IMO A major mistake books make is immediately attempting to visualize the call stack. This is important to be able to do. However, practitioners will simply ima

IMO A major mistake books make is immediately attempting to visualize the call stack. This is important to be able to do. However, practitioners will simply imagine the code working on an arbitrary element and somewhat ignore the call stack (except perhaps for debugging). I disagree that factorial is not "applied" enough -- no matter what problem you choose, it will be interesting to some students and not others. The entire purpose of recursion is not speed, but to more aptly fit your mental model -- resulting in simpler code. In that light, I am also surprised that the article did not explain that recursion is essentially solving a problem in terms of a simpler problem, e.g. n! = n*(n-1)!, which eventually becomes the trivial case 0! = 1.