Function declaration in Go - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a function named greet.

Go

func [1]() {
    fmt.Println("Hello!")
}

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

Ahello

Bprint

CsayHello

Dgreet

Attempts:

3 left

💡 Hint

Common Mistakes

Using a name that is not the function's intended name.

Forgetting to write the function name after func.

The function name is greet. This declares a function called greet that prints "Hello!".

2fill in blank

medium

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

Go

func getNumber() [1] {
    return 5
}

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

Aint

Bstring

Cbool

Dfloat64

Attempts:

3 left

💡 Hint

Common Mistakes

Using a return type that does not match the returned value.

Forgetting to specify the return type.

The function returns an integer, so the return type is int.

3fill in blank

hard

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

Go

func greet([1] string) {
    fmt.Println("Hello,", name)
}

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

Avar name

Bstring

Cname

Dgreet

Attempts:

3 left

💡 Hint

Common Mistakes

Writing the type before the parameter name.

Using keywords like var inside parameter list.

The parameter name should be name followed by its type string.

4fill in blank

hard

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

Go

func add(a [1], b [2]) int {
    return a + b
}

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

Aint

Bstring

Cfloat64

Dbool

Attempts:

3 left

💡 Hint

Common Mistakes

Using different types for parameters that are added.

Using non-integer types when integers are expected.

Both parameters are integers, so both blanks should be int.

5fill in blank

hard

Fill all three blanks to declare a function that takes a string and an int, and returns a formatted string.

Go

func formatMessage(name [1], age [2]) [3] {
    return fmt.Sprintf("%s is %d years old", name, age)
}

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

Astring

Bint

Dbool

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up parameter types.

Using wrong return type.

The function takes a string and an int, and returns a string.

Practice

1. What keyword is used to declare a function in Go?

easy

A. func

B. function

C. def

D. fun

Solution

1. Step 1: Recall Go function syntax

   In Go, functions are declared using the keyword func.

2. Step 2: Compare options

   Only func uses func, which is correct for Go.

3. Final Answer:

   func -> Option A

4. Quick Check:

   Function declaration keyword = func [OK]

Hint: Remember: Go uses 'func' to start a function [OK]

Common Mistakes:

• Using 'function' like JavaScript
• Using 'def' like Python
• Using 'fun' which is invalid

2. Which of the following is the correct syntax to declare a function named add that takes two integers and returns an integer?

easy

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

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

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

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

Solution

1. Step 1: Understand Go function parameter syntax

   In Go, parameters are declared as name type. So a int, b int is correct.

2. Step 2: Check return type and function keyword

   Function must start with func and specify return type int. func add(a int, b int) int {} matches this exactly.

3. Final Answer:

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

4. Quick Check:

   Parameter syntax = name type [OK]

Hint: Parameters: name then type, return type after parentheses [OK]

Common Mistakes:

• Putting type before name in parameters
• Using 'function' keyword instead of 'func'
• Omitting return type when needed

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

package main
import "fmt"
func multiply(x int, y int) int {
    return x * y
}
func main() {
    fmt.Println(multiply(3, 4))
}

medium

A. 12

B. 7

C. 34

D. Error

Solution

1. Step 1: Understand function call and return

   The function multiply takes two integers and returns their product.

2. Step 2: Calculate multiply(3, 4)

   3 * 4 = 12, so the function returns 12, which is printed.

3. Final Answer:

   12 -> Option A

4. Quick Check:

   3 times 4 = 12 [OK]

Hint: Multiply parameters and print result [OK]

Common Mistakes:

• Adding instead of multiplying
• Concatenating numbers as strings
• Expecting syntax error due to function

4. Identify the error in this Go function declaration:

func greet(name string) string {
    return "Hello, " + name

medium

A. Incorrect function keyword

B. Wrong parameter type

C. Missing closing brace '}'

D. Missing return type

Solution

1. Step 1: Check function syntax

   The function starts with func, has parameter and return type correctly.

2. Step 2: Look for missing parts

   The function body is missing the closing brace } to end the function.

3. Final Answer:

   Missing closing brace '}' -> Option C

4. Quick Check:

   Every function must end with '}' [OK]

Hint: Count opening and closing braces carefully [OK]

Common Mistakes:

• Forgetting to close function body with '}'
• Confusing parameter types
• Omitting return type

5. How would you declare a Go function named filterEven that takes a slice of integers and returns a new slice containing only even numbers?

hard

A. func filterEven(nums int) int {
var evens int
for _, n := range nums {
if n%2 == 0 {
evens += n
}
}
return evens
}

B. func filterEven(nums []int) []int {
var evens []int
for _, n := range nums {
if n%2 == 0 {
evens = append(evens, n)
}
}
return evens
}

C. func filterEven(nums []int) {
for _, n := range nums {
if n%2 == 0 {
fmt.Println(n)
}
}
}

D. func filterEven(nums []int) []int {
for n := range nums {
if n%2 == 0 {
return nums
}
}
return nil
}

Solution

1. Step 1: Check parameter and return types

   The function must take a slice of integers []int and return a slice of integers []int. func filterEven(nums []int) []int { var evens []int for _, n := range nums { if n%2 == 0 { evens = append(evens, n) } } return evens } matches this.

2. Step 2: Verify logic to filter even numbers

   func filterEven(nums []int) []int { var evens []int for _, n := range nums { if n%2 == 0 { evens = append(evens, n) } } return evens } creates a new slice, loops over input, appends even numbers, and returns the new slice. This is correct.

3. Final Answer:

   func filterEven(nums []int) []int { var evens []int for _, n := range nums { if n%2 == 0 { evens = append(evens, n) } } return evens } -> Option B

4. Quick Check:

   Filter slice by appending evens [OK]

Hint: Use slice, loop, append evens, return new slice [OK]

Common Mistakes:

• Wrong parameter or return types
• Returning inside loop prematurely
• Printing instead of returning filtered slice