High-Order Function

Higher order function is a function that does at least one of the following:

1. takes one or more functions as an argument.
2. returns a function as a result.

In Kotlin, functions are first-class citizens, which means that they can be assigned to variables, passed as arguments to other functions, and returned as results from functions. This makes Kotlin a functional programming language.

The ability to pass functions as arguments to other functions allow developers to create more flexible and reusable code. Developers can write functions that can accept different functions as arguments, allowing the same code to be reused with different implementations. This also allows developers to create libraries of functions that can be used by other developers without having to know the implementation details.

A good example of a higher-order function is a map that applies a given function to each element of the collection, e.g. list or set, returning the results in a collection of the same type. We will discuss this later in the post.

How Higher-Order Functions Work

To define a higher-order function in Kotlin, you need to specify a function type as a parameter, using the () -> Unit syntax. Here is an example:

fun operation(x: Int, y: Int, op: (Int, Int) -> Int): Int {
    return op(x, y)
}

In this example, the operation function takes three arguments: x and y, which are integers, and op, which is a function that takes two integer arguments and returns an integer result. The operation function then calls the op function with x and y as arguments and returns the result.

Here is an example of how to use the operation function with a lambda expression as the op argument:

val sum = operation(5, 10) { a, b -> a + b }

In this example, we are calling the operation function and passing in a lambda expression as the op argument. The lambda expression takes two integer arguments a and b, adds them together, and returns the result. The operation function then returns the result, which is the sum of 5 and 10, which is 15.

Examples of Higher-Order Functions in Kotlin

Higher-order functions are commonly used in Kotlin to create more flexible and reusable code. Here are some examples of how to use higher-order functions in Kotlin: map, filter, fold, reduce, etc.

Map Function

The map function is a higher-order function that is used to transform a collection into another collection by applying a function to each element in the collection. Here is an example of how to use the map function in Kotlin:

val numbers = listOf(1, 2, 3, 4, 5)
val squaredNumbers = numbers.map { it * it }

In this example, we are using the map function to transform a list of integers into another list of integers, where each integer is squared. The lambda expression { it * it } is the function that is applied to each element in the list.

Conclusion

In conclusion, higher-order functions are a powerful feature of Kotlin that allows functions to be treated as values, which enables more flexible and reusable code. By using higher-order functions, you can create custom control structures and encapsulate common functionality into reusable functions. Higher-order functions are commonly used in functional programming paradigms and can be particularly useful when working with collections of data.

Please let me know your suggestions and comments. Follow for more such easy and helpful tutorials.

Thanks for reading…

Happy Coding!