Why functions are needed in Go - Challenge Your Understanding

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Go program using a function?

Look at this Go program. What will it print when run?

Go

package main
import "fmt"
func greet(name string) string {
    return "Hello, " + name + "!"
}
func main() {
    message := greet("Alice")
    fmt.Println(message)
}

A Alice

B greet

C Hello, !

D Hello, Alice!

💡 Hint

The function greet returns a greeting message with the name included.

The function greet takes a name and returns a greeting string. The main function calls greet with "Alice" and prints the returned message.

🧠 Conceptual

intermediate

Why use functions in programming?

Which of these is the main reason to use functions in programs?

A To confuse the reader with extra code

B To make the program run slower

C To repeat the same code many times without rewriting it

D To avoid using variables

💡 Hint

Think about how functions help with repeating tasks.

Functions let you write code once and use it many times, making programs shorter and easier to manage.

❓ Predict Output

advanced

What is the output of this Go program with multiple function calls?

What will this Go program print when run?

Go

package main
import "fmt"
func add(a, b int) int {
    return a + b
}
func main() {
    x := add(2, 3)
    y := add(x, 4)
    fmt.Println(y)
}

A 7

B 9

C 5

D Error

💡 Hint

Add the numbers step by step.

First add(2,3) returns 5, then add(5,4) returns 9, which is printed.

🔧 Debug

advanced

What error does this Go program cause?

This Go program tries to use a function but has a problem. What error will it cause?

Go

package main
import "fmt"
func multiply(a int, b int) int {
    return a * b
}
func main() {
    result := multiply(3)
    fmt.Println(result)
}

A compile error: missing argument for multiply

B prints 3

C runtime error: nil pointer dereference

D prints 0

💡 Hint

Check how many arguments the multiply function needs.

The multiply function requires two arguments, but only one is given, causing a compile error.

🚀 Application

expert

How many times is the function called in this Go program?

Count how many times the function 'countCalls' is called when this program runs.

Go

package main
import "fmt"
var calls int
func countCalls() {
    calls++
}
func main() {
    for i := 0; i < 3; i++ {
        countCalls()
    }
    if calls > 0 {
        countCalls()
    }
    fmt.Println(calls)
}

A 4

B 3

C 1

D 0

💡 Hint

Count calls inside the loop and the one after the loop.

The function is called 3 times in the loop and once more after, totaling 4 calls.