Kotlin High Order function Composition

As we all know that in Kotlin, we can pass a function as a parameter in the function. In Kotlin, we are using high order functions in order to implement the business logic and get the result.

Syntex:-

var lambda = {println("Hello, this is my function.") }
      // higher-order function 
fun higherfunc( lmbd: () -> Unit ) {     // accepting lambda as parameter
    lmbd()                               //invokes lambda expression
}
fun main(args: Array<String>) {
     //invoke higher-order function
    higherfunc(lambda)                 // passing lambda as parameter
}

var lambda = {println("Hello, this is my function.") }

// higher-order function

fun higherfunc( lmbd: () -> Unit ) { // accepting lambda as parameter

lmbd() //invokes lambda expression

}

fun main(args: Array<String>) {

//invoke higher-order function

higherfunc(lambda) // passing lambda as parameter

}

In kotlin, we can combine two methods and get the result as Lambdas are a further level of abstraction which give you the opportunity to make behavior variables, you still have to provide them with data. We can Achieve it using the Extention function.

Let see the composition of two methods in Kotlin:-

// Extension function on lambda
private infix fun ((Int, Int) -> Int).plus(f: (Int, Int) -> Int) = {
    p1: Int, p2: Int, p3: Int, p4: Int -> this(p1, p2) + f(p3, p4)
}

// Usage
val func1: (Int, Int) -> Int = { a, b -> a + b }
val func2: (Int, Int) -> Int = { a, b -> a * b }

// first two parameters (1 and 2) for the `first` lambda, 
// second two parameters (4 and 3) for the `second` lambda
val sum = (first plus second)(1, 2, 4, 3) // result is 15

// Extension function on lambda

private infix fun ((Int, Int) -> Int).plus(f: (Int, Int) -> Int) = {

p1: Int, p2: Int, p3: Int, p4: Int -> this(p1, p2) + f(p3, p4)

}

// Usage

val func1: (Int, Int) -> Int = { a, b -> a + b }

val func2: (Int, Int) -> Int = { a, b -> a * b }

// first two parameters (1 and 2) for the `first` lambda,

// second two parameters (4 and 3) for the `second` lambda

val sum = (first plus second)(1, 2, 4, 3) // result is 15

We can see the output on the console:-

In order to get more details, You can go through the following link:-

https://kotlinlang.org/docs/reference/extensions.html

https://kotlinlang.org/docs/reference/lambdas.html

piyush pandey 31 January 2021

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Kotlin High Order function Composition

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