[andrewflnr]

Am I correct in guessing, though, that it would only work for relatively sophisticated assignments that can be done in lots of different ways? Or is there always enough variety in different people's structure to tell when things are being copied?

[RBerenguel]

It was more like a quick way to check without having to remember 90 assignments. Visual inspection was far, far better (almost like a game of match 2). I taught numerical analysis, and usually there was more than one way to structure the code, in fact most assignments were clearly very different. You'd be surprised how many ways our students found to write the same Gauss inversion algorithm, for example (my personal experience is that I write always the exact same code with very minor variations, but of course I alwas refer to Golub-Van Loan for the pseudocode...) Other assignments were harder to check, there are not that many ways to write a Runge-Kutta integrator with variable stepsizes (it's basically a set of for statements in a precise order, except for the variable step integrator part), but the "fingerprints" pinpointed some odd stuff that could be checked manually.

Basically it was a fun project that got me a little into Lex, the kind of odd stuff I do in Saturday afternoons