I haven't been using the debugger, partly because I'm not all that familiar with Eclipse and partly because I suspected it would work the way you say with all those recursive calls anyway. I've been using Scala worksheets a fair bit for building up the elements of my solutions, and of course using the unit tests to see if things are working. I've noticed we need to implement extra tests to check the various edge cases these days.
I wonder how far people are really using this kind of recursion in real-world projects, especially where people are still in the process of learning FP e.g. moving from a standard
Java platform. So you might start out with a fairly imperative solution to get the inputs/outputs working right, then re-factor that into a more elegant recursive approach where appropriate. And some of the recursive solutions we've been working on here are not especially efficient, so recursion isn't always the best approach anyway. Even if it feels really cool to get something like this working recursively!