To experiment with using Hackflight for flight control in Haskell, you'll first need to install Haskell and NASA Copilot (the “secret sauce” that allows you to compile Haskell code to a form suitable for running on a flight controller.) I was able install Copilot via:
cabal install copilot
cabal install copilot-c99
Next, follow these directions for installing Webots and flying a simulated quadcopter.
Finally, from the hackflight main directory, do the following:
cd webots/controllers/haskell
make
make run