[m0a0t0]

It doesn't just assume knowledge of the language though. Assuming knowledge of Applicative, Monad and Functor is fine but as the current top comment says there is a lot more than that. Most of which you wouldn't find in a normal Haskell tutorial/article

[ColinWright]

No, exactly. This is not a beginner tutorial - there are plenty of those. This is for people who have already acquired some knowledge of the language. It's an intermediate article for those looking to move beyond the toy programs solving toy problems usually presented.