Well, I would argue that this article really is an introduction to functional programming using Haskell. Most of the concepts he/she introduce are not specific

Well, I would argue that this article really is an introduction to functional programming using Haskell. Most of the concepts he/she introduce are not specific to Haskell but are more or less specific to functional programming languages. But the author doesn't seem to be very well aware of that. Quoting the article: "Haskell is very different. The language uses a lot of concepts I had never heard about before." All that to say that if you already know some functional programming this probably isn't for you. Edit: clarity.