Aggregation
sum, count, fold, reduce.
Aggregating Collections
Aggregation reduces a collection to a single value. Kotlin provides ready-made functions like sum, count, average, max, and general-purpose fold and reduce.
sum and average
sum adds up numeric elements, and average returns their mean as a Double.
fun main() {
val numbers = listOf(2, 4, 6, 8)
println("Sum: ${numbers.sum()}")
println("Average: ${numbers.average()}")
}