Here's a curiosity:

Do you know a game that was completely written in a functional programming language like Haskell or Lisp? Are there any graphical libraries for them, or anything where someone could write a game with? If there are, how advanced they are? Are there engines? OpenGL support? I've played with haskell a bit and just found it incredibly interesting, and I would like to know your opinion about the subject.

Here's something interesting that I've found: Game Oriented Assembly Lisp (or GOAL).

Another interesting link (Haskell): http://www.haskell.org/haskellwiki/Game_Development

I think John Carmack implemented Wolfenstein3D in Haskell a while ago, don't think he released the sources though. You could try to look it up in his twitter account.

I just saw his tweet now. Wolfenstein3D on Haskell? That's insane :). But coming from him, I'm not surprised with it.

Land of Lisp and Realm of Rackett are books that teach lisp by making games. They both finish by creating grapical browser based multiplayer games.