Scala How to get sublist by index

Question

I have a List(1 ,2 ,3 ,4 ,5) and trying to get a sublist: List(3, 4) from it by the following way:

List(1 ,2 ,3 ,4 ,5).slice(this.size - 3 , this.size - 1 )

But I got an error

error: value size is not a member of object

How can I use "this" parameter in Scala just like in Java. Are there other ways to achieve the goal. Thank you so much.

Answer 1

You should first declare the list, and then refer to the list using its name list, not this:

val list = List(1 ,2 ,3 ,4 ,5)
list.slice(list.size -3, list.size -1)

If you really want to do this in one line, then use reverse, but it's not very efficient:

List(1 ,2 ,3 ,4 ,5).reverse.slice(1, 3).reverse

By the way, that code wouldn't be valid in Java either. this refers to the enclosing object, not to the list.

Answer 2

If you want last 3 or n elements, you can use takeRight(3) or takeRight(n).

Edit based on the question edit:

If you need to not take first f and last l elements then

List(1,2,3,....n).drop(f).dropRight(l) 

For your case it will be List(1,2,3,4,5).drop(2).dropRight(1)