Function execution flow in Go - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to call the function greet.

Go

package main
import "fmt"
func greet() {
    fmt.Println("Hello!")
}
func main() {
    [1]()
}

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

Ahello

Bgreet

Cprint

Dsay

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong function name like 'print' or 'hello'.

Forgetting the parentheses after the function name.

The function greet is called by writing its name followed by parentheses: greet().

2fill in blank

medium

Complete the code to return the sum of two integers from the function add.

Go

package main
import "fmt"
func add(a int, b int) int {
    return [1]
}
func main() {
    fmt.Println(add(3, 4))
}

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

Aa + b

Ba - b

Ca * b

Da / b

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction or multiplication instead of addition.

Forgetting to return the result.

The function should return the sum of a and b, which is a + b.

3fill in blank

hard

Fix the error in the function call to multiply.

Go

package main
import "fmt"
func multiply(x int, y int) int {
    return x * y
}
func main() {
    result := multiply[1]
    fmt.Println(result)
}

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

A(5, 6

B5, 6

C5, 6)

D(5, 6)

Attempts:

3 left

💡 Hint

Common Mistakes

Missing closing parenthesis.

Including only one parenthesis or none.

Function calls require parentheses around all arguments: multiply(5, 6).

4fill in blank

hard

Fill both blanks to create a function isEven that returns true if a number is even.

Go

package main
import "fmt"
func isEven(num int) bool {
    return num [1] 2 [2] 0
}
func main() {
    fmt.Println(isEven(4))
}

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

A%

B==

C!=

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using division (/) instead of modulus (%).

Using != instead of == for comparison.

To check if a number is even, use the modulus operator (%) to get the remainder and compare it to zero with ==.

5fill in blank

hard

Fill all three blanks to create a function filterPositive that returns a slice of positive numbers from input.

Go

package main
import "fmt"
func filterPositive(nums []int) []int {
    var result []int
    for _, [1] := range nums {
        if [2] [3] 0 {
            result = append(result, num)
        }
    }
    return result
}
func main() {
    fmt.Println(filterPositive([]int{-2, 3, 0, 5, -1}))
}

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

Anum

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong variable name in the loop or condition.

Using < instead of > in the condition.

The loop variable is num. The condition checks if num > 0 to keep positive numbers.

Practice

1. What happens when a function in Go is called?

easy

A. The code inside the function runs from top to bottom.

B. The program stops and waits for user input.

C. The function immediately returns without running any code.

D. The function runs only if it has no parameters.

Solution

1. Step 1: Understand function call behavior

   When a function is called, Go executes the code inside it in order, from the first line to the last.

2. Step 2: Eliminate incorrect options

   Options A, B, and C describe behaviors that are not how Go functions work when called.

3. Final Answer:

   The code inside the function runs from top to bottom. -> Option A

4. Quick Check:

   Function execution flow = top to bottom [OK]

Hint: Functions run code line by line when called [OK]

Common Mistakes:

• Thinking functions run only if no parameters
• Believing functions wait for user input automatically
• Assuming functions return immediately without running code

2. Which of the following is the correct way to define a function named greet that returns a string in Go?

easy

A. func greet() { return "Hello" }

B. function greet() { return "Hello" }

C. func greet() string { return "Hello" }

D. func greet() string { print("Hello") }

Solution

1. Step 1: Check Go function syntax

   In Go, functions start with func, followed by the name, parameters, and return type. func greet() string { return "Hello" } matches this.

2. Step 2: Verify return statement and type

   func greet() string { return "Hello" } returns a string and has the correct syntax. The version using 'function greet() { return "Hello" }' uses wrong keyword. The version 'func greet() { return "Hello" }' misses return type. The version using print instead of return is incorrect.

3. Final Answer:

   func greet() string { return "Hello" } -> Option C

4. Quick Check:

   Correct Go function syntax = func greet() string { return "Hello" } [OK]

Hint: Go functions start with func and specify return type [OK]

Common Mistakes:

• Using 'function' keyword instead of 'func'
• Omitting return type when function returns a value
• Using print instead of return for output

3. What is the output of this Go program?

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

medium

A. 34

B. Compilation error

C. 0

D. 7

Solution

1. Step 1: Understand function call and return

   The function add takes two integers and returns their sum. Calling add(3, 4) returns 7.

2. Step 2: Check output statement

   fmt.Println(result) prints the returned value, which is 7.

3. Final Answer:

   7 -> Option D

4. Quick Check:

   3 + 4 = 7 [OK]

Hint: Add numbers inside function, print returned result [OK]

Common Mistakes:

• Concatenating numbers as strings (34)
• Expecting zero without return
• Thinking code has syntax errors

4. Identify the error in this Go function and select the fix:

func multiply(a int, b int) int {
    product := a * b
}

func main() {
    fmt.Println(multiply(2, 3))
}

medium

A. Change function to void (no return type)

B. Add a return statement: return product

C. Remove parameters a and b

D. Replace * with + operator

Solution

1. Step 1: Check function return type and body

   The function declares it returns an int but does not have a return statement, causing a compile error.

2. Step 2: Fix by adding return statement

   Adding return product returns the calculated value, matching the function signature.

3. Final Answer:

   Add a return statement: return product -> Option B

4. Quick Check:

   Function must return value if declared [OK]

Hint: Functions with return type must return a value [OK]

Common Mistakes:

• Forgetting return statement in non-void functions
• Changing function signature unnecessarily
• Changing operators without reason

5. Given this Go code, what will be printed?

package main
import "fmt"
func process(x int) int {
    if x > 0 {
        return x * 2
    }
    return 0
}
func main() {
    values := []int{3, -1, 0, 5}
    sum := 0
    for _, v := range values {
        sum += process(v)
    }
    fmt.Println(sum)
}

hard

A. 16

B. 8

C. 0

D. Compilation error

Solution

1. Step 1: Analyze function process behavior

   For each value, if positive, returns double the value; else returns 0.

2. Step 2: Calculate sum over values slice

   Values: 3 -> 6, -1 -> 0, 0 -> 0, 5 -> 10; sum = 6 + 0 + 0 + 10 = 16.

3. Final Answer:

   16 -> Option A

4. Quick Check:

   Sum of doubled positives = 16 [OK]

Hint: Sum doubles positives, zeros for others [OK]

Common Mistakes:

• Adding negative or zero values incorrectly
• Forgetting return 0 for non-positive
• Misreading loop or function logic