Map doesn't mutate, it returns the result of applying a function to the (possibly immutable) value. I believe you can also, say, `select icolumn * 2 from table`

Map doesn't mutate, it returns the result of applying a function to the (possibly immutable) value. I believe you can also, say, `select icolumn * 2 from table`, where `icolumn * 2` provides precisely the same functionality as the function passed to a map.