People who are going through Project Euler to practice will never search for those and would likely forget the fine details quickly, so having the answers out there somewhere won't matter to them.  People who want to cheat at Project Euler already have plenty of ways (and besides, what would they gain?  At least from my minimal participication, it does not really look like a contest and there are no prizes).<p>On the other hand, people who want to learn Arc might be very greatful to have a good set of code out there.