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That's a little bit unfair though. If you pushed an infinite number of
object of whatever class, you'd eventually run out of memory.

I personally find #first() rather confusing (BTW [1,2,3].first
(3).class => Array). I'd rather prefer [0..4] (although [0,5] should
perform slightly better) or maybe #each_index, which doesn't create an
intermediary array. #each_index would also have the advantage that it
expects only an Enumerable.