Replace element in List with scala

Question

How do you replace an element by index with an immutable List.

E.g.

val list = 1 :: 2 ::3 :: 4 :: List()

list.replace(2, 5)

Answer 1

If you want to replace index 2, then

list.updated(2,5)    // Gives 1 :: 2 :: 5 :: 4 :: Nil

If you want to find every place where there's a 2 and put a 5 in instead,

list.map { case 2 => 5; case x => x }  // 1 :: 5 :: 3 :: 4 :: Nil

In both cases, you're not really "replacing", you're returning a new list that has a different element(s) at that (those) position(s).