Named arguments for clarity in Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of function call with named arguments

What is the output of this Kotlin code using named arguments?

Kotlin

fun greet(name: String, greeting: String = "Hello") {
    println("$greeting, $name!")
}

greet(greeting = "Hi", name = "Anna")

A Hi, Anna!

B Hello, Anna!

C Hi, greeting!

D Compilation error

💡 Hint

Look at how the arguments are passed by name, not by position.

Named arguments allow you to specify parameters in any order. Here, greeting is "Hi" and name is "Anna", so the output is "Hi, Anna!".

❓ Predict Output

intermediate

Output with default and named arguments

What will this Kotlin code print?

Kotlin

fun calculate(x: Int, y: Int = 10, z: Int = 5) = x + y * z

println(calculate(z = 3, x = 2))

A Compilation error

B 17

C 32

D 15

💡 Hint

Remember the order of operations and which arguments are used.

Named arguments allow passing z=3 and x=2, y uses default 10. So calculation is 2 + 10 * 3 = 2 + 30 = 32.

🔧 Debug

advanced

Identify the error with named arguments

What error does this Kotlin code produce?

Kotlin

fun displayInfo(name: String, age: Int) {
    println("Name: $name, Age: $age")
}

displayInfo(age = 25)

A Error: No value passed for parameter 'name'

B Compilation succeeds with no output

C Prints: Name: , Age: 25

D Error: Named argument 'age' not found

💡 Hint

Check if all required parameters have values.

The function requires both 'name' and 'age'. Only 'age' is provided, so Kotlin reports missing 'name'.

📝 Syntax

advanced

Which call is syntactically correct?

Given the function below, which call is syntactically correct in Kotlin?

Kotlin

fun orderPizza(size: String, cheese: Boolean = true, pepperoni: Boolean = false) {}

// Calls:

A orderPizza(size = "Medium", pepperoni = true)

B orderPizza(cheese = false, "Large")

C orderPizza("Small", pepperoni = true, cheese = false)

D orderPizza(pepperoni = true, cheese = false, "Large")

💡 Hint

Named arguments must come after positional arguments.

In Kotlin, positional arguments must come before named arguments. Both A (all named) and C (positional first, then named) are correct. B and D have positional arguments after named arguments.

🚀 Application

expert

Determine the final map after function calls with named arguments

Consider this Kotlin function that updates a map. What is the final content of the map after these calls?

Kotlin

fun updateMap(map: MutableMap<String, Int>, key: String, value: Int = 1) {
    map[key] = map.getOrDefault(key, 0) + value
}

val myMap = mutableMapOf("a" to 2)
updateMap(map = myMap, key = "b")
updateMap(key = "a", map = myMap, value = 3)
updateMap(myMap, "b", 4)

println(myMap)

A {a=2, b=8}

B {a=3, b=5}

C {a=5, b=1}

D {a=5, b=5}

💡 Hint

Trace each call and how the map updates with default and named arguments.

Initially, map has {a=2}. First call adds b=1 (default). Second adds 3 to a (2+3=5). Third adds 4 to b (1+4=5). Final map is {a=5, b=5}.