Named return values in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of function with named return values and naked return

What is the output of this Go program?

Go

package main
import "fmt"

func calculate() (sum int, product int) {
	sum = 3 + 4
	product = 3 * 4
	return
}

func main() {
	s, p := calculate()
	fmt.Println(s, p)
}

A 0 0

B 7 12

C 7 0

D Compilation error

💡 Hint

Named return values can be set inside the function and returned with a naked return.

The function calculate() uses named return values sum and product. They are assigned values inside the function. The naked return returns these values. So the output is '7 12'.

❓ Predict Output

intermediate

Effect of modifying named return values before return

What will this Go program print?

Go

package main
import "fmt"

func getValues() (x int, y int) {
	x = 5
	y = 10
	x += 2
	return
}

func main() {
	a, b := getValues()
	fmt.Println(a, b)
}

A 7 10

B 0 0

C 5 10

D Compilation error

💡 Hint

Named return values can be changed before the naked return statement.

The function sets x=5 and y=10, then increments x by 2 making x=7. The naked return returns x=7 and y=10.

🔧 Debug

advanced

Why does this function return zero values?

This Go function is intended to return the sum and difference of two integers using named return values. Why does it always return zero for both values? func compute(a, b int) (sum int, diff int) { return sum, diff }

Go

func compute(a, b int) (sum int, diff int) {
	return sum, diff
}

A It returns zero because named return values are ignored when explicit return values are given.

B It returns zero because the function has no return statement.

C It returns zero because the function does not assign values to sum and diff.

D It returns zero because the return statement is missing parentheses.

💡 Hint

Check how named return values interact with explicit return values.

Named return values `sum` and `diff` are zero-initialized. The function does not assign values to them before explicitly returning `sum, diff`, so zero values are returned.

📝 Syntax

advanced

Identify the syntax error with named return values

Which option contains a syntax error in this Go function with named return values?

Go

func example() (a int, b int) {
	a = 1
	b = 2
	return
}

A func example() (a int, b int) { a := 1; b := 2; return }

B func example() (a int, b int) { a = 1; b = 2; return }

C func example() (a int, b int) { a, b = 1, 2; return }

D func example() (a int, b int) { a = 1; b = 2; return a, b }

💡 Hint

Check variable declaration and assignment rules with named return values.

Option A uses ':=' to declare a and b inside the function, but a and b are already declared as named return values. Using ':=' redeclares them locally, which is not allowed here and causes a syntax error.

🚀 Application

expert

How many items are in the returned map from this function?

Consider this Go function that returns a map using named return values. How many key-value pairs does the returned map contain?

Go

func createMap() (result map[string]int) {
	result = make(map[string]int)
	for i := 0; i < 3; i++ {
		result[string('a'+i)] = i
	}
	return
}

A Compilation error

B 0

C 1

D 3

💡 Hint

The loop adds keys 'a', 'b', 'c' with values 0,1,2 to the map.

The function initializes an empty map and adds three entries with keys 'a', 'b', 'c' and values 0,1,2. So the map contains 3 key-value pairs.