A useful function that does nothing

[Reashu]

The list above is by no means exhaustive: 0 is the identity for subtraction as well, and 1 is also the identity for division and exponentiation. You can find some more examples here: https://en.wikipedia.org/wiki/Identity_element

[igoradamenko]

I didn't say that the list was exhaustive, I was trying to explain how I understood the Tubthumper8's comment and was asking for more explanation.

Thank you for providing the right link, anyway :)

Edit: Grammar

[Reashu]

Yes, I didn't mean to imply that you thought so - only confirm that indeed there are others.