Yes, it assumes some knowledge of the language. But imagine if every article about, say, Ruby, had to explain things in a way that someone who'd only ever seen C would understand? Authors would be hamstrung, unable to talk about things at any level other than the most elementary.
If you're going to talk about the power of a language you have to allow the use of language that talks about that power. To talk about what you can do in Haskell beyond toy problems you need to allow people to use more than just toy language.
If readers aren't willing to do any work, its tough to help them learn anything new.
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
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.
Author here: the concept of `Applicative`s is unique to Haskell and has no parallel in other programming languages. This makes the post difficult to write to a broad audience. Instead, I just tried to show the neat things you could do with `Applicative`s to try to entice people to learn more about them.
