No built-in is needed for an efficient reverse. It's just one or two lines longer because you need to write a tail-recursive helper with an accumulator, same as

No built-in is needed for an efficient reverse. It's just one or two lines longer because you need to write a tail-recursive helper with an accumulator, same as in functional languages: https://stackoverflow.com/a/74777180 https://stackoverflow.com/a/74777180