Hands-On Object-Oriented Programming with Kotlin

The reduce function

To understand the concept of the reduce function, we'll use addition as an operation. The reduce function adds all elements in the list and returns a result. The difference between the fold and reduce function is that the fold function provides an initial value, fold(0){i,j -> i + j}, but the reduce function does not, reduce { acc, i -> i + acc}.

The reduce function takes a lambda expression that takes two variables and returns a result, as follows:

var numbers = listOf<Int>(1,2,3,4,5)var result = numbers.reduce { acc, i ->  i + acc}println("From beginning : add all elements of the list $result")

The reduce function has two different variants.