It seems like the author has realised that there are a few common functional programming patterns (folds, maps) that are also common ways of combining information and operating on data structures, and seen the parallel to some operations that we frequently want to do within neural networks. A 'function' is simply a thing that takes another thing and produces a third thing. This doesn't seem that revolutionary or insightful - do these ideas give us any extra knowledge about neural networks or is this just a nice parallel?