[fiatjaf]

Do people really need all that text (in the textbook) to understand what a recursive function is?

[pgbovine]

Yes, recursion is an extremely challenging topic for novices. Beware of the expert blind spot, in which experts such as yourself drastically underestimate how difficult concepts are for novices to learn:

http://teaching.colostate.edu/tips/tip.cfm?tipid=181