The original purpose of this program was to show CS15 students what actual working code looks like. The emphasis was on having a good, extensible design which the students could see in practice. The code was handed out to students and gone over in section with me, their TA. Overall reaction was that it was very good to see a whole program and not several unrelated pieces. Proper placement of this helper programwould be after the students have finished Swarm, or the equivalent program.
Here we reuse and extend this example to show how a program is created from the very first moment a student begins to think about it.