Using TeX to control a Mars rover (see page 5)
haskell.org
haskell.org
TeX is an enjoyable language for programming--it's something like writing in lambda calculus. It's too bad most people don't realize it's a complete language. I use it all the time for generating automated documents and such.
Is it a joke, is he really serious about this?
In this case "controlling a rover" was the task of the 2008 ICFP programming contest, and he thought it would be "interesting" to write an entry using TeX. While he wasn't the highest scoring entry, he won the judges' prize for his unusual approach.
A more practical explanation of the project, from his blog: http://sdh33b.blogspot.com/2008/07/icfp-contest-2008.html