Functional paradigms

Kotlin supports a functional style of programming that allows you to write more elegant, concise, and expressive code.

In Kotlin, we don't have to write lengthy code to provide simple functionality. Pure functions and higher-order functions avoid mutating the states, thereby reducing the complexity of the code and improving its readability.

Lambda expressions are anonymous functions that represent the implementation of a Single Abstract Method(SAM) interface. We can pass lambda expressions to functions. In doing this, we are not passing objects, but instead we are passing behaviors to the functions that are evaluated without mutating the state of an object. This turns a function into a higher-order function.

Consider the following lambda expression:

val greetingLambda = { println("Greet from inline lambda") }

This can be invoked using the following:

greetingLambda() or

greetingLambda.invoke()

The output of the preceding lambda expression is as follows:

Let's write an inline lambda expression to print even numbers:

listOf(0,1,2,3,4,5,6,7,8,9)
.filter{ e -> e % 2 == 0}
.forEach{ e -> println(e)}

The output will be as follows: