OS can find everything Stack installs.

Then change to the fntutorial directory, and run stack build. This will download and install everything! It will take a very long time if you haven't used Stack before. Be patient. Have some tea/coffee/beverage of choice.

(If you have any problems building, let me know so I can help!)

Once the build is finished, run stack exec site1 and visit localhost:3000 to see a "Hello world" Haskell site running on your machine! Type CTRL-C to quit the server when you're done.

Each site's source code contains a part of the tutorial. Read each "*.lhs" file's source to learn how to make Haskell sites with Fn, WAI, and Warp!

  • "Site1.lhs" - stack exec site1 -- a "Hello world!" site
  • "Site2.lhs" - stack exec site2 -- how do routes and handlers work?
  • "Site3.lhs" - stack exec site3 -- using Lucid for HTML responses

Start the tutorial!