I'm not entirely sure if "next-to-last" and "last" can be described as opposites, though :-)

Well, there is this: Opposites are a tricky concept, not well-defined in most domains. Your implication is that the opposite of last is "first". But doesn't it make at least as much sense to say the opposite of last is "not last"? From a programing/math standpoint, it seems like a strictly better, less arbitrary definition.