The scheme way is also the ruby way, so it's probably the most conventional. I could see us using join/d though, as it looks kinda like the w/link method in the arc challenge, so we could be starting our own convention. Personally, I'd love to see a convention for predicates to end in '?', which would go along with the '!' convention quite well.
Except that the ruby way isn't consistent. ! is used to warn people that this method is destructive for sure. The lack of ! doesn't imply non-destructiveness.
