Function parameters in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of function with multiple parameters

What is the output of this Go program?

Go

package main
import "fmt"
func addMultiply(a int, b int) (int, int) {
    return a + b, a * b
}
func main() {
    sum, product := addMultiply(3, 4)
    fmt.Println(sum, product)
}

A 7 7

B 12 7

C 7 12

D 34 12

💡 Hint

Look at the order of return values and how they are assigned.

The function returns sum first (3+4=7) and then product (3*4=12). The variables sum and product receive these values in order.

❓ Predict Output

intermediate

Output of function with variadic parameter

What does this Go program print?

Go

package main
import "fmt"
func sumAll(nums ...int) int {
    total := 0
    for _, n := range nums {
        total += n
    }
    return total
}
func main() {
    fmt.Println(sumAll(1, 2, 3, 4))
}

A 10

B 24

C Error: variadic parameter not supported

D 1234

💡 Hint

Variadic parameters allow passing any number of arguments.

The function sums all numbers: 1+2+3+4 = 10.

❓ Predict Output

advanced

Output of function with pointer parameter

What is printed by this Go program?

Go

package main
import "fmt"
func increment(x *int) {
    *x = *x + 1
}
func main() {
    a := 5
    increment(&a)
    fmt.Println(a)
}

A Compilation error

B 5

C 0

D 6

💡 Hint

The function changes the value at the pointer's address.

The function increments the value pointed by x, so a changes from 5 to 6.

❓ Predict Output

advanced

Output of function with named return parameters

What does this Go program print?

Go

package main
import "fmt"
func divide(dividend, divisor int) (result int, err string) {
    if divisor == 0 {
        err = "division by zero"
        return
    }
    result = dividend / divisor
    return
}
func main() {
    res, err := divide(10, 0)
    fmt.Println(res, err)
}

A 0

B 0 division by zero

C 10 division by zero

D runtime error: integer divide by zero

💡 Hint

Named return parameters are zero-valued if not set explicitly.

When divisor is zero, err is set but result remains zero (default int). So output is '0 division by zero'.

🧠 Conceptual

expert

Function parameter passing behavior

Which statement correctly describes how Go passes function parameters?

A Go passes parameters by value, but slices and maps behave like references.

B Go passes parameters by reference, so changes affect the caller's variables.

C Go always passes parameters by value, copying the data.

D Go uses pointers automatically for all parameters to optimize performance.

💡 Hint

Think about how slices and maps behave differently from basic types.

Go passes all parameters by value (copy). However, slices and maps contain pointers internally, so changes to their elements affect the original data.

Practice

1. What is the purpose of function parameters in Go?

easy

A. To print output from a function

B. To create new functions automatically

C. To stop a function from running

D. To send data into functions so they can use it

Solution

1. Step 1: Understand what parameters do

   Parameters let you give information to a function when you call it.

2. Step 2: Identify the correct purpose

   Sending data into functions makes them flexible and reusable with different inputs.

3. Final Answer:

   To send data into functions so they can use it -> Option D

4. Quick Check:

   Function parameters = send data into functions [OK]

Hint: Parameters pass data into functions for reuse [OK]

Common Mistakes:

• Thinking parameters create functions
• Confusing parameters with output
• Believing parameters stop function execution

2. Which of the following is the correct way to declare a function with two integer parameters in Go?

easy

A. func add(a, b int) int {}

B. func add(a int, b) int {}

C. func add(int a, int b) int {}

D. func add(a int b int) int {}

Solution

1. Step 1: Review Go function parameter syntax

   In Go, you can group parameters of the same type like a, b int.

2. Step 2: Identify correct syntax

   func add(a, b int) int {} groups same type parameters correctly. func add(a int, b) int {} misses type for b. func add(int a, int b) int {} places types before names. func add(a int b int) int {} lacks commas.

3. Final Answer:

   func add(a, b int) int {} -> Option A

4. Quick Check:

   Group same type params: a, b int [OK]

Hint: Group same type params with commas before type [OK]

Common Mistakes:

• Writing types before variable names (like C)
• Missing commas between parameters (like D)
• Forgetting type for second parameter (like B)

3. What will be the output of this Go program?

package main
import "fmt"
func greet(name string) {
    fmt.Println("Hello, " + name)
}
func main() {
    greet("Alice")
}

medium

A. Hello,

B. Hello, Alice

C. Hello, name

D. Compilation error

Solution

1. Step 1: Understand function call with parameter

   The function greet takes a string parameter name and prints "Hello, " plus that name.

2. Step 2: Check the argument passed

   In main, greet("Alice") is called, so name is "Alice".

3. Final Answer:

   Hello, Alice -> Option B

4. Quick Check:

   Function prints "Hello, " + argument [OK]

Hint: Function prints greeting plus passed name [OK]

Common Mistakes:

• Confusing parameter name with string literal
• Expecting no output
• Thinking it causes error without return

4. Identify the error in this Go function declaration:

func multiply(a int, b int) int {
    return a * b
}

func main() {
    result := multiply(3)
    fmt.Println(result)
}

medium

A. Function multiply called with wrong number of arguments

B. Missing import for fmt package

C. Return type missing in multiply function

D. Variable result not declared

Solution

1. Step 1: Check function call arguments

   The function multiply requires two int parameters, but it is called with only one argument 3.

2. Step 2: Identify the error

   This causes a compile-time error due to wrong number of arguments.

3. Final Answer:

   Function multiply called with wrong number of arguments -> Option A

4. Quick Check:

   Function call args must match parameters [OK]

Hint: Count arguments to match parameters exactly [OK]

Common Mistakes:

• Ignoring missing import for fmt (not shown here)
• Thinking return type is missing
• Assuming variable declaration error

5. Given this Go function:

func sumAndProduct(a, b int) (int, int) {
    return a + b, a * b
}

func main() {
    s, p := sumAndProduct(4, 5)
    fmt.Println(s, p)
}

What will be the output when the program runs?

hard

A. 20 9

B. 9

C. 9 20

D. Compilation error due to missing return

Solution

1. Step 1: Understand multiple return values

   The function sumAndProduct returns two integers: sum and product of a and b.

2. Step 2: Check values for inputs 4 and 5

   Sum is 4 + 5 = 9, product is 4 * 5 = 20. These are assigned to s and p.

3. Step 3: Print output

   fmt.Println(s, p) prints "9 20".

4. Final Answer:

   9 20 -> Option C

5. Quick Check:

   Multiple returns print sum then product [OK]

Hint: Multiple returns unpacked in order [OK]

Common Mistakes:

• Swapping sum and product values
• Expecting single return value
• Thinking missing return error