Does not work properly when a negative number is given

You could also do (0...number) instead of (1...number)

Interesting! I was not aware of the range syntax with 3 dots, where 1...n exludes the end of the range.

O my love. So beautiful

short and pithy，easy to read

last is O(n) anyway, so whether that's in reverse or in something else doesn't really matter.

(If I'm wrong, please call me on it.)

lol forget that already its self xD

I am of the same opinion :)

I believe that without self it would not know what iterable object it was iterating over.

So without specifying 'self' it just forwards it to the existing upcase method?

The entire list is not reversed due to laziness. Unfortunately, I cannot assess to what extent the optimizer discards the overhead...