Haskell Rich Web Application Example

This exercise will demonstrate how to write a Haskell back-end for a dynamic, real-time web application. We will write the client-side logic using CoffeeScript and Knockout.js and implement two-way communication with WebSockets on top of a Haskell web server.

How to get started

First, install the Haskell Platform and get the latest repository information by running

cabal update

Next, you'll need Node.js for running the Jade/CoffeeScript/Stylus tool-chain. Best way to install Node is by using NVM.

Clone the repository

git clone git://github.com/leonidas/lambda-webdev.git
cd lambda-webdev

Get the required JavaScript tools

npm install

Using cabal-dev

cabal-dev is a tool for installing packages in an isolated project environment instead of installing libraries globally. It makes it easier to avoid dependency conflicts but you have to rebuild everything you install so it takes some time to prepare a new project.

cabal install cabal-dev
cabal-dev configure
cabal-dev install-deps
cabal-dev build

You also need to modify the file grunt.coffee and set

useCabalDev   = true

at the top of the file.

Using ordinary cabal

There are some situations where cabal-dev doesn't work correctly on MacOS X so you might opt to use the regular cabal instead.

cabal configure
cabal install --only-dependencies
cabal build

Starting the server

./grunt

Editing Haskell sources

In order to get proper auto-complete and other goodies, you should install ghc-mod.

cabal install ghc-mod

The tool works with either vim, emacs or Sublime Text (via SublimeHaskell). For SublimeHaskell, you also need to run

cabal install aeson haskell-src-exts