Passing lambdas to functions in Kotlin - Mini Project: Build & Apply

Passing lambdas to functions

📖 Scenario: Imagine you are building a simple calculator app that can perform different operations on numbers. You want to write a function that takes two numbers and a small piece of code (a lambda) that tells it what operation to do.

🎯 Goal: You will create a function that accepts two numbers and a lambda function to perform an operation on these numbers. Then, you will call this function with different lambdas to see different results.

📋 What You'll Learn

Create a function called calculate that takes two Int parameters named a and b, and a lambda parameter named operation of type (Int, Int) -> Int.

Create a variable called add that holds a lambda to add two numbers.

Create a variable called multiply that holds a lambda to multiply two numbers.

Call the calculate function with add and multiply lambdas and print the results.

💡 Why This Matters

🌍 Real World

Passing lambdas to functions is common in apps to customize behavior, like sorting lists or handling user actions.

💼 Career

Understanding lambdas and higher-order functions is important for Kotlin developers working on Android apps or backend services.

1

Create the calculate function

Write a function called calculate that takes two Int parameters named a and b, and a lambda parameter named operation of type (Int, Int) -> Int. The function should return the result of calling operation(a, b).

Kotlin

// Write the calculate function here

Need a hint?

Remember, the lambda parameter operation takes two Ints and returns an Int. Use it inside the function to get the result.

2

Create lambdas for addition and multiplication

Create a variable called add that holds a lambda to add two Int numbers. Also create a variable called multiply that holds a lambda to multiply two Int numbers.

Kotlin

fun calculate(a: Int, b: Int, operation: (Int, Int) -> Int): Int {
    return operation(a, b)
}

// Create add and multiply lambdas here

Need a hint?

Use the syntax { x, y -> x + y } to create a lambda that adds two numbers.

3

Call calculate with lambdas

Call the calculate function with arguments 5 and 3 using the add lambda, and store the result in a variable called sumResult. Then call calculate with the same numbers using the multiply lambda, and store the result in a variable called productResult.

Kotlin

fun calculate(a: Int, b: Int, operation: (Int, Int) -> Int): Int {
    return operation(a, b)
}

val add: (Int, Int) -> Int = { x, y -> x + y }
val multiply: (Int, Int) -> Int = { x, y -> x * y }

// Call calculate with add and multiply lambdas and save results

Need a hint?

Call calculate with 5, 3, and the lambda variable like add.

4

Print the results

Print the values of sumResult and productResult on separate lines using println.

Kotlin

fun calculate(a: Int, b: Int, operation: (Int, Int) -> Int): Int {
    return operation(a, b)
}

val add: (Int, Int) -> Int = { x, y -> x + y }
val multiply: (Int, Int) -> Int = { x, y -> x * y }

val sumResult = calculate(5, 3, add)
val productResult = calculate(5, 3, multiply)

// Print sumResult and productResult

Need a hint?

Use println(sumResult) and println(productResult) to show the results.