Map & Filter

Map & Filter

map transforms each element; filter keeps only matching elements:

val nums = List(1, 2, 3, 4, 5, 6)
val evens = nums.filter(x => x % 2 == 0)
println(evens)  // List(2, 4, 6)

val doubled = nums.map(x => x * 2)
println(doubled)  // List(2, 4, 6, 8, 10, 12)

Chaining

val result = nums.filter(x => x % 2 == 0).map(x => x * x)
println(result)  // List(4, 16, 36)

Your Task

Write a function doubleEvens that takes a List[Int] and returns a new list containing only the even numbers, each doubled.