e.g., (1..10), but also ("apple".."kiwis") or ('A'..'Z').
In this case, String#succ returns a string with the last alphanumeric character transformed into its successor, e.g., "apple".succ == "applef".
The only time I've used it is implementing the range interface; I've never called it directly, let alone to increment an integer.
I still don't see why it doesn't just use the common syntax though that does the same thing. It's intriguing that the Python one has no example for that row. Perhaps they are specifically looking for idiomatic techniques, even if they're not commonly used.
I note that the page is on a wiki so I could fix it, but given it's been there for years, I suspect there's a good reason no-one has already made the change.
The reason is that x would be referring to a number like 1, 42, or whatever, and numbers are immutable in Ruby. You can't "change" a number in-place. If you could change Ruby's concept of 1 into 2, then 1 would cease to exist and that would be a Bad Thing™ :-)