What I find interesting is that I actually don't mind the single letters at all. As others have said, a name is a name and I don't find either "substitution" o

What I find interesting is that I actually don't mind the single letters at all. As others have said, a name is a name and I don't find either "substitution" or "ap" any more enlightening than "S". I also find that the currying of the parameters in the JS code is hard to read. As soon as I see the type signatures in the next chart, though, it becomes obvious what it's doing.