Well, you could do worse than studying the code of some of these haskell games.
Some of these use FRP (functional reactive programming), which some people are working on as a pure, high-level technique for games and other things. But most are a typical haskellish mixture of effectful and pure functional code.
Bloggers with relevant content include James Hague.
Note FunGEn at the first link – though not actively maintained it is a 2D game engine with working examples.
There’s also the Clean language with it’s game library and nice screenshots.