filter

filter function enables you to filter collections. It takes a filter predicate as a lambda-parameter. The predicate is applied to each element. Elements that make the predicate true are returned in the result collection.

fun main() {

    val numbers = listOf(1, -2, 3, -4, 5, -6)      // 1
    
    val positives = numbers.filter { x -> x > 0 }  // 2
    
    val negatives = numbers.filter { it < 0 }      // 3

    println("Numbers: $numbers")
    println("Positive Numbers: $positives")
    println("Negative Numbers: $negatives")
}

1. Defines collection of numbers.
2. Gets positive numbers.
3. Uses the shorter it notation to get negative numbers.