Function declaration syntax in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a function named greet.

Kotlin

fun [1]() {
    println("Hello!")
}

Drag options to blanks, or click blank then click option'

AsayHello

BprintMessage

Chello

Dgreet

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different function name than requested.

Forgetting to write the function name after fun.

The function name should be greet as specified.

2fill in blank

medium

Complete the code to declare a function that returns an Int value 5.

Kotlin

fun getNumber(): [1] {
    return 5
}

Drag options to blanks, or click blank then click option'

AString

BDouble

CInt

DBoolean

Attempts:

3 left

💡 Hint

Common Mistakes

Using String or other types instead of Int.

Omitting the return type when the function returns a value.

The function returns an integer, so the return type should be Int.

3fill in blank

hard

Fix the error in the function declaration to accept a String parameter named name.

Kotlin

fun greet([1]: String) {
    println("Hello, $name!")
}

Drag options to blanks, or click blank then click option'

Agreeting

Bname

CName

Dmessage

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different parameter name than used inside the function.

Capitalizing the parameter name incorrectly.

The parameter name should be name to match the usage inside the function.

4fill in blank

hard

Fill both blanks to declare a function that takes two Int parameters and returns their sum.

Kotlin

fun add([1]: Int, [2]: Int): Int {
    return a + b
}

Drag options to blanks, or click blank then click option'

Aa

Bx

Cb

Dy

Attempts:

3 left

💡 Hint

Common Mistakes

Using parameter names that don't match the return statement.

Swapping the order of parameters.

The parameters should be named a and b to match the return statement.

5fill in blank

hard

Fill all three blanks to declare a function that returns a greeting message with the given name.

Kotlin

fun greet([1]: String): [2] {
    return "Hello, " + [3]
}

Drag options to blanks, or click blank then click option'

Aname

BString

DInt

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong parameter or return types.

Using a different variable name than the parameter.

The function takes a parameter name of type String and returns a String greeting using name.

Practice

1. Which of the following is the correct way to declare a simple function named greet in Kotlin that takes no parameters and returns no value?

easy

A. function greet() { println("Hello") }

B. fun greet() { println("Hello") }

C. def greet() { println("Hello") }

D. fun greet { println("Hello") }

Solution

1. Step 1: Identify the correct keyword for function declaration

   Kotlin uses the keyword fun to declare functions. Options using function or def are incorrect.

2. Step 2: Check the function syntax for parameters and braces

   The function must have parentheses even if there are no parameters, so fun greet { println("Hello") } is incorrect because it misses parentheses.

3. Final Answer:

   fun greet() { println("Hello") } -> Option B

4. Quick Check:

   fun + name + () + body = B [OK]

Hint: Remember: Kotlin functions start with 'fun' and need parentheses [OK]

Common Mistakes:

• Using 'function' or 'def' instead of 'fun'
• Omitting parentheses for parameter list
• Missing curly braces for function body

2. Which of the following is the correct syntax to declare a function add that takes two Int parameters and returns their sum as an Int?

easy

A. fun add(a: Int, b: Int): Int { a + b }

B. fun add(a Int, b Int): Int { return a + b }

C. fun add(a: Int, b: Int) -> Int { return a + b }

D. fun add(a: Int, b: Int): Int = a + b

Solution

1. Step 1: Check parameter declaration syntax

   Parameters must be declared as name: Type, so fun add(a Int, b Int): Int { return a + b } is incorrect because it misses colons.

2. Step 2: Verify return type and function body syntax

   fun add(a: Int, b: Int): Int = a + b uses the correct syntax with an expression body and return type. fun add(a: Int, b: Int) -> Int { return a + b } uses '->' which is invalid in Kotlin. fun add(a: Int, b: Int): Int { a + b } misses the return keyword in a block body, so it won't return the sum.

3. Final Answer:

   fun add(a: Int, b: Int): Int = a + b -> Option D

4. Quick Check:

   fun + parameters with colons + : ReturnType + = expression = A [OK]

Hint: Use colons for types and '=' for single-expression functions [OK]

Common Mistakes:

• Omitting colons between parameter names and types
• Using '->' instead of ':' for return type
• Missing 'return' in block body functions

3. What is the output of the following Kotlin code?

fun multiply(x: Int, y: Int): Int {
    return x * y
}

fun main() {
    println(multiply(3, 4))
}

medium

A. 12

B. 34

C. 7

D. Error

Solution

1. Step 1: Understand the multiply function

   The function takes two integers and returns their product using return x * y.

2. Step 2: Calculate the function call multiply(3, 4)

   3 multiplied by 4 equals 12, so the function returns 12.

3. Final Answer:

   12 -> Option A

4. Quick Check:

   3 * 4 = 12 [OK]

Hint: Multiply parameters and check return value [OK]

Common Mistakes:

• Adding instead of multiplying
• Concatenating numbers as strings
• Assuming syntax error due to missing expression body

4. Identify the error in the following Kotlin function declaration:

fun divide(a: Int, b: Int): Int {
    return a / b

medium

A. Missing closing brace '}'

B. Incorrect return type

C. Parameters should not have types

D. Function name is invalid

Solution

1. Step 1: Check function syntax completeness

   The function body starts with '{' but there is no closing '}', so the code is incomplete.

2. Step 2: Verify other syntax parts

   The return type is correct, parameters have types, and the function name is valid, so no other errors.

3. Final Answer:

   Missing closing brace '}' -> Option A

4. Quick Check:

   All blocks need matching braces [OK]

Hint: Count opening and closing braces carefully [OK]

Common Mistakes:

• Forgetting to close function body with '}'
• Misplacing colons in parameters
• Using invalid function names

5. You want to declare a Kotlin function formatName that takes two parameters: firstName and lastName (both Strings), and returns a single String in the format "Last, First". Which of the following is the correct declaration and implementation?

hard

A. fun formatName(firstName: String, lastName: String): Int = "$lastName, $firstName"

B. fun formatName(firstName String, lastName String) = lastName + ", " + firstName

C. fun formatName(firstName: String, lastName: String): String { return "$lastName, $firstName" }

D. fun formatName(firstName: String, lastName: String): String { "$lastName, $firstName" }

Solution

1. Step 1: Check parameter and return type syntax

   Parameters must use name: Type and return type must match. A uses : Int but returns String (type mismatch). B misses colons (firstName String invalid).

2. Step 2: Verify function body syntax

   C has block body { "$lastName, $firstName" } without return, returns Unit not String. D correctly uses block body with return and string interpolation.

3. Final Answer:

   fun formatName(firstName: String, lastName: String): String { return "$lastName, $firstName" } -> Option C

4. Quick Check:

   Correct types + block body with return + interpolation = D [OK]

Hint: Use return keyword in block body functions for clarity [OK]

Common Mistakes:

• Omitting return keyword in block body
• Missing return type declaration
• Incorrect string concatenation or interpolation