[shoki]

There are a couple of GCD algorithms that have better asymptotic performance than Euclid's (an old one is due to Knuth): http://www.ams.org/journals/mcom/2008-77-261/S0025-5718-07-0...

I'm surprised the author didn't implement the binary gcd, however, although it has the same big-O as Euclid: https://en.wikipedia.org/wiki/Binary_GCD_algorithm

[feliperibeiro]

I've been doing this sporadically and in my free time, just for fun, so there are a lot of fundamental things that haven't been covered there. :)

[shoki]

I do this sort of thing sporadically in my free time too... it's still good to go back and do stuff smarter when you learn better rather than accepting whatever they taught you in CS101 as the end of the story.